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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_warnings } from '../warnings.js';
import { extract_identifiers } from '../utils/ast.js';
/**
* Does a best-effort migration of Svelte code towards using runes, event attributes and render tags.
* @param {string} source
* @returns {string}
*/
export function migrate(source) {
try {
reset_warnings({ 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: 0,
has_props_rune: false,
props_name: analysis.root.unique('props').name,
rest_props_name: analysis.root.unique('rest').name,
end: parsed.end
};
if (parsed.instance) {
walk(parsed.instance.content, state, instance_script);
}
state = { ...state, scope: analysis.template.scope };
walk(parsed.fragment, state, template);
if (state.props.length > 0 || analysis.uses_rest_props || analysis.uses_props) {
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 += ` = ${prop.init}`;
}
return prop_str;
})
.join(', ');
if (analysis.uses_rest_props) {
props += `, ...${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 props_declaration = `let { ${props} } = $props();`;
if (parsed.instance) {
if (state.props_insertion_point === 0) {
// no regular props found, but render tags or events to forward found, $props() will be first in the script tag
str.appendRight(
/** @type {number} */ (parsed.instance.content.start),
`\n${indent}${props_declaration}`
);
} else {
str.appendRight(state.props_insertion_point, props_declaration);
}
} else {
str.prepend(`<script>\n${indent}${props_declaration}\n</script>`);
}
}
}
return str.toString();
} catch (e) {
console.error('Error while migrating Svelte code');
throw e;
}
}
/**
* @typedef {{
* scope: import('../phases/scope.js').Scope;
* str: MagicString;
* analysis: import('../phases/types.js').ComponentAnalysis;
* indent: string;
* props: Array<{ local: string; exported: string; init: string; bindable: boolean }>;
* props_insertion_point: number;
* has_props_rune: boolean;
* props_name: string;
* rest_props_name: string;
* end: number;
* }} State
*/
/** @type {import('zimmerframe').Visitors<import('../types/template.js').SvelteNode, State>} */
const instance_script = {
Identifier(node, { state }) {
handle_identifier(node, state);
},
VariableDeclaration(node, { state, path }) {
if (state.scope !== state.analysis.instance.scope) {
return;
}
let nr_of_props = 0;
for (const declarator of node.declarations) {
if (state.analysis.runes) {
if (get_rune(declarator.init, state.scope) === '$props') {
state.props_insertion_point = /** @type {number} */ (declarator.id.start) + 1;
state.has_props_rune = true;
}
continue;
}
const bindings = state.scope.get_bindings(declarator);
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
// 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));
// }
// }
continue;
}
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)
)
: '',
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);
}
state.str.update(start, end, '');
}
},
LabeledStatement(node, { path, state }) {
if (state.analysis.runes) return;
if (path.length > 1) return;
if (node.label.name !== '$') return;
if (
node.body.type === 'ExpressionStatement' &&
node.body.expression.type === 'AssignmentExpression'
) {
const ids = extract_identifiers(node.body.expression.left);
const reassigned_ids = ids.filter((id) => state.scope.get(id.name)?.reassigned);
if (reassigned_ids.length === 0) {
// $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 id of reassigned_ids) {
const binding = state.scope.get(id.name);
if (binding?.node === id) {
// implicitly-declared variable which we need to make explicit
state.str.prependLeft(
/** @type {number} */ (node.start),
`let ${id.name}${binding.kind === 'state' ? ' = $state()' : ''};\n${state.indent}`
);
}
}
}
}
const is_block_stmt = node.body.type === 'BlockStatement';
const start_end = /** @type {number} */ (node.body.start);
// $effect.pre, to be precise, but we gloss over that
// TODO try to find out if we can use $derived.by instead?
// TODO SSR mode variant needed
if (is_block_stmt) {
state.str.update(/** @type {number} */ (node.start), start_end + 1, '$effect(() => {');
const end = /** @type {number} */ (node.body.end);
state.str.update(end - 1, end, '});');
} else {
state.str.update(
/** @type {number} */ (node.start),
start_end,
`$effect(() => {\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);
},
OnDirective(node, { state, path }) {
const parent = path.at(-1);
if (
parent?.type === 'SvelteSelf' ||
parent?.type === 'SvelteComponent' ||
parent?.type === 'Component'
) {
return;
}
if (node.expression) {
// remove : from on:click
state.str.update(node.start, node.start + 3, 'on');
} else {
// turn on:click into a prop
// Check if prop already set, could happen when on:click on different elements
// TODO what to do when this results in a variable name clash?
if (!state.props.some((prop) => prop.local === node.name)) {
state.props.push({
local: node.name,
exported: node.name,
init: '',
bindable: false
});
}
state.str.update(node.start, node.end, `{${node.name}}`);
}
},
SlotElement(node, { state }) {
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 = /** @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
});
if (node.fragment.nodes.length > 0) {
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})}`);
}
}
};
/**
* @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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