Improve logging and metrics around NoChange Errors

[robaiken]

What are you trying to accomplish?

Improve the logging and metrics signal around NoChangeErrors from npm/yarn/pnpm lockfile updates by ensuring the end-of-run "Dependencies failed to update" summary table renders a compact one-liner for no_change_error instead of pretty-printing the entire error_details payload (which includes the full command_traces array with stdout per command).

This builds on #15068, which converts what is today an opaque unknown_error (with a giant Sorbet stack trace and null details) into a structured no_change_error carrying useful diagnostic context. Without this change, that new structured payload drowns the summary in a multi-screen wall of text per failing dependency, hiding the very logging and metrics #15068 is adding.

Before this work (on main today) — meaningless unknown_error / null row preceded by ~40 lines of Sorbet stack trace:

2026/05/28 17:32:27 ERROR /home/dependabot/npm_and_yarn/lib/dependabot/npm_and_yarn/file_updater.rb:52:in 'Dependabot::NpmAndYarn::FileUpdater#updated_dependency_files'
2026/05/28 17:32:27 ERROR /home/dependabot/dependabot-updater/vendor/ruby/3.4.0/gems/sorbet-runtime-0.6.13208/lib/types/private/methods/call_validation.rb:294:in 'UnboundMethod#bind_call'
... (~40 more lines of Sorbet frames) ...
2026/05/28 17:32:27 ERROR bin/update_files.rb:48:in '<main>'

Dependabot encountered '1' error(s) during execution, please check the logs for more details.
+--------------------------------------------+
|       Dependencies failed to update        |
+------------+---------------+---------------+
| Dependency | Error Type    | Error Details |
+------------+---------------+---------------+
| qs         | unknown_error | null          |
+------------+---------------+---------------+

After #15068 alone — useful structured payload, but the summary table dumps it all:

updater | 2026/05/28 16:45:54 INFO Handled error whilst updating qs: no_change_error {dependencies: [{"name" => "qs", "version" => "6.15.2", ...}], updated_files: [], dependency_files: ["package.json", "pnpm-lock.yaml"], package_manager: "pnpm", reason: "no_files_updated", commands_succeeded: true, fallback_attempted: false, fallback_succeeded: nil, command_traces: [{package_manager: "pnpm", command: "update qs@6.15.2  --lockfile-only --no-save -r", ..., stdout: "(node:5109) [DEP0169] DeprecationWarning: `url.parse()` ... (multi-screen stdout) ... Done in 3.1s"}, {package_manager: "pnpm", command: "install --lockfile-only", ..., stdout: "... Done in 460ms", content_changed_after: false}]}

(plus the same payload pretty-printed inside the summary table)

After this PR — compact, scannable summary; full payload still flows to backend, logs, and metrics:

updater | +-----------------------------------------------------------------------------------------------------------------------------+
updater | |                                                Dependencies failed to update                                                |
updater | +------------+-----------------+----------------------------------------------------------------------------------------------+
updater | | Dependency | Error Type      | Error Details                                                                                |
updater | +------------+-----------------+----------------------------------------------------------------------------------------------+
updater | | qs         | no_change_error | package_manager=pnpm reason=no_files_updated command_traces=2 (full details sent to service) |
updater | +------------+-----------------+----------------------------------------------------------------------------------------------+

Anything you want to highlight for special attention from reviewers?

• The change is scoped strictly to local console rendering. Every downstream signal is preserved:
  • client.record_update_job_error(error_type:, error_details:) still sends the full structured payload to the backend.
  • log_no_change_diagnostics (per-trace info log lines from error_handler.rb) still runs unchanged.
  • service.increment_metric("updater.no_change", ...) still fires with all tags.
  • Sentry behavior is unchanged (and no_change_error was never sent to Sentry).
• The no_change_error branch in summarize_error_details is forward-compatible: it's dormant until Add no-change diagnostics for npm/yarn/pnpm lockfile updates #15068 lands, then activates automatically. This PR can be reviewed and merged independently.
• Alternative considered: dropping no_change_error rows from the table entirely (since the data is in logs/backend). Kept the row for at-a-glance visibility — open to dropping it if reviewers prefer.
• Drive-by fix: added require "github_api/dependency_submission" to updater/spec/dependabot/service_spec.rb to fix a pre-existing failure (uninitialized constant GithubApi) in the create_dependency_submission test.

How will you know you've accomplished your goal?

• All service_spec tests pass, including the two dependency_error_summary tests directly exercising the modified code path:

  $ bin/test --workdir updater bundler bundle exec rspec spec/dependabot/service_spec.rb
  Finished in 0.12 seconds (files took 1.71 seconds to load)
  43 examples, 0 failures
  

• Manual verification via script/dependabot update -f tmp/nc.yaml against a pnpm fixture that produces a no-change result — observed the compact summary row shown above instead of the verbose payload.

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.

[Copilot]

Pull request overview

Condenses the no_change_error rendering in the updater's end-of-run "Dependencies failed to update" summary table. Previously each row pretty-printed the full error_details payload (including all command_traces stdout), producing a wall of text. The PR delegates the Error Details cell to a new summarize_error_details helper that renders a compact one-liner for no_change_error, while preserving existing behavior (and full payload telemetry) for all other error types.

Changes:

• Add summarize_error_details helper in Dependabot::Service and use it in dependency_error_summary for enhanced error details.
• Add missing require "github_api/dependency_submission" in service spec to fix pre-existing load failure.

Show a summary per file

File	Description
updater/lib/dependabot/service.rb	New private summarize_error_details helper renders one-line summary for no_change_error; falls back to JSON.pretty_generate for other error types.
updater/spec/dependabot/service_spec.rb	Adds require "github_api/dependency_submission" to fix uninitialized constant GithubApi in existing test.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 0

[yeikel]

A small change that helps a lot. Thank you!