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Phase 10. TargetNpmLibrary emit

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MEPMEP-72 §Phases
StatusNOT STARTED
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Gate​

TestPhase10NpmLibrary in package3/typescript/library/phase10_test.go: subtests emit_package_json, emit_dist_mjs, emit_dts_declarations, exports_map_roundtrip, publish_dry_run, golden_corpus. The first synthesises a package.json from a representative Mochi package's mochi.toml's [ts.publish] section and asserts the JSON matches the golden. The second runs the MEP-52 phase 1+ emitter against examples/hello/hello.mochi and asserts the emitted .mjs runs under Node 22 and produces Hello, World!. The third invokes tsc --declaration --emitDeclarationOnly against the emitted .mjs and asserts the .d.ts round-trips through the ApiSurface ingest (phase 3) without skips. The fourth asserts the exports map resolves correctly for require, import, and types conditions. The fifth runs npm publish --dry-run against a representative package and asserts the printed package contents include the expected files. The sixth runs against three end-to-end Mochi packages.

Lowering decisions​

The build target is selected via:

[ts.publish]
target = "npm-library"
package-name = "@mochi/example"
version = "0.1.0"
registry = "https://registry.npmjs.org"
license = "Apache-2.0"
homepage = "https://example.com"
description = "Example Mochi package published to npm"

The emitter produces:

target/ts/npm-library/
  package.json
  README.md (copied from $MOCHI_PROJECT_ROOT/README.md)
  LICENSE (copied from $MOCHI_PROJECT_ROOT/LICENSE)
  dist/
    index.mjs       # MEP-52 phase 1+ emit, ESM
    index.cjs       # MEP-52 phase 1+ emit, CJS (when [ts.publish] dual = true)
    index.d.ts      # tsc --declaration --emitDeclarationOnly emit
    index.d.cts     # tsc --declaration --emitDeclarationOnly emit (CJS variant)
    index.mjs.map   # MEP-52 phase 16 source-map
    index.cjs.map

The synthesised package.json carries:

{
  "name": "@mochi/example",
  "version": "0.1.0",
  "description": "Example Mochi package published to npm",
  "license": "Apache-2.0",
  "homepage": "https://example.com",
  "type": "module",
  "main": "./dist/index.cjs",
  "module": "./dist/index.mjs",
  "types": "./dist/index.d.ts",
  "exports": {
    ".": {
      "types": "./dist/index.d.ts",
      "import": "./dist/index.mjs",
      "require": "./dist/index.cjs",
      "default": "./dist/index.mjs"
    }
  },
  "files": ["dist", "README.md", "LICENSE"],
  "sideEffects": false,
  "publishConfig": {
    "access": "public",
    "provenance": true
  }
}

The "publishConfig" "provenance": true flag is the npm Trusted Publishing trigger; when set, npm publish automatically generates a Sigstore attestation.

The .d.ts generation uses the bundled TypeScript compiler (TS 5.6, same version as the ingest helper). The compiler runs against target/ts/npm-library/dist/index.mjs with --declaration --emitDeclarationOnly --rootDir=dist --outDir=dist. The phase asserts the output .d.ts round-trips through ingest (phase 3) → ApiSurface → re-emit → cross-check against the Mochi source's declared signatures. A divergence indicates a bug in the MEP-52 emitter; the gate fails loudly.

The dual CJS + ESM emit is opt-in via dual = true. The default is ESM-only; npm's modern ecosystem is converging on ESM (Node 22 LTS supports ESM at parity with CJS).

Files changed​

FilePurpose
package3/typescript/library/npm.goEmitNpmLibrary, RenderPackageJSON, RunTsc
package3/typescript/library/exports.goexports-map synthesiser
package3/typescript/library/dts.gotsc invocation wrapper
package3/typescript/library/phase10_test.goTestPhase10NpmLibrary sentinel

Test set​

6 subtests as listed in the Gate section.

Cross-references​