Use first @jsx/@jsxfrag pragma to match tsc behavior

[Copilot]

When a file contains multiple /** @jsx */ factory pragmas, tsc resolves to the first one but tsgo resolved to the last, producing divergent emit:

/** @jsx h */
/** @jsx g */
declare const h: any, g: any;
export const x = <div/>;

// tsc:  export const x = h("div", null);
// tsgo: export const x = g("div", null);  // before this change

The previous ast.GetPragmaFromSourceFile was "last one wins", which is correct for jsximportsource/jsxruntime (TypeScript reads length - 1) but wrong for the jsx/jsxfrag factory pragmas, where TypeScript reads index 0.

Changes

• internal/ast/utilities.go: add GetFirstPragmaFromSourceFile (first matching pragma, matching tsc pragmas[0]) and rename GetPragmaFromSourceFile to GetLastPragmaFromSourceFile (last matching pragma, matching tsc pragmas[length - 1]) for consistent naming, each documenting the tsc indexing it mirrors.
• internal/checker/jsx.go: use GetFirstPragmaFromSourceFile for all jsx/jsxfrag reads — factory resolution in getLocalJsxNamespace, the fragment branch of getJsxNamespace, and getJsxFragmentFactoryEntity, plus the checkJsxFragment existence checks. jsximportsource/jsxruntime in getJSXImplicitImportBase use GetLastPragmaFromSourceFile. Every call site was cross-checked against tsc behavior.
• testdata/tests/cases/compiler/jsxMultiplePragmas.tsx: regression test (the repro above) with baselines.

[jakebailey]

@copilot Now we have two funcs that do the same thing but differently. Their naming needs to be made consistent, and also both funcs and all users need to be cross-checked to make sure they match tsc behavior.

[Copilot]

Renamed for consistency: GetFirstPragmaFromSourceFile (first wins) and GetLastPragmaFromSourceFile (formerly GetPragmaFromSourceFile, last wins), each documenting the matching tsc indexing (pragmas[0] vs pragmas[length-1]). Cross-checked every call site against tsc: jsx/jsxfrag reads (factory resolution in getLocalJsxNamespace/getJsxNamespace/getJsxFragmentFactoryEntity, plus the checkJsxFragment existence checks) now use first; jsximportsource/jsxruntime in getJSXImplicitImportBase use last. (00f0c8c was the rename commit)

[jakebailey]

weird but ok

[Copilot]

Pull request overview

Aligns tsgo’s JSX pragma resolution with TypeScript/tsc by making @jsx/@jsxfrag use the first matching pragma in a file (instead of “last one wins”), while keeping @jsximportsource/@jsxruntime as last matching pragma. This reduces emit divergence for files containing multiple JSX factory pragmas.

Changes:

• Added GetFirstPragmaFromSourceFile and renamed the prior “last one wins” helper to GetLastPragmaFromSourceFile for explicit, behavior-revealing naming.
• Updated JSX checking/namespace/factory resolution to read @jsx/@jsxfrag via the “first pragma wins” helper.
• Added a compiler regression test plus reference baselines proving the emitted factory matches tsc (h(...) from the first pragma).

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/ast/utilities.go	Introduces explicit first/last pragma helpers and uses “last” for jsximportsource/jsxruntime lookups.
internal/checker/jsx.go	Switches jsx/jsxfrag resolution and related checks to use the first pragma for tsc parity.
testdata/tests/cases/compiler/jsxMultiplePragmas.tsx	New regression test covering multiple @jsx pragmas in one file.
testdata/baselines/reference/compiler/jsxMultiplePragmas.js	Reference emit baseline demonstrating factory uses the first pragma (h).
testdata/baselines/reference/compiler/jsxMultiplePragmas.types	Reference type baseline for the new test case.
testdata/baselines/reference/compiler/jsxMultiplePragmas.symbols	Reference symbol baseline for the new test case.
testdata/baselines/reference/compiler/jsxMultiplePragmas.errors.txt	Reference error baseline for the new test case.