TypeScript path aliases ignore fallback targets after the first

[oleksii-tumanov]

Context

Reproduced on v8 at 12193a8. TypeScript compilerOptions.paths values are ordered fallback lists, but Graphify keeps only targets[0]. If that substitution is missing while a later one exists, the import edges target the missing path and are dropped during build.

Related to #147. The open #927 handles wildcard pattern matching; this case is only about target fallback order.

Reproducer

{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "$lib/*": ["generated/*", "src/lib/*"]
    }
  }
}

Only src/lib/types/type-helpers.ts exists:

// src/routes/page.ts
import type { Helper } from '$lib/types/type-helpers'

Current behavior

Relevant extract() output, path-sanitized:

{
  "source": "src_routes_page",
  "target": "<project>_generated_types_type_helpers",
  "relation": "imports_from",
  "context": "import",
  "confidence": "EXTRACTED",
  "source_file": "src/routes/page.ts",
  "source_location": "L1"
}

JS/TS files bypass the AST cache, so this extraction does not produce a graphify-out/cache/ast/... entry.

Expected

Try each configured target in order until one resolves. The example should target src_lib_types_type_helpers; if both targets exist, the first should still win.

[safishamsi]

Fixed on v8 (2133539). You're right — compilerOptions.paths values are ordered fallback lists and graphify was keeping only the first target.

The alias map now stores all targets in declared order, and resolution tries each in turn, returning the first whose candidate file exists on disk (matching tsc), falling back to the first candidate when none exist so no false edge is fabricated. Wildcards, baseUrl, and array extends are preserved. As part of the fix I also collapsed six duplicated inline alias-resolution loops into one helper, so this can't drift again. Added regression tests for second-target-wins, first-target-wins-when-both-exist, and none-exist. Ships in the next release. Thanks for the precise report.