Introduce parser error codes #13033

sosukesuzuki · 2021-03-21T16:49:52Z

Q	A
Fixed Issues?	Fixes #13007
Patch: Bug Fix?	Maybe yes
Minor: New Feature?	Maybe no
Tests Added + Pass?	Yes
License	MIT

If you have an idea for better interface, please comment!

babel-bot · 2021-03-21T16:52:11Z

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nicolo-ribaudo · 2021-03-22T15:46:05Z

packages/babel-parser/src/parser/error-message.js

+// These errors have a different error code than the key
+export const SourceTypeModuleErrorMessages: ErrorTemplates = Object.freeze({
+  ImportMetaOutsideModule: {
+    code: "BABEL_PARSER_SOURCETYPE_MODULE_REQUIRED",


Good catch!

nicolo-ribaudo · 2021-03-22T15:49:15Z

packages/babel-parser/src/parser/error-message.js

+  AccessorIsGenerator: {
+    code: "AccessorIsGenerator",
+    template: "A %0ter cannot be a generator",
+  },


It's just a stylistic preference, but I don't really like that we have to repeat so much boilerplate (duplicating every code, and the code/template keys for every message).

Maybe we could do something like this?

export const ErrorMessages = makeErrorTemplates({ AccessorIsGenerator: "A %0ter cannot be a generator", ... }); export function makeErrorTemplates(messages) { Object.keys(messages).forEach(code => { messages[code] = { code, template: messages[code] }; }); }

it's a one-time cost only paid when importing @babel/parser.

nicolo-ribaudo · 2021-03-23T13:56:50Z

packages/babel-parser/src/parser/error-message.js

 /* eslint sort-keys: "error" */

 /**
 * @module parser/error-message
 */

 // The Errors key follows https://cs.chromium.org/chromium/src/v8/src/common/message-template.h unless it does not exist
-export const ErrorMessages = Object.freeze({
+export const ErrorMessages: ErrorTemplates = makeErrorTemplates({


Nit: This is probably not needed anymore, since it's inferred from makeErrorTemplates's return type.

Suggested change

export const ErrorMessages: ErrorTemplates = makeErrorTemplates({

export const ErrorMessages = makeErrorTemplates({

nicolo-ribaudo · 2021-03-23T14:00:44Z

packages/babel-parser/src/parser/util.js

+    throw this.raise(pos != null ? pos : this.state.start, {
+      code: "UnexpectedToken",
+      template: messageOrType,
+    });


I think here it would be better if the signature was

unexpected(pos: ?number, messageOrType: TokenType | ErrorTemplate)

and if we get an error template we use the correct code rather than UnexpectedToken.

existentialism

👍

nicolo-ribaudo · 2021-03-25T16:00:13Z

Should this wait for a minor?

JLHwung · 2021-03-25T17:41:52Z

Note that the code of parsing error is now a contract between Babel and users. We may want to review our current error code to see if there is any typo / wording inconsistency. Then it should be good to land.

JLHwung · 2021-03-25T18:00:05Z

packages/babel-parser/src/plugins/jsx/index.js

-                `Unexpected token \`${char}\`. Did you mean \`${htmlEntity}\` or \`{'${char}'}\`?`,
-              );
+              this.raise(this.state.pos, {
+                code: "UnexpectedToken",


Should we prefix error code with BABEL_PARSER like we did in BABEL_PARSER_SOURCETYPE_MODULE_REQUIRED? Should we use SNAKE_CASE instead?

Or maybe we could always set code to BABEL_PARSER_ERROR, and add a new property (like errorCode, or parserError) using these new codes we are introducing.

I prefer a prefixed error code but don't have a strong opinion. The Node.js recommends error.code to be the identifier of the error. Conventionally they use SNAKE_CASE. I don't have strong opinion between camelCase and SNAKE_CASE, as long as we have consensus.

https://nodejs.org/api/errors.html#errors_error_code

I would like to maintain the same stability policy as Node.js: The error.code thrown from @babel/parser is considered stable: It will only be changed in a major release, but not for error.message which we will keep polishing between patches/minors.

Yeah but I wonder how useful these specific error messages are.

Except for a few (and they already have specific codes), I think often I would want do do something like this:

try { somethingThatCallsBabel(); } catch (e) { if (e.code === "BABEL_PARSER_ERROR") { console.warn("The file contains invalid syntax!"); } else if (e.code === "BABEL_PARSER_MISSING_PLUGIN") { console.warn("You might want to enable a parser plugin!"); } else if (e.code === "BABEL_PARSER_SOURCETYPE_MODULE_REQUIRED") { console.warn("You are parsing a module as a script!"); } else if (e.code === "ENOENT") { console.warn("You are trying to parse a non-existing file!"); } else { throw e; } }

Imho the specific syntax error is a detail at a deeper leverl.

I would like to maintain the same stability policy as Node.js: The error.code thrown from @babel/parser is considered stable

+1

The new example looks good to me. In that case we may consider place current detailed error code to syntaxError or reasonCode.

I think BABEL_PARSER_ERROR is too general, maybe BABEL_PARSER_INVALID_SYNTAX or BABEL_PARSER_SYNTAX_ERROR?

Yeah I like that (I don't have a preference about the exact names).

I would like to maintain the same stability policy as Node.js: The error.code thrown from @babel/parser is considered stable

👍

To summarize, the interface will look like this?:

{ code: "BABEL_PARSER_SYNTAX_ERROR", reasonCode: "ArgumentsInClass", message: "'arguments' is only allowed in functions and class methods" }

Dismissing my approval for now, since there will be more changes.

sosukesuzuki · 2021-03-26T08:01:05Z

Also, code and reasonCode are now contract between Babel and users so we should introduce testing for it.

sosukesuzuki · 2021-03-26T14:46:18Z

This PR includes too large changes for updating snapshots:

105b817 : Modify runFixtureText to write serialized errors to snapshots.
59f07f7 , 9828d62 : Actually update snapshots following the above commit.
- the updating is executed via OVERWRITE=true TEST_ONLY=babel-parser make test-only

Re-reviewing

nicolo-ribaudo · 2021-03-27T00:02:07Z

Wow this PR is getting huge! 🚀😂

Could you also run BABEL_8_BREAKING=true OVERWRITE=true TEST_ONLY=babel-parser make test-only?

packages/babel-parser/test/expressions/is-expression-babel-parser/fail/8/output.json

nicolo-ribaudo · 2021-03-29T11:17:39Z

Maybe we could add a new test file (packages/babel-parser/test/error-codes.js) that asserts that:

import "foo" in a script throws BABEL_PARSER_SOURCETYPE_MODULE_REQUIRED
a b throws BABEL_PARSER_SYNTAX_ERROR
a b's error has a reasonCode property

thorn0 · 2021-03-31T21:04:11Z

packages/babel-parser/src/parser/error.js

@@ -73,7 +110,7 @@ export default class ParserError extends CommentsParser {
        }
      }
    }
-    return this._raise({ loc, pos }, message);
+    return this._raise({ code, loc, pos }, message);


It'd be good to add params as a property.
Use case: in Prettier, Unexpected reserved word 'yield' should be suppressed, Unexpected reserved word 'for' should be rethrown. prettier/prettier#10603

I'd prefer to split the error between UnexpectedKeyword and UnexpectedContextualKeyword if that works too, and avoid exposing too much internal details about how we build errors.

Yes, that's a better solution for that use case.

@thorn0 I was going to implement this, but I noticed that we already have two different errors:

UnexpectedKeyword for things like for, if, while, ...

UnexpectedReservedWord for things like yield, await, enum, ...

sosukesuzuki · 2021-04-03T02:29:12Z

Maybe we could add a new test file (packages/babel-parser/test/error-codes.js) that asserts that:

I added simple tests! f07223d

nicolo-ribaudo

Thanks!

I'll merge this to a feature branch (since we don't merge "New feature" PRs until we are ready for a minor version), so that you or someone else can work on #13033 (comment) on top of this one.

sosukesuzuki added pkg: parser area: errors labels Mar 21, 2021

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sosukesuzuki force-pushed the introduce-error-code branch from 0a70716 to 874ddd6 Compare March 24, 2021 15:15

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sosukesuzuki force-pushed the introduce-error-code branch from 9413b1f to 59f07f7 Compare March 26, 2021 16:46

nicolo-ribaudo added this to the v7.14.0 milestone Mar 26, 2021

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packages/babel-parser/test/expressions/is-expression-babel-parser/fail/8/output.json Outdated Show resolved Hide resolved

nicolo-ribaudo added the PR: New Feature 🚀 A type of pull request used for our changelog categories label Mar 27, 2021

sosukesuzuki force-pushed the introduce-error-code branch from 9828d62 to 2a737a1 Compare March 28, 2021 14:42

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sosukesuzuki added 5 commits April 3, 2021 11:03

Introduce error code

43187c0

Define new error template

3c798b1

Use ErrorTemplates type

9da92f3

Use makeErrorTemplate to reduce boilerplate

b1f3a79

Remove sourcetype related errors

0922ecf

sosukesuzuki added 7 commits April 3, 2021 11:03

Remove unnecessary type annotation

ebfce73

Fix unexpected signature

f914226

Introduce reasonCode

363ca85

Add missing error code

a7b4bc3

Add ErrorCodes objects

a0ef883

Fix conflicts

23e0bf1

Add tests for error codes

f07223d

sosukesuzuki force-pushed the introduce-error-code branch from 2a737a1 to f07223d Compare April 3, 2021 02:26

nicolo-ribaudo approved these changes Apr 3, 2021

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nicolo-ribaudo changed the base branch from main to feat-7.14.0/parser-updates April 3, 2021 17:30

nicolo-ribaudo changed the title ~~babel-parser: introduce error code~~ Introduce parser error codes Apr 3, 2021

nicolo-ribaudo merged commit 0240981 into babel:feat-7.14.0/parser-updates Apr 3, 2021

nicolo-ribaudo mentioned this pull request Apr 3, 2021

Parser features for 7.14.0 #13098

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Introduce parser error codes (#13033)

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Introduce parser error codes (#13033)

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thorn0 mentioned this pull request Apr 13, 2021

Re-enable error recovery for contextual keywords used as identifiers prettier/prettier#10603

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Introduce parser error codes #13033

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	export const ErrorMessages: ErrorTemplates = makeErrorTemplates({
	export const ErrorMessages = makeErrorTemplates({

Introduce parser error codes #13033

Introduce parser error codes #13033

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