Don't ignore completions at source file locations

[Andarist]

When investigating Corsa's completions, I learned that it can't find completions for this case:
https://github.com/microsoft/typescript-go/blob/6e03d625d15ccaf727cb9a44b455eefb16f3d450/internal/fourslash/tests/gen/asOperatorCompletion_test.go#L13

In Corsa, there is no EndOfFileToken included in the SourceFile (yet? see microsoft/typescript-go#1257 ) and thus that token can't be found as the location (computed by getTouchingPropertyName(sourceFile, position)). So the location becomes simply the SourceFile itself.

But then, it turns out those completions stop working in Strada as soon as we include an extra newline at the end of the file, or if we add a comment after the as. In such situations, the found location becomes the SourceFile. I can't find a reason why the SourceFile locations would be deliberately ignored by this whole shouldIncludeSymbol function. Only 2 paths in it are actually considering location at all. I have a feeling, this condition might have been put in place to avoid checking location.parent as that's undefined for SourceFiles.

[typescript-bot]

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[typescript-bot]

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

[Copilot]

Pull Request Overview

This PR revises the logic for completions handling at source file locations and updates test baselines accordingly.

• Adjusts the condition in completions.ts to account for export assignments without prematurely excluding SourceFile locations.
• Updates several fourslash and baseline test files to reflect the new behavior.
• Adds a null-check in utilities.ts to improve robustness when accessing a node’s parent.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/cases/fourslash/asOperatorCompletion3.ts	Adds a test case checking completions when a comment follows the as operator.
tests/cases/fourslash/asOperatorCompletion2.ts	Updates the test case to verify completions without extra newline/comment.
tests/baselines/reference/tsserver/completions/in-project-reference-setup-with-existing-import.js	Modifies baseline output by replacing a class entry with an alias entry for MyClass.
tests/baselines/reference/tsserver/completions/in-project-reference-setup-with-existing-import-without-includeCompletionsForModuleExports.js	Aligns baseline output by substituting the removed class entry with an alias entry for MyClass.
src/services/utilities.ts	Introduces an explicit null-check for node.parent in internal import equals declaration.
src/services/completions.ts	Refactors the export assignment check to handle SourceFile locations by verifying location.parent exists.

Comments suppressed due to low confidence (2)

src/services/completions.ts:2742

• The updated condition now safely checks for location.parent before evaluating export assignment. Ensure that this change correctly handles cases where location is a SourceFile by design.

        if (location.parent && isExportAssignment(location.parent)) {

src/services/utilities.ts:523

• The added null check for node.parent improves robustness; consider verifying that similar patterns elsewhere in the codebase adhere to this safe-check approach.

    if (!node.parent) {

[Andarist]

All of this is simply outdented because I removed the wrapping if statement. Within the outdented codepaths I had to guard 2 places against missing location.parent and that's it.

cc @gabritto as you have a fresh context on all of this and related topics