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feat(typescript-estree): add `parseWithNodeMaps` API #2760

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merged 1 commit into from Nov 12, 2020
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@bradzacher bradzacher commented Nov 12, 2020

Ref: prettier/prettier#9636

This allows consumers to reach into the underlying TS AST in cases where our AST doesn't quite solve the use case.

Motivating example:

We don't (currently) error for code unless TS itself throws an error.
TS is very permissive, but that leads to some weird (and invalid) code we don't error for, and don't include in the AST.
For example - this is syntactically valid in the TS parser, but they emit a semantic error (we currently ignore semantic errors as they're expensive to calculate)

@decorator
enum Foo {
  A = 1
}

As it's not a valid place for a decorator - we do not emit its information in the ESTree AST, but as TS treats this as a semantic error - it is parse-time valid.
This creates weird states for consumers wherein they cannot see a decorator exists there, which can cause them to ignore it entirely.
For linting - this isn't a problem. But for something like prettier - this means that they'll delete the decorator at format time!
This is very bad.

Until we implement a solution for #1852 - this will allow consumers to bridge the gap themselves.

Ref: prettier/prettier#9636

This allows consumers to reach into the underlying TS AST in cases where our AST doesn't quite solve the use case.

Motivating example:

We don't (currently) error for code unless TS itself throws an error.
TS is _very_ permissive, but that leads to some weird (and invalid) code we don't error for, and don't include in the AST.
For example - this is _syntactically_ valid in the TS parser, but they emit a _semantic_ error:
```ts
@decorator
enum Foo {
  A = 1
}
```
As it's not a valid place for a decorator - we do not emit its information in the ESTree AST, but as TS treats this as a semantic error - it is parse-time valid.
This creates weird states for consumers wherein they cannot see a decorator exists there, which can cause them to ignore it entirely.
For linting - this isn't a problem. But for something like prettier - this means that they'll delete the decorator at format time!
This is very bad.

Until we implement a solution for #1852 - this will allow consumers to bridge the gap themselves.
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@typescript-eslint typescript-eslint bot commented Nov 12, 2020

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@bradzacher bradzacher merged commit 9441d50 into master Nov 12, 2020
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@bradzacher bradzacher deleted the parseWithNodeMaps branch Nov 12, 2020
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