Microsoft/TypeScript

Suggestion: Change `Diagnostic.file` to be `SourceFileLike` instead of `SourceFile`.

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#18,013 opened on Aug 24, 2017

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Domain: APIHelp WantedSuggestion

Description

Diagnostic.file is of type SourceFile which forces plugins to cast a non-SourceFile to a SourceFile to report diagnostic messages and guess which parts of SourceFile are not used by tsserver.

Consider changing file to be something like SourceFileLIke or SourceMapSource that specifies the exact requirements that must be supplied by plugins for this field.

Contributor guide

Tech stack
typescript
Domain
developer experienceapi
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
TypeScript compiler internalsplugin system
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
The issue proposes changing the `Diagnostic.file` type from `SourceFile` to a more generic interface like `SourceFileLike` that only includes the properties actually used by `tsserver`. Investigate the current usage of `Diagnostic.file` in the TypeScript codebase, especially in `src/compiler/diagnostic.ts` and related plugin APIs. Review the TypeScript plugin protocol to understand constraints. The existing comment and reactions suggest minimal discussion; consider reaching out to maintainers for alignment on the desired contract.