ts.preProcessFile finds import in template string after conditional expression with template strings

[jakebailey]

Bug Report

🔎 Search Terms

preProcessFile template string conditional expression

🕗 Version & Regression Information

• This is the behavior in every version I tried.

💻 Code

a ? `&${a}` : `#${b}`;

`import("${moduleSpecifier}").${id}`;

🙁 Actual behavior

{
  referencedFiles: [],
  typeReferenceDirectives: [],
  libReferenceDirectives: [],
  importedFiles: [ { fileName: '${moduleSpecifier}', pos: 32, end: 50 } ],
  isLibFile: false,
  ambientExternalModules: undefined
}

🙂 Expected behavior

{
  referencedFiles: [],
  typeReferenceDirectives: [],
  libReferenceDirectives: [],
  importedFiles: [],
  isLibFile: false,
  ambientExternalModules: undefined
}

This is somewhat similar to #47597 or #30878. I found this while fixing monaco for the module transform, which has a higher emit target that enables template strings. See: https://github.com/microsoft/TypeScript-Make-Monaco-Builds/actions/runs/3187364358/jobs/5198859864#step:7:343

[a-tarasyuk]

@jakebailey Do we need to skip this import or add it to importedFiles ? This issue #30878 is that preProcessFile didn't process imports after the template strings.

[jakebailey]

Definitely skip; this is just text in a string, and the "filename" being found is not syntactically valid at all.

preProcessFile should behave exactly as though it has been implemented by running the full parser and then extracting the import expression nodes, but faster, I guess.