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5x 5x 5x 5x 5x 5x 5x 5x 5x 5x 6x 1x 1x 1x 1x 1x 1x 1x 1x 1x 6x 13x 4x 4x 4x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 4x 4x 4x 3x 2x 3x 1x 1x 4x 1x 1x 4x 4x 4x 13x 24x 2x 2x 2x 2x 2x 13x 13x 13x 13x 13x 13x 2x 2x 2x 2x 2x 48x 48x 48x 1x 1x 1x 1x 1x 1x 48x 2x 2x 10x 10x 10x 10x 10x 10x 10x 2x 2x 8x 8x 8x 8x 10x 5x 5x 3x 3x 3x 9x 9x 3x 3x 3x 3x | import MagicString from 'magic-string';
import { walk } from 'zimmerframe';
import { parse } from '../phases/1-parse/index.js';
import { analyze_component } from '../phases/2-analyze/index.js';
import { validate_component_options } from '../validate-options.js';
import { get_rune } from '../phases/scope.js';
import { reset } from '../state.js';
import { extract_identifiers } from '../utils/ast.js';
import { regex_is_valid_identifier } from '../phases/patterns.js';
import { migrate_svelte_ignore } from '../utils/extract_svelte_ignore.js';
/**
* 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
* @returns {{ code: string; }}
*/
export function migrate(source) {
try {
reset(source, { filename: 'migrate.svelte' });
let parsed = parse(source);
const { customElement: customElementOptions, ...parsed_options } = parsed.options || {};
/** @type {import('#compiler').ValidatedCompileOptions} */
const combined_options = {
...validate_component_options({}, ''),
...parsed_options,
customElementOptions
};
const str = new MagicString(source);
const analysis = analyze_component(parsed, source, combined_options);
const indent = guess_indent(source);
/** @type {State} */
let state = {
scope: analysis.instance.scope,
analysis,
str,
indent,
props: [],
props_insertion_point: parsed.instance?.content.start ?? 0,
has_props_rune: false,
props_name: analysis.root.unique('props').name,
rest_props_name: analysis.root.unique('rest').name,
end: source.length,
run_name: analysis.root.unique('run').name,
needs_run: false
};
if (parsed.instance) {
walk(parsed.instance.content, state, instance_script);
}
state = { ...state, scope: analysis.template.scope };
walk(parsed.fragment, state, template);
const run_import = `import { run${state.run_name === 'run' ? '' : `as ${state.run_name}`} } from 'svelte/legacy';`;
let added_legacy_import = false;
if (state.props.length > 0 || analysis.uses_rest_props || analysis.uses_props) {
const has_many_props = state.props.length > 3;
const props_separator = has_many_props ? `\n${indent}${indent}` : ' ';
let props = '';
if (analysis.uses_props) {
props = `...${state.props_name}`;
} else {
props = state.props
.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 += `,${props_separator}...${state.rest_props_name}`;
}
}
if (state.has_props_rune) {
// some render tags or forwarded event attributes to add
str.appendRight(state.props_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) {
if (analysis.uses_props || analysis.uses_rest_props) {
type = `interface ${type_name} { [key: string]: any }`;
} else {
type = `interface ${type_name} {${props_separator}${state.props
.map((prop) => {
return `${prop.exported}${prop.optional ? '?' : ''}: ${prop.type}`;
})
.join(`,${props_separator}`)}${has_many_props ? `\n${indent}` : ' '}}`;
}
} else {
if (analysis.uses_props || analysis.uses_rest_props) {
type = `{Record<string, any>}`;
} else {
type = `{${state.props
.map((prop) => {
return `${prop.exported}${prop.optional ? '?' : ''}: ${prop.type}`;
})
.join(`, `)}}`;
}
}
let props_declaration = `let {${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}` : ''} = $props();`;
} else {
props_declaration = `/** @type {${type}} */\n${indent}${props_declaration}`;
props_declaration = `${props_declaration} = $props();`;
}
if (parsed.instance) {
props_declaration = `\n${indent}${props_declaration}`;
str.appendRight(state.props_insertion_point, props_declaration);
} else {
const imports = state.needs_run ? `${indent}${run_import}\n` : '';
str.prepend(`<script>\n${imports}${indent}${props_declaration}\n</script>\n\n`);
added_legacy_import = true;
}
}
}
if (state.needs_run && !added_legacy_import) {
if (parsed.instance) {
str.appendRight(
/** @type {number} */ (parsed.instance.content.start),
`\n${indent}${run_import}\n`
);
} else {
str.prepend(`<script>\n${indent}${run_import}\n</script>\n\n`);
}
}
return { code: str.toString() };
} catch (e) {
// eslint-disable-next-line no-console
console.error('Error while migrating Svelte code');
throw e;
}
}
/**
* @typedef {{
* scope: import('../phases/scope.js').Scope;
* str: MagicString;
* analysis: import('../phases/types.js').ComponentAnalysis;
* indent: string;
* props: Array<{ local: string; exported: string; init: string; bindable: boolean; optional: boolean; type: string }>;
* props_insertion_point: number;
* has_props_rune: boolean;
* props_name: string;
* rest_props_name: string;
* end: number;
* run_name: string;
* needs_run: boolean;
* }} State
*/
/** @type {import('zimmerframe').Visitors<import('../types/template.js').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 }) {
handle_identifier(node, state);
},
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 }) {
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
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) {
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 binding = /** @type {import('#compiler').Binding} */ (
state.scope.get(declarator.id.name)
);
if (
state.analysis.uses_props &&
(declarator.init || binding.mutated || binding.reassigned)
) {
throw new Error(
'$$props is used together with named props in a way that cannot be automatically migrated.'
);
}
state.props.push({
local: declarator.id.name,
exported: binding.prop_alias ? binding.prop_alias : declarator.id.name,
init: declarator.init
? state.str.original.substring(
/** @type {number} */ (declarator.init.start),
/** @type {number} */ (declarator.init.end)
)
: '',
optional: !!declarator.init,
type: extract_type(declarator, state.str, path),
bindable: binding.mutated || binding.reassigned
});
state.props_insertion_point = /** @type {number} */ (declarator.end);
state.str.update(
/** @type {number} */ (declarator.start),
/** @type {number} */ (declarator.end),
''
);
continue;
}
// state
if (declarator.init) {
state.str.prependLeft(/** @type {number} */ (declarator.init.start), '$state(');
state.str.appendRight(/** @type {number} */ (declarator.init.end), ')');
} else {
state.str.prependLeft(/** @type {number} */ (declarator.id.end), ' = $state()');
}
}
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;
next();
if (
node.body.type === 'ExpressionStatement' &&
node.body.expression.type === 'AssignmentExpression'
) {
const ids = extract_identifiers(node.body.expression.left);
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')) {
// $derived
state.str.update(
/** @type {number} */ (node.start),
/** @type {number} */ (node.body.expression.start),
'let '
);
state.str.prependLeft(
/** @type {number} */ (node.body.expression.right.start),
'$derived('
);
state.str.update(
/** @type {number} */ (node.body.expression.right.end),
/** @type {number} */ (node.end),
');'
);
return;
} else {
for (const binding of reassigned_bindings) {
if (binding && ids.includes(binding.node)) {
// implicitly-declared variable which we need to make explicit
state.str.prependLeft(
/** @type {number} */ (node.start),
`let ${binding.node.name}${binding.kind === 'state' ? ' = $state()' : ''};\n${state.indent}`
);
}
}
}
}
state.needs_run = true;
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.run_name}(() => {`
);
const end = /** @type {number} */ (node.body.end);
state.str.update(end - 1, end, '});');
} else {
state.str.update(
/** @type {number} */ (node.start),
start_end,
`${state.run_name}(() => {\n${state.indent}`
);
state.str.indent(state.indent, {
exclude: [
[0, /** @type {number} */ (node.body.start)],
[/** @type {number} */ (node.body.end), state.end]
]
});
state.str.appendRight(/** @type {number} */ (node.end), `\n${state.indent}});`);
}
}
};
/** @type {import('zimmerframe').Visitors<import('../types/template.js').SvelteNode, State>} */
const template = {
Identifier(node, { state }) {
handle_identifier(node, state);
},
RegularElement(node, { state, next }) {
handle_events(node, state);
next();
},
SvelteElement(node, { state, next }) {
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();
},
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, next }) {
let name = 'children';
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 === 'name') {
name = state.scope.generate(/** @type {any} */ (attr.value)[0].data);
} else {
const value =
attr.value !== true
? state.str.original.substring(
attr.value[0].start,
attr.value[attr.value.length - 1].end
)
: 'true';
slot_props += value === attr.name ? `${value}, ` : `${attr.name}: ${value}, `;
}
}
}
slot_props += '}';
if (slot_props === '{ }') {
slot_props = '';
}
state.props.push({
local: name,
exported: name,
init: '',
bindable: false,
optional: true,
type: `import('svelte').${slot_props ? 'Snippet<[any]>' : 'Snippet'}`
});
if (node.fragment.nodes.length > 0) {
next();
state.str.update(
node.start,
node.fragment.nodes[0].start,
`{#if ${name}}{@render ${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 ${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 {import('estree').VariableDeclarator} declarator
* @param {MagicString} str
* @param {import('#compiler').SvelteNode[]} path
*/
function extract_type(declarator, str, path) {
if (declarator.id.typeAnnotation) {
let start = declarator.id.typeAnnotation.start + 1; // skip the colon
while (str.original[start] === ' ') {
start++;
}
return str.original.substring(start, declarator.id.typeAnnotation.end);
}
// try to find a comment with a type annotation, hinting at jsdoc
const parent = path.at(-1);
if (parent?.type === 'ExportNamedDeclaration' && parent.leadingComments) {
const last = parent.leadingComments[parent.leadingComments.length - 1];
if (last.type === 'Block') {
const match = /@type {([^}]+)}/.exec(last.value);
if (match) {
str.update(/** @type {any} */ (last).start, /** @type {any} */ (last).end, '');
return match[1];
}
}
}
// 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;
}
}
return 'any';
}
/**
* @param {import('#compiler').RegularElement | import('#compiler').SvelteElement | import('#compiler').SvelteWindow | import('#compiler').SvelteDocument | import('#compiler').SvelteBody} node
* @param {State} state
*/
function handle_events(node, state) {
/** @type {Map<string, import('#compiler').OnDirective[]>} */
const handlers = new Map();
for (const attribute of node.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) {
// turn on:click into a prop
let exported = name;
if (!regex_is_valid_identifier.test(name)) {
exported = `'${exported}'`;
}
// Check if prop already set, could happen when on:click on different elements
let local = state.props.find((prop) => prop.exported === exported)?.local;
const last = nodes[nodes.length - 1];
const payload_name =
last.expression?.type === 'ArrowFunctionExpression' &&
last.expression.params[0]?.type === 'Identifier'
? last.expression.params[0].name
: generate_event_name(last, state);
let prepend = '';
for (let i = 0; i < nodes.length - 1; i += 1) {
const node = nodes[i];
if (node.expression) {
let body = '';
if (node.expression.type === 'ArrowFunctionExpression') {
body = state.str.original.substring(
/** @type {number} */ (node.expression.body.start),
/** @type {number} */ (node.expression.body.end)
);
} else {
body = `${state.str.original.substring(
/** @type {number} */ (node.expression.start),
/** @type {number} */ (node.expression.end)
)}();`;
}
// TODO check how many indents needed
for (const modifier of node.modifiers) {
if (modifier === 'stopPropagation') {
body = `\n${state.indent}${payload_name}.stopPropagation();\n${body}`;
} else if (modifier === 'preventDefault') {
body = `\n${state.indent}${payload_name}.preventDefault();\n${body}`;
} else if (modifier === 'stopImmediatePropagation') {
body = `\n${state.indent}${payload_name}.stopImmediatePropagation();\n${body}`;
} else {
body = `\n${state.indent}// @migration-task: incorporate ${modifier} modifier\n${body}`;
}
}
prepend += `\n${state.indent}${body}\n`;
} else {
if (!local) {
local = state.scope.generate(`on${node.name}`);
state.props.push({
local,
exported,
init: '',
bindable: false,
optional: true,
type: '(event: any) => void'
});
}
prepend += `\n${state.indent}${local}?.(${payload_name});\n`;
}
state.str.remove(node.start, node.end);
}
if (last.expression) {
// remove : from on:click
state.str.remove(last.start + 2, last.start + 3);
// remove modifiers
if (last.modifiers.length > 0) {
state.str.remove(
last.start + last.name.length + 3,
state.str.original.indexOf('=', last.start)
);
}
if (last.modifiers.includes('capture')) {
state.str.appendRight(last.start + last.name.length + 3, 'capture');
}
for (const modifier of last.modifiers) {
if (modifier === 'stopPropagation') {
prepend += `\n${state.indent}${payload_name}.stopPropagation();\n`;
} else if (modifier === 'preventDefault') {
prepend += `\n${state.indent}${payload_name}.preventDefault();\n`;
} else if (modifier === 'stopImmediatePropagation') {
prepend += `\n${state.indent}${payload_name}.stopImmediatePropagation();\n`;
} else if (modifier !== 'capture') {
prepend += `\n${state.indent}// @migration-task: incorporate ${modifier} modifier\n`;
}
}
if (prepend) {
let pos = last.expression.start;
if (last.expression.type === 'ArrowFunctionExpression') {
pos = last.expression.body.start;
if (
last.expression.params.length > 0 &&
last.expression.params[0].type !== 'Identifier'
) {
const start = /** @type {number} */ (last.expression.params[0].start);
const end = /** @type {number} */ (last.expression.params[0].end);
// replace event payload with generated one that others use,
// then destructure generated payload param into what the user wrote
state.str.overwrite(start, end, payload_name);
prepend = `let ${state.str.original.substring(
start,
end
)} = ${payload_name};\n${prepend}`;
} else if (last.expression.params.length === 0) {
// add generated payload param to arrow function
const pos = state.str.original.lastIndexOf(')', last.expression.body.start);
state.str.prependLeft(pos, payload_name);
}
const needs_curlies = last.expression.body.type !== 'BlockStatement';
state.str.prependRight(
/** @type {number} */ (pos) + (needs_curlies ? 0 : 1),
`${needs_curlies ? '{' : ''}${prepend}${state.indent}`
);
state.str.appendRight(
/** @type {number} */ (last.expression.body.end) - (needs_curlies ? 0 : 1),
`\n${needs_curlies ? '}' : ''}`
);
} else {
state.str.update(
/** @type {number} */ (last.expression.start),
/** @type {number} */ (last.expression.end),
`(${payload_name}) => {${prepend}\n${state.indent}${state.str.original.substring(
/** @type {number} */ (last.expression.start),
/** @type {number} */ (last.expression.end)
)}?.(${payload_name});\n}`
);
}
}
} else {
// turn on:click into a prop
// Check if prop already set, could happen when on:click on different elements
if (!local) {
local = state.scope.generate(`on${last.name}`);
state.props.push({
local,
exported,
init: '',
bindable: false,
optional: true,
type: '(event: any) => void'
});
}
let replacement = '';
if (!prepend) {
if (exported === local) {
replacement = `{${name}}`;
} else {
replacement = `${name}={${local}}`;
}
} else {
replacement = `${name}={(${payload_name}) => {${prepend}\n${state.indent}${local}?.(${payload_name});\n}}`;
}
state.str.update(last.start, last.end, replacement);
}
}
}
/**
* @param {import('#compiler').OnDirective} last
* @param {State} state
*/
function generate_event_name(last, state) {
const scope =
(last.expression && state.analysis.template.scopes.get(last.expression)) || state.scope;
let name = 'event';
if (!scope.get(name)) return name;
let i = 1;
while (scope.get(`${name}${i}`)) i += 1;
return `${name}${i}`;
}
/**
* @param {import('estree').Identifier} node
* @param {State} state
*/
function handle_identifier(node, state) {
if (state.analysis.uses_props) {
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.props_name
);
} else {
const binding = state.scope.get(node.name);
if (binding?.kind === 'bindable_prop') {
state.str.prependLeft(/** @type {number} */ (node.start), `${state.props_name}.`);
}
}
} else if (node.name === '$$restProps' && state.analysis.uses_rest_props) {
state.str.update(
/** @type {number} */ (node.start),
/** @type {number} */ (node.end),
state.rest_props_name
);
}
}
/** @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);
}
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