feat(typescript-estree): added allowInvalidAST option to not throw on invalid tokens

[JoshuaKGoldberg]

PR Checklist

• Addresses an existing open issue: fixes Parsing: strictly enforce the produced AST matches the spec and enforce most "error recovery" parsing errors #1852
• That issue was marked as accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

Adds an opt-in allowInvalidAST option to @typescript-eslint/typescript-estree and @typescript-eslint/parser. It enables checks for some known cases where TypeScript reports a syntactic issue as semantic:

• Exported class declaration without a name (Bug: no-restricted-exports: Cannot read property 'name' of null eslint/eslint#15384)
• Decorator on interfaces or types (Decorator is removed when followed by an interface. prettier/prettier#4552)
• Variable declaration without statements (ESLint: Cannot read property 'loc' of undefined. Please see the 'ESLint' output channel for details. #441, indent throws TypeError: Cannot read property 'loc' of undefined eslint/eslint#14538)

Note that some previously reported cases seem to now be reported as syntactic issues by TypeScript:

• export (Results of weekly scheduled smoke test jsx-eslint/eslint-plugin-react#3178)
• import (Parsing: strictly enforce the produced AST matches the spec and enforce most "error recovery" parsing errors #1852 (comment))
• throw (Handle throw with no arguments in no-throw-literal eslint/eslint#13143)

Does not tackle more difficult cases:

• async inside a non-async function ([Bug] await on non-async function does not throw an error #2997)
• abstract members marked async (TypeScript 4.1 Syntax Support #2583 (comment))
• in on a primitive (TypeScript 4.2 Syntax Support #2935 (comment))
• Invalid modifiers on a MethodDefinition (readonly and declare invalid property for MethodDefinition. #2908 (comment))

[typescript-eslint]

Thanks for the PR, @JoshuaKGoldberg!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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[codecov]

Codecov Report

Merging #6247 (7144e90) into v6 (f98afd2) will decrease coverage by 0.09%.
The diff coverage is 33.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##               v6    #6247      +/-   ##
==========================================
- Coverage   87.81%   87.72%   -0.09%     
==========================================
  Files         365      365              
  Lines       12455    12479      +24     
  Branches     3669     3679      +10     
==========================================
+ Hits        10937    10947      +10     
- Misses       1158     1170      +12     
- Partials      360      362       +2     

Flag	Coverage Δ
unittest	87.72% <33.33%> (-0.09%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...pt-estree/src/parseSettings/createParseSettings.ts	89.79% <ø> (ø)
packages/typescript-estree/src/convert.ts	32.30% <26.47%> (+0.43%)	⬆️
packages/typescript-estree/src/node-utils.ts	65.10% <75.00%> (-0.33%)	⬇️
packages/typescript-estree/src/ast-converter.ts	100.00% <100.00%> (ø)
packages/eslint-plugin/src/rules/indent.ts	88.09% <0.00%> (-4.77%)	⬇️

[JoshuaKGoldberg]

I'm not so sure this is the right approach to fixing the issue. It'd be hard to add branching logic for every possible syntactic issue not reported as such by TypeScript.

Instead, I'll look at using our isolated program to catch them.

Let this PR serve as a reference for what this logic could look like. 🙂

Edit: the isolated program is too slow. We're going with this! 🚀

I renamed a property