fix(cli): honor --src-lang for directory JSON/URL inputs

[schani]

Bug

#1179 — Quicktype generates models for json-schema simpletypes when generating from a directory to a single file

Running quicktype ./schemas -o api.swift -l swift (or quicktype --src-lang schema ./schemas -l swift) against a directory of *.json-named JSON Schema files produced bogus structs/enums built from the schema's own keys ($schema, type, pattern) — e.g. an enum whose cases are the schema's pattern regex strings — instead of generating types for the values the schema describes.

Root cause

Directory-mode input classification in src/index.ts (samplesFromDirectory / readFilesOrURLsInDirectory) decided whether each file was JSON data or JSON Schema purely from its file extension: .json/.url were always treated as kind: "json" and only .schema as kind: "schema". Crucially, getSources called samplesFromDirectory(dataDir, options.httpHeader) without ever passing options.srcLang, so an explicit --src-lang schema had no effect at all for directory sources — .json-named schema files were always parsed as JSON data samples.

This contrasts with the single-file path, where typeSourcesForURIs already switches on options.srcLang and forces every URI to kind: "schema" when --src-lang schema is given, regardless of extension — which is why a single file (quicktype --src-lang schema schema.json) worked correctly while the same file inside a directory did not.

Fix

.json/.url files discovered in a directory are now routed through the existing typeSourcesForURIs helper (the same one used for single-file/URL sources), so --src-lang is honored consistently whether the input is a single file or a directory. .schema/.gqlschema/.graphql extension handling, and the default (--src-lang json) behavior for .json files, are unchanged.

Test coverage

This bug is about directory-mode source classification, which the fixture harness (which invokes quicktype on one file at a time) cannot express. Added test/unit/directory-input.test.ts, which builds a temp directory of two schema documents named *.json and asserts that quicktype({ srcLang: "schema", src: [dir], ... }) produces the expected typealiases and does not emit a struct built from the schema's own keys. Confirmed this test fails on unfixed code and passes after the fix.

Verification performed locally

• npm run build — passes.
• npx vitest run test/unit — 171/171 tests pass (no regressions).
• Re-ran the exact repro (--src-lang schema against a directory of .json-named schema files) — now correctly produces typealias Name = String / typealias AnotherName = String instead of bogus structs.
• Verified .schema-extension directories (already-correct case) still work, and that default (--src-lang json, no explicit override) directories of .json files still correctly generate JSON-derived structs (no regression to existing default behavior).
• QUICKTEST=true FIXTURE=schema-typescript script/test — 70/70 tests pass, exit code 0.
• FIXTURE=schema-swift (matching the language used in the original issue) could not be run in this environment because the Swift toolchain (swiftc) is not installed here; CI will cover this fixture.

Fixes #1179

🤖 Generated with Claude Code

[github-actions]

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✅ Generated outputs are unchanged between the PR base and head revisions.

[github-actions]

No generated-output differences

✅ Generated outputs are unchanged between the PR base and head revisions.