New Tool: es-check

[Boshen]

See https://github.com/yowainwright/es-check

Usecases:

• to test whether oxc_transformer is correct
• to test whether your bundled app still has some higher ES features. For some apps or websites, they still require es5 for lower versions of ios safari or IE

Approach:

oxc_parser parses esnext, which means we are not going to add a ecmaVersion option to the parser. Instead we are just going to add a special linter. The the code setup can be copied from https://github.com/web-infra-dev/oxc/blob/main/crates/oxc_linter/examples/linter.rs

[magic-akari]

Something related: esbuild marks used features in the parser https://github.com/evanw/esbuild/blob/427ee6054401042f509c2b3a2d31bc6eebca655c/internal/js_parser/js_parser_lower.go#L42

[byteHulk]

hi @Boshen can I take on this issue?

[Boshen]

hi @Boshen can I take on this issue?

Have fun! Please be aware of our rules https://oxc-project.github.io/docs/contribute/rules.html and sure that you submit smaller PRs!

[byteHulk]

hi @Boshen Is it possible to do this just by checking(handwriting rules) the AST parsed by oxc_parser for new syntax for a particular version here?

And Do I still need to use the oxc_transformer package?

https://github.com/oxc-project/oxc/blob/774a257a66ca06b141a286c4e1336a81a6534be1/crates/oxc_linter/examples/linter.rs#L41

[Boshen]

hi @Boshen Is it possible to do this just by checking(handwriting rules) the AST parsed by oxc_parser for new syntax for a particular version here?

And Do I still need to use the oxc_transformer package?

https://github.com/oxc-project/oxc/blob/774a257a66ca06b141a286c4e1336a81a6534be1/crates/oxc_linter/examples/linter.rs#L41

It should be similar to how the linter is written, see

• https://github.com/oxc-project/oxc/blob/main/crates/oxc_linter/examples/linter.rs
• https://github.com/oxc-project/oxc/blob/main/crates/oxc_semantic/src/checker/javascript.rs

[byteHulk]

I see, but do I need to write the syntax matching rules by hand, or has someone else already done that part and I can just bring them in?

Like this?

AstKind::VariableDeclaration(stmt)
                if ecma_version < 6
                    && (stmt.kind == VariableDeclarationKind::Const
                        || stmt.kind == VariableDeclarationKind::Let) =>
            {
                The let declaration is not yet supported in the es5 environment.
                // errors...;
            }```

[Boshen]

I see, but do I need to write the syntax matching rules by hand, or has someone else already done that part and I can just bring them in?

Like this?

AstKind::VariableDeclaration(stmt)
                if ecma_version < 6
                    && (stmt.kind == VariableDeclarationKind::Const
                        || stmt.kind == VariableDeclarationKind::Let) =>
            {
                The let declaration is not yet supported in the es5 environment.
                // errors...;
            }```

do I need to write the syntax matching rules by hand

Yes, you need to write them by hand. All the tests from https://github.com/yowainwright/es-check/tree/main/tests has to be passed.

[Boshen]

I'm going to move this to another repository, in private for some experimentation.

[byteHulk]

我将把它转移到另一个存储库，私下进行一些实验。

ok

[Boshen]

We need this for the transformer after finishing Milestone 1 @Dunqing

[Boshen]

Ok this isn't the right direction, closing again.

[Boshen]

Reopen again because I need this to validate the transformer.