Rename *.d.ts to *.d.mts

[tamuratak]

Rename *.d.ts to *.d.mts. Close #17241

TypeScript doesn't look up *.d.ts files from *.mjs. It only looks up *.d.mts files.

See

• https://www.typescriptlang.org/docs/handbook/modules/reference.html#file-extension-substitution

Notice that TypeScript can find types/src/pdf.d.ts even though it has the .d.ts extension because "types": "types/src/pdf.d.ts" is set in package.json.

[timvandermeij]

The change itself looks good, but why didn't the typing tests catch this before when we did the change to JavaScript modules? I would assume that gulp typestest would have fallen over if the types can't be loaded (see also https://github.com/mozilla/pdf.js/tree/master/test/types), so would it be possible to adapt the tests so that they fail without this patch and succeed with this patch applied?

[tamuratak]

I have added a test. Is it acceptable that the test depends on dist? It is much more reliable to test against the real target.

[tamuratak]

Now the test depends on generic as before.

[timvandermeij]

Yes, that should be correct because of the comment below it: type checking happens at compile time, not at run time, so the file itself is not actually run and therefore the exception is not actually thrown.

I have verified that the test do fail correctly if the type annotations are wrong, with the following diff:

diff --git a/test/types/legacy.ts b/test/types/legacy.ts
index 5a09b683d..7ed6b5805 100644
--- a/test/types/legacy.ts
+++ b/test/types/legacy.ts
@@ -2,7 +2,7 @@ import { getDocument } from "pdfjs-dist/legacy/build/pdf.mjs";
 import { EventBus } from "pdfjs-dist/legacy/web/pdf_viewer.mjs";
 
 class MainTest {
-  eventBus: EventBus;
+  eventBus: boolean;
   task: ReturnType<typeof getDocument> | undefined;
 
   constructor(public file: string) {
diff --git a/test/types/modern.ts b/test/types/modern.ts
index 06b892c91..c0720902f 100644
--- a/test/types/modern.ts
+++ b/test/types/modern.ts
@@ -2,7 +2,7 @@ import { getDocument } from "pdfjs-dist";
 import { EventBus } from "pdfjs-dist/web/pdf_viewer.mjs";
 
 class MainTest {
-  eventBus: EventBus;
+  eventBus: number;
   task: ReturnType<typeof getDocument> | undefined;
 
   constructor(public file: string) {

This results in the follow output with a non-zero exit code:

Couldn't compile TypeScript test:
test/types/legacy.ts(9,5): error TS2322: Type 'EventBus' is not assignable to type 'boolean'.
test/types/modern.ts(9,5): error TS2322: Type 'EventBus' is not assignable to type 'number'.

[timvandermeij]

Looks good to me, but please squash the commits before we can merge it. Thank you for fixing this and improving the tests!

[timvandermeij]

Thanks!