fix(typescript-estree): change source of ExportNamedDeclaration to Literal from Expression

[sosukesuzuki]

source of ExportNamedDeclaration is Literal in estree.

If this is your intention, close this.

[typescript-eslint]

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[bradzacher]

This is actually currently done on purpose.
The TS parser is incredibly forgiving - and so it gives us a bad AST.
We don't currently enforce the AST matches the ESTree structure - so in this case import foo from bar is valid code in our parser (as is export { foo } from 1 + 1.

We have two options:

1. wait until we've done Parsing: strictly enforce the produced AST matches the spec and enforce most "error recovery" parsing errors #1852 and thus have parser errors for bad code
2. add validation in this diff to enforce that it is a string literal.

I'm happy with either - depends on if you've got time to do the extra work for (2).

[sosukesuzuki]

@bradzacher Thanks you for telling me.

I'm happy with either - depends on if you've got time to do the extra work for (2).

I can work for implement option (2).

However, one question. Why source of ImportDeclaration is Literal? We can specify any expression to source of ImportDeclaration same as ExportNamedDeclaration.

[sosukesuzuki]

I've pushed commits to add assertion for module specifiers, but I'm not sure it is correct way.

[codecov]

Codecov Report

Merging #3763 (5b66c4c) into v5 (a752638) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##               v5    #3763      +/-   ##
==========================================
- Coverage   92.68%   92.68%   -0.01%     
==========================================
  Files         327      325       -2     
  Lines       11351    11349       -2     
  Branches     3201     3203       +2     
==========================================
- Hits        10521    10519       -2     
  Misses        369      369              
  Partials      461      461              

Flag	Coverage Δ
unittest	92.68% <100.00%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
packages/typescript-estree/src/convert.ts	98.28% <100.00%> (+0.01%)	⬆️
packages/visitor-keys/src/visitor-keys.ts
packages/visitor-keys/src/get-keys.ts

[bradzacher]

LGTM - thanks for this!