Write generated/generator.json only after message generation completes

[KR-Ravindra]

Problem

If message generation does not run to completion, rclnodejs.init() keeps treating the partial generated/ tree as complete. Every interface that was never written then fails with MESSAGE_NOT_FOUND on every start, and the only way out is to delete generated/ by hand. The two realistic ways to get there are the generating process being killed part-way (SIGKILL/OOM during npm install, Ctrl-C on generate-ros-messages, CI/container teardown) and any single package failing to generate (EACCES, ENOSPC, a malformed interface). In the second case npm install also exits 0, because the postinstall script only logs the error, so the partial tree is left behind silently.

Root cause

• rosidl_gen/index.cjs:87-90 copies generator.json (the version marker init() uses to decide whether regeneration is needed) into generated/ before the per-prefix generateInPath() loop at rosidl_gen/index.cjs:103-105 has generated a single interface file.
• index.js:422-424 (getCurrentGeneratorVersion() / forced) only regenerates when that file is absent or carries an older version, so a partial tree with a current-version marker is never regenerated.
• scripts/generate_messages.cjs:36-38 catches the error, prints Caught error: ... and returns normally, so the process exits 0.

Fix

• rosidl_gen/index.cjs: write generated/generator.json last, after the generateInPath() loop. generated/ is now created with fse.mkdirs() up front (the generator.json copy used to create it implicitly). A tree left behind by an interrupted or failed run has no marker, getCurrentGeneratorVersion() returns null, and init() regenerates it on the next start with no other change.
• scripts/generate_messages.cjs: process.exit(1) in the catch handler so npm install and npx generate-ros-messages report the failure instead of succeeding with a partial tree.
• test/test-messsage-generation-overlay.js: regression test that points AMENT_PREFIX_PATH at a prefix whose ament index lists a .msg file that does not exist, runs generateAll(true), and asserts that it fails and that no generated/generator.json was written.

How tested

New test against the unmodified generator:

  override interface in overlay tests
    1) failed generation leaves no generator.json marker
  0 passing (100ms)
  1 failing
  1) override interface in overlay tests
       failed generation leaves no generator.json marker:
      AssertionError [ERR_ASSERTION]: Expected no generator.json after a failed generation
      + expected - actual
      -false
      +true

With the fix:

  override interface in overlay tests
    ✔ failed generation leaves no generator.json marker (148ms)
  1 passing (156ms)

Also checked that a successful generateAll(false) followed by generateAll(true) still produces generated/generator.json, generated/package.json and generated/srv_msg/, and that node scripts/generate_messages.cjs now exits 1 when a package fails to generate (generated/ is left without generator.json). npx prettier --check and npx eslint pass on the changed files.

Links

• Interrupted or failed message generation leaves a partial generated/ tree that init() treats as complete (MESSAGE_NOT_FOUND until generated/ is deleted by hand) #1594
• Earlier reports of users stuck in this state: Incomplete installation process on v0.11.0 - Message generation failing #546, Types for creating an Action Client not Updating with Sources Action Message Types #688, Interface broken with custom msg: "Error The message required does not exist: {ros2_package}, msg, {ros2_msg} at /{server_dir}/node_modules/rclnodejs/generated/" #1254

This change was prepared with an AI agent operated by KR-Ravindra, who reviewed and tested it.

[coveralls]

coverage: 90.812% (+0.007%) from 90.805% — KR-Ravindra:fix/write-generator-marker-last into RobotWebTools:develop

[KR-Ravindra]

Round 1 self-review.

Checked against develop: rosidl_gen/index.cjs copies generator.json into generated/ before the generateInPath() loop, init() only regenerates when that marker is missing or older than the generator, and scripts/generate_messages.cjs logs the error and returns normally, so the description matches the code.

1. Marker is now written after the loop and generated/ is created with fse.mkdirs() up front (the copy used to create it implicitly), so an interrupted or failed run leaves no marker and the next init() regenerates. Looks correct.
2. process.exit(1) in the postinstall catch makes npm install report the failure instead of exiting 0 with a partial tree.
3. The new mocha case uses the file's existing generateMessages() / GENERATED_PATH helpers, restores AMENT_PREFIX_PATH and removes the temp prefix in finally.

CI: full ROS 2 matrix (humble, jazzy, kilted, lyrical, rolling; arm64 + x64; pixi builds) green, coverage unchanged. Marking ready.

[Copilot]

🟢 Approval recommended

The change directly addresses the reported partial-generation failure mode and adds a targeted regression test, with only a minor logging improvement suggested.

Pull request overview

This PR hardens ROS message generation so a partially generated generated/ tree is no longer treated as complete by rclnodejs.init(), and generation failures correctly surface as non-zero exits (preventing silent broken installs).

Changes:

• Delay writing generated/generator.json until after all interfaces finish generating, so interrupted/failed runs leave no “complete” marker.
• Make scripts/generate_messages.cjs exit with status 1 on generation errors (so npm install/npx generate-ros-messages fail loudly).
• Add a regression test ensuring failed generation does not leave generated/generator.json behind.

File summaries

File	Description
rosidl_gen/index.cjs	Moves the version marker write to the end of successful generation and ensures generated/ exists before writing other outputs.
scripts/generate_messages.cjs	Ensures message generation failures propagate as a non-zero process exit.
test/test-messsage-generation-overlay.js	Adds a regression test for the “no marker after failed generation” behavior.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 1
• Review effort level: Lite

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[minggangw]

lgtm, merging