Press n or j to go to the next uncovered block, b, p or k for the previous block.
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/** @import { Visitors } from 'zimmerframe' */
/** @import { ComponentAnalysis } from '../phases/types.js' */
/** @import { Scope, ScopeRoot } from '../phases/scope.js' */
/** @import { AST, Binding, SvelteNode, ValidatedCompileOptions } from '#compiler' */
import MagicString from 'magic-string';
import { walk } from 'zimmerframe';
import { parse } from '../phases/1-parse/index.js';
import { regex_valid_component_name } from '../phases/1-parse/state/element.js';
import { analyze_component } from '../phases/2-analyze/index.js';
import { get_rune } from '../phases/scope.js';
import { reset, reset_warning_filter } from '../state.js';
import {
extract_identifiers,
extract_all_identifiers_from_expression,
is_text_attribute
} from '../utils/ast.js';
import { migrate_svelte_ignore } from '../utils/extract_svelte_ignore.js';
import { validate_component_options } from '../validate-options.js';
import { is_svg, is_void } from '../../utils.js';
import { regex_is_valid_identifier } from '../phases/patterns.js';
const regex_style_tags = /(<style[^>]+>)([\S\s]*?)(<\/style>)/g;
const style_placeholder = '/*$$__STYLE_CONTENT__$$*/';
let has_migration_task = false;
/**
* Does a best-effort migration of Svelte code towards using runes, event attributes and render tags.
* May throw an error if the code is too complex to migrate automatically.
*
* @param {string} source
* @param {{filename?: string}} [options]
* @returns {{ code: string; }}
*/
export function migrate(source, { filename } = {}) {
let og_source = source;
try {
has_migration_task = false;
// Blank CSS, could contain SCSS or similar that needs a preprocessor.
// Since we don't care about CSS in this migration, we'll just ignore it.
/** @type {Array<[number, string]>} */
const style_contents = [];
source = source.replace(regex_style_tags, (_, start, content, end, idx) => {
style_contents.push([idx + start.length, content]);
return start + style_placeholder + end;
});
reset_warning_filter(() => false);
reset(source, { filename: filename ?? '(unknown)' });
let parsed = parse(source);
const { customElement: customElementOptions, ...parsed_options } = parsed.options || {};
/** @type {ValidatedCompileOptions} */
const combined_options = {
...validate_component_options({}, ''),
...parsed_options,
customElementOptions,
filename: filename ?? '(unknown)'
};
const str = new MagicString(source);
const analysis = analyze_component(parsed, source, combined_options);
const indent = guess_indent(source);
str.replaceAll(/(<svelte:options\s.*?\s?)accessors\s?/g, (_, $1) => $1);
for (const content of style_contents) {
str.overwrite(content[0], content[0] + style_placeholder.length, content[1]);
}
/** @type {State} */
let state = {
scope: analysis.instance.scope,
analysis,
filename,
str,
indent,
props: [],
props_insertion_point: parsed.instance?.content.start ?? 0,
has_props_rune: false,
end: source.length,
names: {
props: analysis.root.unique('props').name,
rest: analysis.root.unique('rest').name,
// event stuff
run: analysis.root.unique('run').name,
handlers: analysis.root.unique('handlers').name,
stopImmediatePropagation: analysis.root.unique('stopImmediatePropagation').name,
preventDefault: analysis.root.unique('preventDefault').name,
stopPropagation: analysis.root.unique('stopPropagation').name,
once: analysis.root.unique('once').name,
self: analysis.root.unique('self').name,
trusted: analysis.root.unique('trusted').name,
createBubbler: analysis.root.unique('createBubbler').name,
bubble: analysis.root.unique('bubble').name,
passive: analysis.root.unique('passive').name,
nonpassive: analysis.root.unique('nonpassive').name
},
legacy_imports: new Set(),
script_insertions: new Set(),
derived_components: new Map(),
derived_labeled_statements: new Set(),
has_svelte_self: false
};
if (parsed.module) {
const context = parsed.module.attributes.find((attr) => attr.name === 'context');
if (context) {
state.str.update(context.start, context.end, 'module');
}
}
if (parsed.instance) {
walk(parsed.instance.content, state, instance_script);
}
state = { ...state, scope: analysis.template.scope };
walk(parsed.fragment, state, template);
let insertion_point = parsed.instance
? /** @type {number} */ (parsed.instance.content.start)
: 0;
const need_script =
state.legacy_imports.size > 0 ||
state.derived_components.size > 0 ||
state.script_insertions.size > 0 ||
state.props.length > 0 ||
analysis.uses_rest_props ||
analysis.uses_props ||
state.has_svelte_self;
if (!parsed.instance && need_script) {
str.appendRight(0, '<script>');
}
if (state.has_svelte_self && filename) {
const file = filename.split('/').pop();
str.appendRight(
insertion_point,
`\n${indent}import ${state.analysis.name} from './${file}';`
);
}
const specifiers = [...state.legacy_imports].map((imported) => {
const local = state.names[imported];
return imported === local ? imported : `${imported} as ${local}`;
});
const legacy_import = `import { ${specifiers.join(', ')} } from 'svelte/legacy';\n`;
if (state.legacy_imports.size > 0) {
str.appendRight(insertion_point, `\n${indent}${legacy_import}`);
}
if (state.script_insertions.size > 0) {
str.appendRight(
insertion_point,
`\n${indent}${[...state.script_insertions].join(`\n${indent}`)}`
);
}
insertion_point = state.props_insertion_point;
if (state.props.length > 0 || analysis.uses_rest_props || analysis.uses_props) {
const has_many_props = state.props.length > 3;
const newline_separator = `\n${indent}${indent}`;
const props_separator = has_many_props ? newline_separator : ' ';
let props = '';
if (analysis.uses_props) {
props = `...${state.names.props}`;
} else {
props = state.props
.filter((prop) => !prop.type_only)
.map((prop) => {
let prop_str =
prop.local === prop.exported ? prop.local : `${prop.exported}: ${prop.local}`;
if (prop.bindable) {
prop_str += ` = $bindable(${prop.init})`;
} else if (prop.init) {
prop_str += ` = ${prop.init}`;
}
return prop_str;
})
.join(`,${props_separator}`);
if (analysis.uses_rest_props) {
props += `${state.props.length > 0 ? `,${props_separator}` : ''}...${state.names.rest}`;
}
}
if (state.has_props_rune) {
// some render tags or forwarded event attributes to add
str.appendRight(insertion_point, ` ${props},`);
} else {
const uses_ts = parsed.instance?.attributes.some(
(attr) => attr.name === 'lang' && /** @type {any} */ (attr).value[0].data === 'ts'
);
const type_name = state.scope.root.unique('Props').name;
let type = '';
if (uses_ts) {
type = `interface ${type_name} {${newline_separator}${state.props
.map((prop) => {
const comment = prop.comment ? `${prop.comment}${newline_separator}` : '';
return `${comment}${prop.exported}${prop.optional ? '?' : ''}: ${prop.type};`;
})
.join(newline_separator)}`;
if (analysis.uses_props || analysis.uses_rest_props) {
type += `${state.props.length > 0 ? newline_separator : ''}[key: string]: any`;
}
type += `\n${indent}}`;
} else {
type = `/**\n${indent} * @typedef {Object} ${type_name}${state.props
.map((prop) => {
return `\n${indent} * @property {${prop.type}} ${prop.optional ? `[${prop.exported}]` : prop.exported}${prop.comment ? ` - ${prop.comment}` : ''}`;
})
.join(``)}\n${indent} */`;
}
let props_declaration = `let {${props_separator}${props}${has_many_props ? `\n${indent}` : ' '}}`;
if (uses_ts) {
props_declaration = `${type}\n\n${indent}${props_declaration}`;
props_declaration = `${props_declaration}${type ? `: ${type_name}` : ''} = $props();`;
} else {
props_declaration = `${type && state.props.length > 0 ? `${type}\n\n${indent}` : ''}/** @type {${state.props.length > 0 ? type_name : ''}${analysis.uses_props || analysis.uses_rest_props ? `${state.props.length > 0 ? ' & ' : ''}{ [key: string]: any }` : ''}} */\n${indent}${props_declaration}`;
props_declaration = `${props_declaration} = $props();`;
}
props_declaration = `\n${indent}${props_declaration}`;
str.appendRight(insertion_point, props_declaration);
}
}
/**
* If true, then we need to move all reactive statements to the end of the script block,
* in their correct order. Svelte 4 reordered reactive statements, $derived/$effect.pre
* don't have this behavior.
*/
let needs_reordering = false;
for (const [node, { dependencies }] of state.analysis.reactive_statements) {
/** @type {Binding[]} */
let ids = [];
if (
node.body.type === 'ExpressionStatement' &&
node.body.expression.type === 'AssignmentExpression'
) {
ids = extract_identifiers(node.body.expression.left)
.map((id) => state.scope.get(id.name))
.filter((id) => !!id);
}
if (
dependencies.some(
(dep) =>
!ids.includes(dep) &&
(dep.kind === 'prop' || dep.kind === 'bindable_prop'
? state.props_insertion_point
: /** @type {number} */ (dep.node.start)) > /** @type {number} */ (node.start)
)
) {
needs_reordering = true;
break;
}
}
if (needs_reordering) {
const nodes = Array.from(state.analysis.reactive_statements.keys());
for (const node of nodes) {
const { start, end } = get_node_range(source, node);
str.appendLeft(end, '\n');
str.move(start, end, /** @type {number} */ (parsed.instance?.content.end));
str.update(start - (source[start - 2] === '\r' ? 2 : 1), start, '');
}
}
insertion_point = parsed.instance
? /** @type {number} */ (parsed.instance.content.end)
: insertion_point;
if (state.derived_components.size > 0) {
str.appendRight(
insertion_point,
`\n${indent}${[...state.derived_components.entries()].map(([init, name]) => `const ${name} = $derived(${init});`).join(`\n${indent}`)}\n`
);
}
if (state.props.length > 0 && state.analysis.accessors) {
str.appendRight(
insertion_point,
`\n${indent}export {${state.props.reduce((acc, prop) => (prop.slot_name || prop.type_only ? acc : `${acc}\n${indent}\t${prop.local},`), '')}\n${indent}}\n`
);
}
if (!parsed.instance && need_script) {
str.appendRight(insertion_point, '\n</script>\n\n');
}
return { code: str.toString() };
} catch (e) {
// eslint-disable-next-line no-console
console.error('Error while migrating Svelte code', e);
has_migration_task = true;
return {
code: `<!-- @migration-task Error while migrating Svelte code: ${/** @type {any} */ (e).message} -->\n${og_source}`
};
} finally {
if (has_migration_task) {
// eslint-disable-next-line no-console
console.log(
`One or more \`@migration-task\` comments were added to ${filename ? `\`${filename}\`` : "a file (unfortunately we don't know the name)"}, please check them and complete the migration manually.`
);
}
}
}
/**
* @typedef {{
* scope: Scope;
* str: MagicString;
* analysis: ComponentAnalysis;
* filename?: string;
* indent: string;
* props: Array<{ local: string; exported: string; init: string; bindable: boolean; slot_name?: string; optional: boolean; type: string; comment?: string; type_only?: boolean; needs_refine_type?: boolean; }>;
* props_insertion_point: number;
* has_props_rune: boolean;
* end: number;
* names: Record<string, string>;
* legacy_imports: Set<string>;
* script_insertions: Set<string>;
* derived_components: Map<string, string>;
* derived_labeled_statements: Set<LabeledStatement>;
* has_svelte_self: boolean;
* }} State
*/
/** @type {Visitors<SvelteNode, State>} */
const instance_script = {
_(node, { state, next }) {
// @ts-expect-error
const comments = node.leadingComments;
if (comments) {
for (const comment of comments) {
if (comment.type === 'Line') {
const migrated = migrate_svelte_ignore(comment.value);
if (migrated !== comment.value) {
state.str.overwrite(comment.start + '//'.length, comment.end, migrated);
}
}
}
}
next();
},
Identifier(node, { state, path }) {
handle_identifier(node, state, path);
},
ImportDeclaration(node, { state }) {
state.props_insertion_point = node.end ?? state.props_insertion_point;
if (node.source.value === 'svelte') {
let illegal_specifiers = [];
let removed_specifiers = 0;
for (let specifier of node.specifiers) {
if (
specifier.type === 'ImportSpecifier' &&
['beforeUpdate', 'afterUpdate'].includes(specifier.imported.name)
) {
const references = state.scope.references.get(specifier.local.name);
if (!references) {
let end = /** @type {number} */ (
state.str.original.indexOf(',', specifier.end) !== -1 &&
state.str.original.indexOf(',', specifier.end) <
state.str.original.indexOf('}', specifier.end)
? state.str.original.indexOf(',', specifier.end) + 1
: specifier.end
);
while (state.str.original[end].trim() === '') end++;
state.str.remove(/** @type {number} */ (specifier.start), end);
removed_specifiers++;
continue;
}
illegal_specifiers.push(specifier.imported.name);
}
}
if (removed_specifiers === node.specifiers.length) {
state.str.remove(/** @type {number} */ (node.start), /** @type {number} */ (node.end));
}
if (illegal_specifiers.length > 0) {
throw new Error(
`Can't migrate code with ${illegal_specifiers.join(' and ')}. Please migrate by hand.`
);
}
}
},
ExportNamedDeclaration(node, { state, next }) {
if (node.declaration) {
next();
return;
}
let count_removed = 0;
for (const specifier of node.specifiers) {
const binding = state.scope.get(specifier.local.name);
if (binding?.kind === 'bindable_prop') {
state.str.remove(
/** @type {number} */ (specifier.start),
/** @type {number} */ (specifier.end)
);
count_removed++;
}
}
if (count_removed === node.specifiers.length) {
state.str.remove(/** @type {number} */ (node.start), /** @type {number} */ (node.end));
}
},
VariableDeclaration(node, { state, path, visit, next }) {
if (state.scope !== state.analysis.instance.scope) {
return;
}
let nr_of_props = 0;
for (const declarator of node.declarations) {
if (state.analysis.runes) {
if (get_rune(declarator.init, state.scope) === '$props') {
state.props_insertion_point = /** @type {number} */ (declarator.id.start) + 1;
state.has_props_rune = true;
}
continue;
}
let bindings;
try {
bindings = state.scope.get_bindings(declarator);
} catch (e) {
// no bindings, so we can skip this
next();
continue;
}
const has_state = bindings.some((binding) => binding.kind === 'state');
const has_props = bindings.some((binding) => binding.kind === 'bindable_prop');
if (!has_state && !has_props) {
next();
continue;
}
if (has_props) {
nr_of_props++;
if (declarator.id.type !== 'Identifier') {
// TODO invest time in this?
throw new Error(
'Encountered an export declaration pattern that is not supported for automigration.'
);
// Turn export let into props. It's really really weird because export let { x: foo, z: [bar]} = ..
// means that foo and bar are the props (i.e. the leafs are the prop names), not x and z.
// const tmp = state.scope.generate('tmp');
// const paths = extract_paths(declarator.id);
// state.props_pre.push(
// b.declaration('const', b.id(tmp), visit(declarator.init!) as Expression)
// );
// for (const path of paths) {
// const name = (path.node as Identifier).name;
// const binding = state.scope.get(name)!;
// const value = path.expression!(b.id(tmp));
// if (binding.kind === 'bindable_prop' || binding.kind === 'rest_prop') {
// state.props.push({
// local: name,
// exported: binding.prop_alias ? binding.prop_alias : name,
// init: value
// });
// state.props_insertion_point = /** @type {number} */(declarator.end);
// } else {
// declarations.push(b.declarator(path.node, value));
// }
// }
}
const name = declarator.id.name;
const binding = /** @type {Binding} */ (state.scope.get(name));
if (state.analysis.uses_props && (declarator.init || binding.updated)) {
throw new Error(
'$$props is used together with named props in a way that cannot be automatically migrated.'
);
}
const prop = state.props.find((prop) => prop.exported === (binding.prop_alias || name));
if (prop) {
next();
// $$Props type was used
prop.init = declarator.init
? state.str
.snip(
/** @type {number} */ (declarator.init.start),
/** @type {number} */ (declarator.init.end)
)
.toString()
: '';
prop.bindable = binding.updated;
prop.exported = binding.prop_alias || name;
prop.type_only = false;
} else {
next();
state.props.push({
local: name,
exported: binding.prop_alias ? binding.prop_alias : name,
init: declarator.init
? state.str
.snip(
/** @type {number} */ (declarator.init.start),
/** @type {number} */ (declarator.init.end)
)
.toString()
: '',
optional: !!declarator.init,
bindable: binding.updated,
...extract_type_and_comment(declarator, state.str, path)
});
}
state.props_insertion_point = /** @type {number} */ (declarator.end);
state.str.update(
/** @type {number} */ (declarator.start),
/** @type {number} */ (declarator.end),
''
);
continue;
}
// state
if (declarator.init) {
let { start, end } = /** @type {{ start: number, end: number }} */ (declarator.init);
if (declarator.init.type === 'SequenceExpression') {
while (state.str.original[start] !== '(') start -= 1;
while (state.str.original[end - 1] !== ')') end += 1;
}
state.str.prependLeft(start, '$state(');
state.str.appendRight(end, ')');
} else {
/**
* @type {AssignmentExpression | undefined}
*/
let assignment_in_labeled;
/**
* @type {LabeledStatement | undefined}
*/
let labeled_statement;
// Analyze declaration bindings to see if they're exclusively updated within a single reactive statement
const possible_derived = bindings.every((binding) =>
binding.references.every((reference) => {
const declaration = reference.path.find((el) => el.type === 'VariableDeclaration');
const assignment = reference.path.find((el) => el.type === 'AssignmentExpression');
const update = reference.path.find((el) => el.type === 'UpdateExpression');
const labeled = reference.path.find(
(el) => el.type === 'LabeledStatement' && el.label.name === '$'
);
if (assignment && labeled) {
if (assignment_in_labeled) return false;
assignment_in_labeled = /** @type {AssignmentExpression} */ (assignment);
labeled_statement = /** @type {LabeledStatement} */ (labeled);
}
return (
!update &&
((declaration && binding.initial) ||
(labeled && assignment) ||
(!labeled && !assignment))
);
})
);
const labeled_has_single_assignment =
labeled_statement?.body.type === 'BlockStatement' &&
labeled_statement.body.body.length === 1 &&
labeled_statement.body.body[0].type === 'ExpressionStatement';
const is_expression_assignment =
labeled_statement?.body.type === 'ExpressionStatement' &&
labeled_statement.body.expression.type === 'AssignmentExpression';
let should_be_state = false;
if (is_expression_assignment) {
const body = /**@type {ExpressionStatement}*/ (labeled_statement?.body);
const expression = /**@type {AssignmentExpression}*/ (body.expression);
const [, ids] = extract_all_identifiers_from_expression(expression.right);
if (ids.length === 0) {
should_be_state = true;
state.derived_labeled_statements.add(
/** @type {LabeledStatement} */ (labeled_statement)
);
}
}
if (
!should_be_state &&
possible_derived &&
assignment_in_labeled &&
labeled_statement &&
(labeled_has_single_assignment || is_expression_assignment)
) {
const indent = state.str.original.substring(
state.str.original.lastIndexOf('\n', /** @type {number} */ (node.start)) + 1,
/** @type {number} */ (node.start)
);
// transfer all the leading comments
if (
labeled_statement.body.type === 'BlockStatement' &&
labeled_statement.body.body[0].leadingComments
) {
for (let comment of labeled_statement.body.body[0].leadingComments) {
state.str.prependLeft(
/** @type {number} */ (node.start),
comment.type === 'Block'
? `/*${comment.value}*/\n${indent}`
: `// ${comment.value}\n${indent}`
);
}
}
// Someone wrote a `$: { ... }` statement which we can turn into a `$derived`
state.str.appendRight(
/** @type {number} */ (declarator.id.typeAnnotation?.end ?? declarator.id.end),
' = $derived('
);
visit(assignment_in_labeled.right);
state.str.appendRight(
/** @type {number} */ (declarator.id.typeAnnotation?.end ?? declarator.id.end),
state.str
.snip(
/** @type {number} */ (assignment_in_labeled.right.start),
/** @type {number} */ (assignment_in_labeled.right.end)
)
.toString()
);
state.str.remove(
/** @type {number} */ (labeled_statement.start),
/** @type {number} */ (labeled_statement.end)
);
state.str.appendRight(
/** @type {number} */ (declarator.id.typeAnnotation?.end ?? declarator.id.end),
')'
);
state.derived_labeled_statements.add(labeled_statement);
// transfer all the trailing comments
if (
labeled_statement.body.type === 'BlockStatement' &&
labeled_statement.body.body[0].trailingComments
) {
for (let comment of labeled_statement.body.body[0].trailingComments) {
state.str.appendRight(
/** @type {number} */ (declarator.id.typeAnnotation?.end ?? declarator.id.end),
comment.type === 'Block'
? `\n${indent}/*${comment.value}*/`
: `\n${indent}// ${comment.value}`
);
}
}
} else {
state.str.prependLeft(
/** @type {number} */ (declarator.id.typeAnnotation?.end ?? declarator.id.end),
' = $state('
);
if (should_be_state) {
// someone wrote a `$: foo = ...` statement which we can turn into `let foo = $state(...)`
state.str.appendRight(
/** @type {number} */ (declarator.id.typeAnnotation?.end ?? declarator.id.end),
state.str
.snip(
/** @type {number} */ (
/** @type {AssignmentExpression} */ (assignment_in_labeled).right.start
),
/** @type {number} */ (
/** @type {AssignmentExpression} */ (assignment_in_labeled).right.end
)
)
.toString()
);
state.str.remove(
/** @type {number} */ (/** @type {LabeledStatement} */ (labeled_statement).start),
/** @type {number} */ (/** @type {LabeledStatement} */ (labeled_statement).end)
);
}
state.str.appendRight(
/** @type {number} */ (declarator.id.typeAnnotation?.end ?? declarator.id.end),
')'
);
}
}
}
if (nr_of_props === node.declarations.length) {
let start = /** @type {number} */ (node.start);
let end = /** @type {number} */ (node.end);
const parent = path.at(-1);
if (parent?.type === 'ExportNamedDeclaration') {
start = /** @type {number} */ (parent.start);
end = /** @type {number} */ (parent.end);
}
while (state.str.original[start] !== '\n') start--;
while (state.str.original[end] !== '\n') end++;
state.str.update(start, end, '');
}
},
BreakStatement(node, { state, path }) {
if (path[1].type !== 'LabeledStatement') return;
if (node.label?.name !== '$') return;
state.str.update(
/** @type {number} */ (node.start),
/** @type {number} */ (node.end),
'return;'
);
},
LabeledStatement(node, { path, state, next }) {
if (state.analysis.runes) return;
if (path.length > 1) return;
if (node.label.name !== '$') return;
if (state.derived_labeled_statements.has(node)) return;
next();
if (
node.body.type === 'ExpressionStatement' &&
node.body.expression.type === 'AssignmentExpression'
) {
const ids = extract_identifiers(node.body.expression.left);
const [, expression_ids] = extract_all_identifiers_from_expression(
node.body.expression.right
);
const bindings = ids.map((id) => state.scope.get(id.name));
const reassigned_bindings = bindings.filter((b) => b?.reassigned);
if (reassigned_bindings.length === 0 && !bindings.some((b) => b?.kind === 'store_sub')) {
let { start, end } = /** @type {{ start: number, end: number }} */ (
node.body.expression.right
);
// $derived
state.str.update(
/** @type {number} */ (node.start),
/** @type {number} */ (node.body.expression.start),
'let '
);
if (node.body.expression.right.type === 'SequenceExpression') {
while (state.str.original[start] !== '(') start -= 1;
while (state.str.original[end - 1] !== ')') end += 1;
}
state.str.prependRight(start, `$derived(`);
// in a case like `$: ({ a } = b())`, there's already a trailing parenthesis.
// otherwise, we need to add one
if (state.str.original[/** @type {number} */ (node.body.start)] !== '(') {
state.str.appendLeft(end, `)`);
}
return;
} else {
for (const binding of reassigned_bindings) {
if (binding && (ids.includes(binding.node) || expression_ids.length === 0)) {
const init =
binding.kind === 'state'
? ' = $state()'
: expression_ids.length === 0
? ` = $state(${state.str.original.substring(/** @type {number} */ (node.body.expression.right.start), node.body.expression.right.end)})`
: '';
// implicitly-declared variable which we need to make explicit
state.str.prependLeft(
/** @type {number} */ (node.start),
`let ${binding.node.name}${init};\n${state.indent}`
);
}
}
if (expression_ids.length === 0 && !bindings.some((b) => b?.kind === 'store_sub')) {
state.str.remove(/** @type {number} */ (node.start), /** @type {number} */ (node.end));
return;
}
}
}
state.legacy_imports.add('run');
const is_block_stmt = node.body.type === 'BlockStatement';
const start_end = /** @type {number} */ (node.body.start);
// TODO try to find out if we can use $derived.by instead?
if (is_block_stmt) {
state.str.update(
/** @type {number} */ (node.start),
start_end + 1,
`${state.names.run}(() => {`
);
const end = /** @type {number} */ (node.body.end);
state.str.update(end - 1, end, '});');
} else {
state.str.update(
/** @type {number} */ (node.start),
start_end,
`${state.names.run}(() => {\n${state.indent}`
);
state.str.indent(state.indent, {
exclude: [
[0, /** @type {number} */ (node.body.start)],
[/** @type {number} */ (node.body.end), state.end]
]
});
state.str.appendLeft(/** @type {number} */ (node.end), `\n${state.indent}});`);
}
}
};
/** @type {Visitors<SvelteNode, State>} */
const template = {
Identifier(node, { state, path }) {
handle_identifier(node, state, path);
},
RegularElement(node, { state, path, next }) {
migrate_slot_usage(node, path, state);
handle_events(node, state);
// Strip off any namespace from the beginning of the node name.
const node_name = node.name.replace(/[a-zA-Z-]*:/g, '');
if (state.analysis.source[node.end - 2] === '/' && !is_void(node_name) && !is_svg(node_name)) {
let trimmed_position = node.end - 2;
while (state.str.original.charAt(trimmed_position - 1) === ' ') trimmed_position--;
state.str.remove(trimmed_position, node.end - 1);
state.str.appendRight(node.end, `</${node.name}>`);
}
next();
},
SvelteSelf(node, { state, next }) {
const source = state.str.original.substring(node.start, node.end);
if (!state.filename) {
const indent = guess_indent(source);
has_migration_task = true;
state.str.prependRight(
node.start,
`<!-- @migration-task: svelte:self is deprecated, import this Svelte file into itself instead -->\n${indent}`
);
next();
return;
}
// overwrite the open tag
state.str.overwrite(
node.start + 1,
node.start + 1 + 'svelte:self'.length,
`${state.analysis.name}`
);
// if it has a fragment we need to overwrite the closing tag too
if (node.fragment.nodes.length > 0) {
state.str.overwrite(
state.str.original.lastIndexOf('<', node.end) + 2,
node.end - 1,
`${state.analysis.name}`
);
} else if (!source.endsWith('/>')) {
// special case for case `<svelte:self></svelte:self>` it has no fragment but
// we still need to overwrite the end tag
state.str.overwrite(
node.start + source.lastIndexOf('</', node.end) + 2,
node.end - 1,
`${state.analysis.name}`
);
}
state.has_svelte_self = true;
next();
},
SvelteElement(node, { state, path, next }) {
migrate_slot_usage(node, path, state);
if (node.tag.type === 'Literal') {
let is_static = true;
let a = /** @type {number} */ (node.tag.start);
let b = /** @type {number} */ (node.tag.end);
let quote_mark = state.str.original[a - 1];
while (state.str.original[--a] !== '=') {
if (state.str.original[a] === '{') {
is_static = false;
break;
}
}
if (is_static && state.str.original[b] === quote_mark) {
state.str.prependLeft(a + 1, '{');
state.str.appendRight(/** @type {number} */ (node.tag.end) + 1, '}');
}
}
handle_events(node, state);
next();
},
Component(node, { state, path, next }) {
next();
migrate_slot_usage(node, path, state);
},
SvelteComponent(node, { state, next, path }) {
next();
migrate_slot_usage(node, path, state);
let expression = state.str
.snip(
/** @type {number} */ (node.expression.start),
/** @type {number} */ (node.expression.end)
)
.toString();
if (
(node.expression.type !== 'Identifier' && node.expression.type !== 'MemberExpression') ||
!regex_valid_component_name.test(expression)
) {
let current_expression = expression;
expression = state.scope.generate('SvelteComponent');
let needs_derived = true;
for (let i = path.length - 1; i >= 0; i--) {
const part = path[i];
if (
part.type === 'EachBlock' ||
part.type === 'AwaitBlock' ||
part.type === 'IfBlock' ||
part.type === 'SnippetBlock' ||
part.type === 'Component' ||
part.type === 'SvelteComponent'
) {
let position = node.start;
if (i !== path.length - 1) {
for (let modifier = 1; modifier < path.length - i; modifier++) {
const path_part = path[i + modifier];
if ('start' in path_part) {
position = /** @type {number} */ (path_part.start);
break;
}
}
}
const indent = state.str.original.substring(
state.str.original.lastIndexOf('\n', position) + 1,
position
);
state.str.appendRight(
position,
`{@const ${expression} = ${current_expression}}\n${indent}`
);
needs_derived = false;
break;
}
}
if (needs_derived) {
if (state.derived_components.has(current_expression)) {
expression = /** @type {string} */ (state.derived_components.get(current_expression));
} else {
state.derived_components.set(current_expression, expression);
}
}
}
state.str.overwrite(node.start + 1, node.start + node.name.length + 1, expression);
if (state.str.original.substring(node.end - node.name.length - 1, node.end - 1) === node.name) {
state.str.overwrite(node.end - node.name.length - 1, node.end - 1, expression);
}
let this_pos = state.str.original.lastIndexOf('this', node.expression.start);
while (!state.str.original.charAt(this_pos - 1).trim()) this_pos--;
const end_pos = state.str.original.indexOf('}', node.expression.end) + 1;
state.str.remove(this_pos, end_pos);
},
SvelteFragment(node, { state, path, next }) {
migrate_slot_usage(node, path, state);
next();
},
SvelteWindow(node, { state, next }) {
handle_events(node, state);
next();
},
SvelteBody(node, { state, next }) {
handle_events(node, state);
next();
},
SvelteDocument(node, { state, next }) {
handle_events(node, state);
next();
},
SlotElement(node, { state, path, next, visit }) {
migrate_slot_usage(node, path, state);
if (state.analysis.custom_element) return;
let name = 'children';
let slot_name = 'default';
let slot_props = '{ ';
for (const attr of node.attributes) {
if (attr.type === 'SpreadAttribute') {
slot_props += `...${state.str.original.substring(/** @type {number} */ (attr.expression.start), attr.expression.end)}, `;
} else if (attr.type === 'Attribute') {
if (attr.name === 'slot') {
continue;
}
if (attr.name === 'name') {
slot_name = /** @type {any} */ (attr.value)[0].data;
} else {
const attr_value =
attr.value === true || Array.isArray(attr.value) ? attr.value : [attr.value];
let value = 'true';
if (attr_value !== true) {
const first = attr_value[0];
const last = attr_value[attr_value.length - 1];
for (const attr of attr_value) {
visit(attr);
}
value = state.str
.snip(
first.type === 'Text'
? first.start - 1
: /** @type {number} */ (first.expression.start),
last.type === 'Text' ? last.end + 1 : /** @type {number} */ (last.expression.end)
)
.toString();
}
slot_props += value === attr.name ? `${value}, ` : `${attr.name}: ${value}, `;
}
}
}
slot_props += '}';
if (slot_props === '{ }') {
slot_props = '';
}
const existing_prop = state.props.find((prop) => prop.slot_name === slot_name);
if (existing_prop) {
name = existing_prop.local;
} else if (slot_name !== 'default') {
name = state.scope.generate(slot_name);
if (name !== slot_name) {
throw new Error(
'This migration would change the name of a slot making the component unusable'
);
}
}
if (!existing_prop) {
state.props.push({
local: name,
exported: name,
init: '',
bindable: false,
optional: true,
slot_name,
type: `import('svelte').${slot_props ? 'Snippet<[any]>' : 'Snippet'}`
});
} else if (existing_prop.needs_refine_type) {
existing_prop.type = `import('svelte').${slot_props ? 'Snippet<[any]>' : 'Snippet'}`;
existing_prop.needs_refine_type = false;
}
if (node.fragment.nodes.length > 0) {
next();
state.str.update(
node.start,
node.fragment.nodes[0].start,
`{#if ${name}}{@render ${state.analysis.uses_props ? `${state.names.props}.` : ''}${name}(${slot_props})}{:else}`
);
state.str.update(node.fragment.nodes[node.fragment.nodes.length - 1].end, node.end, '{/if}');
} else {
state.str.update(
node.start,
node.end,
`{@render ${state.analysis.uses_props ? `${state.names.props}.` : ''}${name}?.(${slot_props})}`
);
}
},
Comment(node, { state }) {
const migrated = migrate_svelte_ignore(node.data);
if (migrated !== node.data) {
state.str.overwrite(node.start + '<!--'.length, node.end - '-->'.length, migrated);
}
}
};
/**
* @param {AST.RegularElement | AST.SvelteElement | AST.SvelteComponent | AST.Component | AST.SlotElement | AST.SvelteFragment} node
* @param {SvelteNode[]} path
* @param {State} state
*/
function migrate_slot_usage(node, path, state) {
const parent = path.at(-2);
// Bail on custom element slot usage
if (
parent?.type !== 'Component' &&
parent?.type !== 'SvelteComponent' &&
node.type !== 'Component' &&
node.type !== 'SvelteComponent'
) {
return;
}
let snippet_name = 'children';
let snippet_props = [];
// if we stop the transform because the name is not correct we don't want to
// remove the let directive and they could come before the name
let removal_queue = [];
for (let attribute of node.attributes) {
if (
attribute.type === 'Attribute' &&
attribute.name === 'slot' &&
is_text_attribute(attribute)
) {
snippet_name = attribute.value[0].data;
if (!regex_is_valid_identifier.test(snippet_name)) {
has_migration_task = true;
state.str.appendLeft(
node.start,
`<!-- @migration-task: migrate this slot by hand, \`${snippet_name}\` is an invalid identifier -->\n${state.indent}`
);
return;
}
if (parent?.type === 'Component' || parent?.type === 'SvelteComponent') {
for (let attribute of parent.attributes) {
if (attribute.type === 'Attribute' || attribute.type === 'BindDirective') {
if (attribute.name === snippet_name) {
state.str.appendLeft(
node.start,
`<!-- @migration-task: migrate this slot by hand, \`${snippet_name}\` would shadow a prop on the parent component -->\n${state.indent}`
);
return;
}
}
}
}
// flush the queue after we found the name
for (let remove_let of removal_queue) {
remove_let();
}
state.str.remove(attribute.start, attribute.end);
}
if (attribute.type === 'LetDirective') {
snippet_props.push(
attribute.name +
(attribute.expression
? `: ${state.str.original.substring(/** @type {number} */ (attribute.expression.start), /** @type {number} */ (attribute.expression.end))}`
: '')
);
// we just add to the queue to remove them after we found if we need to migrate or we bail
removal_queue.push(() => state.str.remove(attribute.start, attribute.end));
}
}
if (removal_queue.length > 0) {
for (let remove_let of removal_queue) {
remove_let();
}
}
if (node.type === 'SvelteFragment' && node.fragment.nodes.length > 0) {
// remove node itself, keep content
state.str.remove(node.start, node.fragment.nodes[0].start);
state.str.remove(node.fragment.nodes[node.fragment.nodes.length - 1].end, node.end);
}
const props = snippet_props.length > 0 ? `{ ${snippet_props.join(', ')} }` : '';
if (snippet_name === 'children' && node.type !== 'SvelteFragment') {
if (snippet_props.length === 0) return; // nothing to do
let inner_start = 0;
let inner_end = 0;
for (let i = 0; i < node.fragment.nodes.length; i++) {
const inner = node.fragment.nodes[i];
const is_empty_text = inner.type === 'Text' && !inner.data.trim();
if (
(inner.type === 'RegularElement' ||
inner.type === 'SvelteElement' ||
inner.type === 'Component' ||
inner.type === 'SvelteComponent' ||
inner.type === 'SlotElement' ||
inner.type === 'SvelteFragment') &&
inner.attributes.some((attr) => attr.type === 'Attribute' && attr.name === 'slot')
) {
if (inner_start && !inner_end) {
// End of default slot content
inner_end = inner.start;
}
} else if (!inner_start && !is_empty_text) {
// Start of default slot content
inner_start = inner.start;
} else if (inner_end && !is_empty_text) {
// There was default slot content before, then some named slot content, now some default slot content again.
// We're moving the last character back by one to avoid the closing {/snippet} tag inserted afterwards
// to come before the opening {#snippet} tag of the named slot.
state.str.update(inner_end - 1, inner_end, '');
state.str.prependLeft(inner_end - 1, state.str.original[inner_end - 1]);
state.str.move(inner.start, inner.end, inner_end - 1);
}
}
if (!inner_end) {
inner_end = node.fragment.nodes[node.fragment.nodes.length - 1].end;
}
state.str.appendLeft(
inner_start,
`{#snippet ${snippet_name}(${props})}\n${state.indent.repeat(path.length)}`
);
state.str.indent(state.indent, {
exclude: [
[0, inner_start],
[inner_end, state.str.original.length]
]
});
if (inner_end < node.fragment.nodes[node.fragment.nodes.length - 1].end) {
// Named slots coming afterwards
state.str.prependLeft(inner_end, `{/snippet}\n${state.indent.repeat(path.length)}`);
} else {
// No named slots coming afterwards
state.str.prependLeft(
inner_end,
`${state.indent.repeat(path.length)}{/snippet}\n${state.indent.repeat(path.length - 1)}`
);
}
} else {
// Named slot or `svelte:fragment`: wrap element itself in a snippet
state.str.prependLeft(
node.start,
`{#snippet ${snippet_name}(${props})}\n${state.indent.repeat(path.length - 2)}`
);
state.str.indent(state.indent, {
exclude: [
[0, node.start],
[node.end, state.str.original.length]
]
});
const str = `\n${state.indent.repeat(path.length - 2)}{/snippet}`;
if (node.type === 'SlotElement') {
state.str.appendRight(node.end, str);
} else {
state.str.appendLeft(node.end, str);
}
}
}
/**
* @param {VariableDeclarator} declarator
* @param {MagicString} str
* @param {SvelteNode[]} path
*/
function extract_type_and_comment(declarator, str, path) {
const parent = path.at(-1);
// Try to find jsdoc above the declaration
let comment_node = /** @type {Node} */ (parent)?.leadingComments?.at(-1);
const comment_start = /** @type {any} */ (comment_node)?.start;
const comment_end = /** @type {any} */ (comment_node)?.end;
let comment = comment_node && str.original.substring(comment_start, comment_end);
if (comment_node) {
str.update(comment_start, comment_end, '');
}
if (declarator.id.typeAnnotation) {
let start = declarator.id.typeAnnotation.start + 1; // skip the colon
while (str.original[start] === ' ') {
start++;
}
return { type: str.original.substring(start, declarator.id.typeAnnotation.end), comment };
}
let cleaned_comment = comment
?.split('\n')
.map((line) =>
line
.trim()
// replace `// ` for one liners
.replace(/^\/\/\s*/g, '')
// replace `\**` for the initial JSDoc
.replace(/^\/\*\*?\s*/g, '')
// migrate `*/` for the end of JSDoc
.replace(/\s*\*\/$/g, '')
// remove any initial `* ` to clean the comment
.replace(/^\*\s*/g, '')
)
.filter(Boolean);
const first_at_comment = cleaned_comment?.findIndex((line) => line.startsWith('@'));
comment = cleaned_comment
?.slice(0, first_at_comment !== -1 ? first_at_comment : cleaned_comment.length)
.join('\n');
// try to find a comment with a type annotation, hinting at jsdoc
if (parent?.type === 'ExportNamedDeclaration' && comment_node) {
const match = /@type {(.+)}/.exec(comment_node.value);
if (match) {
return { type: match[1], comment };
}
}
// try to infer it from the init
if (declarator.init?.type === 'Literal') {
const type = typeof declarator.init.value;
if (type === 'string' || type === 'number' || type === 'boolean') {
return { type, comment };
}
}
return { type: 'any', comment };
}
// Ensure modifiers are applied in the same order as Svelte 4
const modifier_order = [
'preventDefault',
'stopPropagation',
'stopImmediatePropagation',
'self',
'trusted',
'once'
];
/**
* @param {AST.RegularElement | AST.SvelteElement | AST.SvelteWindow | AST.SvelteDocument | AST.SvelteBody} element
* @param {State} state
*/
function handle_events(element, state) {
/** @type {Map<string, AST.OnDirective[]>} */
const handlers = new Map();
for (const attribute of element.attributes) {
if (attribute.type !== 'OnDirective') continue;
let name = `on${attribute.name}`;
if (attribute.modifiers.includes('capture')) {
name += 'capture';
}
const nodes = handlers.get(name) || [];
nodes.push(attribute);
handlers.set(name, nodes);
}
for (const [name, nodes] of handlers) {
const handlers = [];
let first = null;
for (const node of nodes) {
/** @type {string} */
let body;
if (node.expression) {
body = state.str.original.substring(
/** @type {number} */ (node.expression.start),
/** @type {number} */ (node.expression.end)
);
} else {
body = `${state.names.bubble}('${node.name}')`;
state.legacy_imports.add('createBubbler');
state.script_insertions.add(
`const ${state.names.bubble} = ${state.names.createBubbler}();`
);
}
const has_passive = node.modifiers.includes('passive');
const has_nonpassive = node.modifiers.includes('nonpassive');
const modifiers = modifier_order.filter((modifier) => node.modifiers.includes(modifier));
for (const modifier of modifiers) {
state.legacy_imports.add(modifier);
body = `${state.names[modifier]}(${body})`;
}
if (has_passive || has_nonpassive) {
const action = has_passive ? 'passive' : 'nonpassive';
state.legacy_imports.add(action);
state.str.overwrite(
node.start,
node.end,
`use:${state.names[action]}={['${node.name}', () => ${body}]}`
);
} else {
if (first) {
let start = node.start;
let end = node.end;
while (/[\s\n]/.test(state.str.original[start - 1])) start -= 1;
state.str.remove(start, end);
} else {
first = node;
}
handlers.push(body);
}
}
if (first) {
/** @type {string} */
let replacement;
if (handlers.length > 1) {
state.legacy_imports.add('handlers');
replacement = `${name}={${state.names.handlers}(${handlers.join(', ')})}`;
} else {
const handler = handlers[0];
replacement = handler === name ? `{${handler}}` : `${name}={${handler}}`;
}
state.str.overwrite(first.start, first.end, replacement);
}
}
}
/**
* Returns start and end of the node. If the start is preceeded with white-space-only before a line break,
* the start will be the start of the line.
* @param {string} source
* @param {LabeledStatement} node
*/
function get_node_range(source, node) {
const first_leading_comment = node.leadingComments?.[0];
const last_trailing_comment = node.trailingComments?.[node.trailingComments.length - 1];
// @ts-expect-error the type of `Comment` seems to be wrong...the node actually contains
// start and end but the type seems to only contain a `range` (which doesn't actually exists)
let start = /** @type {number} */ (first_leading_comment?.start ?? node.start);
// @ts-expect-error the type of `Comment` seems to be wrong...the node actually contains
// start and end but the type seems to only contain a `range` (which doesn't actually exists)
let end = /** @type {number} */ (last_trailing_comment?.end ?? node.end);
let idx = start;
while (source[idx - 1] !== '\n' && source[idx - 1] !== '\r') {
idx--;
if (source[idx] !== ' ' && source[idx] !== '\t') {
idx = start;
break;
}
}
start = idx;
return { start, end };
}
/**
* @param {Identifier} node
* @param {State} state
* @param {any[]} path
*/
function handle_identifier(node, state, path) {
const parent = path.at(-1);
if (parent?.type === 'MemberExpression' && parent.property === node) return;
if (state.analysis.uses_props && node.name !== '$$slots') {
if (node.name === '$$props' || node.name === '$$restProps') {
// not 100% correct for $$restProps but it'll do
state.str.update(
/** @type {number} */ (node.start),
/** @type {number} */ (node.end),
state.names.props
);
} else {
const binding = state.scope.get(node.name);
if (binding?.kind === 'bindable_prop') {
state.str.prependLeft(/** @type {number} */ (node.start), `${state.names.props}.`);
}
}
} else if (node.name === '$$restProps' && state.analysis.uses_rest_props) {
state.str.update(
/** @type {number} */ (node.start),
/** @type {number} */ (node.end),
state.names.rest
);
} else if (node.name === '$$slots' && state.analysis.uses_slots) {
if (parent?.type === 'MemberExpression') {
if (state.analysis.custom_element) return;
let name = parent.property.type === 'Literal' ? parent.property.value : parent.property.name;
let slot_name = name;
const existing_prop = state.props.find((prop) => prop.slot_name === name);
if (existing_prop) {
name = existing_prop.local;
} else if (name !== 'default') {
let new_name = state.scope.generate(name);
if (new_name !== name) {
throw new Error(
'This migration would change the name of a slot making the component unusable'
);
}
}
name = name === 'default' ? 'children' : name;
if (!existing_prop) {
state.props.push({
local: name,
exported: name,
init: '',
bindable: false,
optional: true,
slot_name,
// if it's the first time we encounter this slot
// we start with any and delegate to when the slot
// is actually rendered (it might not happen in that case)
// any is still a safe bet
type: `import('svelte').Snippet<[any]>`,
needs_refine_type: true
});
}
state.str.update(
/** @type {number} */ (node.start),
parent.property.start,
state.analysis.uses_props ? `${state.names.props}.` : ''
);
state.str.update(parent.property.start, parent.end, name);
}
// else passed as identifier, we don't know what to do here, so let it error
} else if (
parent?.type === 'TSInterfaceDeclaration' ||
parent?.type === 'TSTypeAliasDeclaration'
) {
const members =
parent.type === 'TSInterfaceDeclaration' ? parent.body.body : parent.typeAnnotation?.members;
if (Array.isArray(members)) {
if (node.name === '$$Props') {
for (const member of members) {
const prop = state.props.find((prop) => prop.exported === member.key.name);
const type = state.str.original.substring(
member.typeAnnotation.typeAnnotation.start,
member.typeAnnotation.typeAnnotation.end
);
let comment;
const comment_node = member.leadingComments?.at(-1);
if (comment_node?.type === 'Block') {
comment = state.str.original.substring(comment_node.start, comment_node.end);
}
if (prop) {
prop.type = type;
prop.optional = member.optional;
prop.comment = comment ?? prop.comment;
} else {
state.props.push({
local: member.key.name,
exported: member.key.name,
init: '',
bindable: false,
optional: member.optional,
type,
comment,
type_only: true
});
}
}
state.str.remove(parent.start, parent.end);
}
}
}
}
/** @param {string} content */
function guess_indent(content) {
const lines = content.split('\n');
const tabbed = lines.filter((line) => /^\t+/.test(line));
const spaced = lines.filter((line) => /^ {2,}/.test(line));
if (tabbed.length === 0 && spaced.length === 0) {
return '\t';
}
// More lines tabbed than spaced? Assume tabs, and
// default to tabs in the case of a tie (or nothing
// to go on)
if (tabbed.length >= spaced.length) {
return '\t';
}
// Otherwise, we need to guess the multiple
const min = spaced.reduce((previous, current) => {
const count = /^ +/.exec(current)?.[0].length ?? 0;
return Math.min(count, previous);
}, Infinity);
return ' '.repeat(min);
}
|