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chore: simplify parser (#18077)

Browse Source 
small tidy-up spurred by #17954 — rather than try-catching every
`parse_expression_at` call and passing the error to
`parser.acorn_error`, we can handle the error locally and get rid of
that method

### Before submitting the PR, please make sure you do the following

- [ ] It's really useful if your PR references an issue where it is
discussed ahead of time. In many cases, features are absent for a
reason. For large changes, please create an RFC:
https://github.com/sveltejs/rfcs
- [x] Prefix your PR title with `feat:`, `fix:`, `chore:`, or `docs:`.
- [x] This message body should clearly illustrate what problems it
solves.
- [ ] Ideally, include a test that fails without this PR but passes with
it.
- [ ] If this PR changes code within `packages/svelte/src`, add a
changeset (`npx changeset`).

### Tests and linting

- [x] Run the tests with `pnpm test` and lint the project with `pnpm
lint`

---------

Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>
pull/18036/head
Rich Harris 2 weeks ago committed by GitHub
parent 8966601dcd
commit 6b653b8d17
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
5 changed files with 69 additions and 72 deletions
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66
packages/svelte/src/compiler/phases/1-parse/acorn.js
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@ -4,8 +4,10 @@
import * as acorn from 'acorn';
import { walk } from 'zimmerframe';
import { tsPlugin } from '@sveltejs/acorn-typescript';
import * as e from '../../errors.js';
const ParserWithTS = acorn.Parser.extend(tsPlugin());
const JSParser = acorn.Parser;
const TSParser = JSParser.extend(tsPlugin());
/**
* @typedef {Comment & {
@ -21,15 +23,15 @@ const ParserWithTS = acorn.Parser.extend(tsPlugin());
* @param {boolean} [is_script]
*/
export function parse(source, comments, typescript, is_script) {
const parser = typescript ? ParserWithTS : acorn.Parser;
const acorn = typescript ? TSParser : JSParser;
const { onComment, add_comments } = get_comment_handlers(
source,
/** @type {CommentWithLocation[]} */ (comments)
);
// @ts-ignore
const parse_statement = parser.prototype.parseStatement;
// @ts-expect-error
const parse_statement = acorn.prototype.parseStatement;
// If we're dealing with a <script> then it might contain an export
// for something that doesn't exist directly inside but is inside the
@ -37,7 +39,7 @@ export function parse(source, comments, typescript, is_script) {
// an error in these cases
if (is_script) {
// @ts-ignore
parser.prototype.parseStatement = function (...args) {
acorn.prototype.parseStatement = function (...args) {
const v = parse_statement.call(this, ...args);
// @ts-ignore
this.undefinedExports = {};
@ -45,25 +47,27 @@ export function parse(source, comments, typescript, is_script) {
};
}
let ast;
try {
ast = parser.parse(source, {
const ast = acorn.parse(source, {
onComment,
sourceType: 'module',
ecmaVersion: 16,
locations: true
});
add_comments(ast);
return /** @type {Program} */ (ast);
} catch (err) {
// TODO the `return` in necessary for TS<7 due to a bug; otherwise
// the `finally` block is regarded as unreachable
return handle_parse_error(err);
} finally {
if (is_script) {
// @ts-ignore
parser.prototype.parseStatement = parse_statement;
// @ts-expect-error
acorn.prototype.parseStatement = parse_statement;
}
}
add_comments(ast);
return /** @type {Program} */ (ast);
}
/**
@ -73,21 +77,35 @@ export function parse(source, comments, typescript, is_script) {
* @returns {acorn.Expression & { leadingComments?: CommentWithLocation[]; trailingComments?: CommentWithLocation[]; }}
*/
export function parse_expression_at(parser, source, index) {
const _ = parser.ts ? ParserWithTS : acorn.Parser;
const acorn = parser.ts ? TSParser : JSParser;
const { onComment, add_comments } = get_comment_handlers(source, parser.root.comments, index);
const ast = _.parseExpressionAt(source, index, {
onComment,
sourceType: 'module',
ecmaVersion: 16,
locations: true,
preserveParens: true
});
try {
const ast = acorn.parseExpressionAt(source, index, {
onComment,
sourceType: 'module',
ecmaVersion: 16,
locations: true,
preserveParens: true
});
add_comments(ast);
add_comments(ast);
return ast;
return ast;
} catch (e) {
handle_parse_error(e);
}
}
const regex_position_indicator = / \(\d+:\d+\)$/;
/**
* @param {any} err
* @returns {never}
*/
function handle_parse_error(err) {
e.js_parse_error(err.pos, err.message.replace(regex_position_indicator, ''));
}
/**

10
packages/svelte/src/compiler/phases/1-parse/index.js
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@ -11,8 +11,6 @@ import { is_reserved } from '../../../utils.js';
import { disallow_children } from '../2-analyze/visitors/shared/special-element.js';
import * as state from '../../state.js';
const regex_position_indicator = / \(\d+:\d+\)$/;
/** @param {number} cc */
function is_whitespace(cc) {
// fast path for common whitespace
@ -175,14 +173,6 @@ export class Parser {
return this.stack[this.stack.length - 1];
}
/**
* @param {any} err
* @returns {never}
*/
acorn_error(err) {
e.js_parse_error(err.pos, err.message.replace(regex_position_indicator, ''));
}
/**
* @param {string} str
* @param {boolean} required

54
packages/svelte/src/compiler/phases/1-parse/read/context.js
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@ -35,36 +35,32 @@ export default function read_pattern(parser) {
const pattern_string = parser.template.slice(start, i);
try {
// the length of the `space_with_newline` has to be start - 1
// because we added a `(` in front of the pattern_string,
// which shifted the entire string to right by 1
// so we offset it by removing 1 character in the `space_with_newline`
// to achieve that, we remove the 1st space encountered,
// so it will not affect the `column` of the node
let space_with_newline = parser.template
.slice(0, start)
.replace(regex_not_newline_characters, ' ');
const first_space = space_with_newline.indexOf(' ');
space_with_newline =
space_with_newline.slice(0, first_space) + space_with_newline.slice(first_space + 1);
/** @type {any} */
let expression = remove_parens(
parse_expression_at(parser, `${space_with_newline}(${pattern_string} = 1)`, start - 1)
);
expression = expression.left;
expression.typeAnnotation = read_type_annotation(parser);
if (expression.typeAnnotation) {
expression.end = expression.typeAnnotation.end;
}
return expression;
} catch (error) {
parser.acorn_error(error);
// the length of the `space_with_newline` has to be start - 1
// because we added a `(` in front of the pattern_string,
// which shifted the entire string to right by 1
// so we offset it by removing 1 character in the `space_with_newline`
// to achieve that, we remove the 1st space encountered,
// so it will not affect the `column` of the node
let space_with_newline = parser.template
.slice(0, start)
.replace(regex_not_newline_characters, ' ');
const first_space = space_with_newline.indexOf(' ');
space_with_newline =
space_with_newline.slice(0, first_space) + space_with_newline.slice(first_space + 1);
/** @type {any} */
let expression = remove_parens(
parse_expression_at(parser, `${space_with_newline}(${pattern_string} = 1)`, start - 1)
);
expression = expression.left;
expression.typeAnnotation = read_type_annotation(parser);
if (expression.typeAnnotation) {
expression.end = expression.typeAnnotation.end;
}
return expression;
}
/**

2
packages/svelte/src/compiler/phases/1-parse/read/expression.js
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@ -54,6 +54,6 @@ export default function read_expression(parser, opening_token, disallow_loose) {
}
}
parser.acorn_error(err);
throw err;
}
}

9
packages/svelte/src/compiler/phases/1-parse/read/script.js
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@ -31,14 +31,7 @@ export function read_script(parser, start, attributes) {
parser.template.slice(0, script_start).replace(regex_not_newline_characters, ' ') + data;
parser.read(regex_starts_with_closing_script_tag);
/** @type {Program} */
let ast;
try {
ast = acorn.parse(source, parser.root.comments, parser.ts, true);
} catch (err) {
parser.acorn_error(err);
}
const ast = acorn.parse(source, parser.root.comments, parser.ts, true);
ast.start = script_start;

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