nodejs: resolve migrate+generate diffs for google-cloud-compute

[julieqiu]

Once we finish #4843, we should repeat these steps and resolve diffs for google-cloud-compute.

  cd /path/to/googleapis/librarian
  go install ./cmd/librarian && go install ./tool/cmd/migrate
  cd /path/to/googleapis/google-cloud-node
  git fetch upstream && git reset --hard upstream/main
  migrate .
  librarian generate google-cloud-compute
  git diff --stat

[julieqiu]

@pearigee @quirogas assigning to y'all for next steps

[quirogas]

As of this comment, the current diff from running migrate and generate for google-cloud-compute is massive.

Diff Summary (after running migrate+generate)

1135 files changed, 150859 insertions(+), 323603 deletions(-)

Categorization of Changes

1. Expected Deletions (Cleanup)

• packages/google-cloud-compute/.OwlBot.yaml
• packages/google-cloud-compute/.readme-partials.yaml

2. Deprecated / Removed Protos & Code

• packages/google-cloud-compute/protos/google/cloud/compute/v1small/compute_small.proto
• packages/google-cloud-compute/src/v1small/
• packages/google-cloud-compute/test/gapic_addresses_v1small.ts

Actionable Item: v1small should be removed from librarian.yaml because it is marked for "testing and prototyping" and its name violates Node.js versioning conventions, which causes generate to fail. @pearigee WDYT?

3. Structural Regressions (Missing Helpers)

Helper methods like projectPath are missing from all client classes (e.g., AddressesClient).
Actionable Item: Investigate why the helpers are missing. Look at #4744 commnet for guidance.

4. Massive Code Drift

The majority of the 400k+ line diff resides in:

• packages/google-cloud-compute/protos/protos.{js,d.ts,json}
• packages/google-cloud-compute/src/v1/*.ts
• packages/google-cloud-compute/test/*.ts

Unlike standard GAPICs (like Secret Manager), Compute is a "Diregapic" (http://go/cloudsdk-compute). The generated code shows significant differences in transport handling (REST vs gRPC) and auth initialization.
Actionable Item: Verify if these changes are expected improvements in the modern generator or regressions in feature parity.

5. Stale Data (Metadata & Copyright)

Generated samples and metadata files have version resets (0.1.0) and copyright year updates.

Actionable Items::

• Short term we can update version manually to reflect the correct version, but long term we have to create a bug that tracks why the version reset is happening and determine if it is still persistent.
• Update copyright year for all packages to 2026.

[quirogas]

Update on investigation findings.

What We Found

1. Transport Logic Regression: The massive code churn in src/ and test/ was caused by the generator falling back to the default gRPC transport generation. google-cloud-compute is a Discovery-based API that requires REST-only transport and specific initialization logic.
2. The diregapic Flag: Checking the upstream google/cloud/compute/v1/BUILD.bazel revealed that nodejs_gapic_library explicitly sets diregapic = True.
3. Librarian Gap: Librarian's Node.js configuration does not pass the --diregapic flag to the TypeScript generator.
4. Generator CLI Bug: When we manually passed --diregapic via extra_protoc_parameters, the gapic-generator-typescript CLI wrapper crashed with ERROR: Protos do not define any service. We discovered that the wrapper uses yargs to parse arguments but failed to define diregapic as a .boolean(). Consequently, yargs treated --diregapic as a string flag and consumed the next argument—which happened to be compute.proto—leaving only common_resources.proto to be compiled.
5. Path Helpers: We verified the baseline and confirmed that google-cloud-compute never had standard GAPIC path helpers (like projectPath). Their absence is expected for this specific API.

How We Resolved It (Exploration Phase)

As a proof-of-concept, we applied several local modifications to verify this root cause:

1. Modified Librarian (internal/config/language.go and internal/librarian/nodejs/generate.go) to support diregapic: true at the API level and pass the --diregapic flag to the generator.
2. Patched the local gapic-generator-typescript.js CLI wrapper to explicitly declare .boolean('diregapic') to prevent argument swallowing.
3. Re-ran generation on a clean workspace.

Result: The diff dropped from 400k+ lines to 513 files changed, 6974 insertions(+), 54588 deletions(-).

Actionable Follow-up Items

1. Label and Investigate Remaining Diffs: There are still ~60,000 line diff we have to review to comfirm that every change is either expected drift (e.g., metadata name changes) or an improvement.
2. Update Librarian (Node.js Generator): Open a PR to officially add DIREGAPIC support to NodejsAPI in librarian.yaml and append the --diregapic flag in buildGeneratorArgs.
3. Update the migrate Tool: Open a PR to enhance the migrate command to detect diregapic = True within the nodejs_gapic_library Bazel rules and automatically set diregapic: true in the generated librarian.yaml.
4. Investigate the TypeScript Generator Bug: Determine why the generator required a manual CLI shim fix. We must decide if the CLI wrapper requires a permanent upstream fix in the gapic-generator-typescript repository or if there is a conflict in how Librarian sequences arguments.