fix: invalid lookup for null context in field resolvers

[Noroth]

closes #2573

Summary by CodeRabbit

• Tests
  • Expanded test coverage for null project query handling to ensure proper null propagation without invoking unnecessary field resolvers
  • Added validation across nested fields, recursive paths, and aliased field scenarios when querying non-existent projects

Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.
• Documentation has been updated on https://github.com/wundergraph/cosmo-docs.
• I have read the Contributors Guide.

[github-actions]

Router-nonroot image scan passed

✅ No security vulnerabilities found in image:

ghcr.io/wundergraph/cosmo/router:sha-7c1fb84932aebbf73ec8593c82cace6d2f2f99a7-nonroot

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.40%. Comparing base (391bffe) to head (f7513b1).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2585      +/-   ##
==========================================
- Coverage   62.69%   62.40%   -0.30%     
==========================================
  Files         244      244              
  Lines       25776    25775       -1     
==========================================
- Hits        16161    16085      -76     
- Misses       8251     8314      +63     
- Partials     1364     1376      +12     

see 16 files with indirect coverage changes

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: c62441c8-58e7-48f9-afa6-c71aa5ed0bab

📥 Commits

Reviewing files that changed from the base of the PR and between a60de99 and f7513b1.

📒 Files selected for processing (2)

• router-tests/grpc_subgraph_test.go
• router-tests/router_plugin_test.go

🚧 Files skipped from review as they are similar to previous changes (2)

• router-tests/grpc_subgraph_test.go
• router-tests/router_plugin_test.go

---

Walkthrough

Adds test cases validating that querying non-existent projects returns null and prevents field resolver invocation. Tests cover top-level fields, nested subProjects, recursive resolvers, and aliased nested resolvers across two test files with minor formatting adjustments.

Changes

Cohort / File(s)	Summary
Null Propagation Tests router-tests/grpc_subgraph_test.go, router-tests/router_plugin_test.go	Adds three new test cases per file to validate that non-existent projects (id: 999) return null without invoking field resolvers, covering top-level fields, nested subProjects, recursive resolvers, and aliased nested paths. Includes minor formatting adjustment for __typename indentation in existing test blocks.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• wundergraph/cosmo#2464: Addresses field-resolver behavior in the same router-tests files with tests for nested resolver invocation semantics.
• wundergraph/cosmo#2088: Modifies the same test functions (TestGRPCSubgraph and TestRouterPluginRequests) with expanded test coverage.
• wundergraph/cosmo#2368: Updates the same router-tests files with changes to field resolver behavior validation tests.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix: invalid lookup for null context in field resolvers' accurately describes the main change: preventing field resolver invocation when parent context is null, addressing the core issue.
Linked Issues check	✅ Passed	The PR adds test cases validating that querying non-existent projects returns null without invoking field resolvers, which directly addresses issue #2573's requirement to skip field resolver calls on null parent fields.
Out of Scope Changes check	✅ Passed	All changes are test additions that directly support the fix for null context handling in field resolvers, with no unrelated modifications present.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@router/go.mod`:
- Line 34: The call to astnormalization.NewVariablesNormalizer() in
operation_processor.go must be updated to pass the new boolean argument
enableFieldArgumentMapping; locate the call to
astnormalization.NewVariablesNormalizer (near the variables normalization logic
around the operation processing) and change it to
astnormalization.NewVariablesNormalizer(true) or
astnormalization.NewVariablesNormalizer(false) depending on whether you want
field argument mapping enabled for this operation context; ensure any
surrounding code that assumes the previous behavior still works with the chosen
flag.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 24facee6-f58e-4800-adb5-e46a86fab264

📥 Commits

Reviewing files that changed from the base of the PR and between 4c5384d and a4ed067.

⛔ Files ignored due to path filters (2)

• router-tests/go.sum is excluded by !**/*.sum
• router/go.sum is excluded by !**/*.sum

📒 Files selected for processing (2)

• router-tests/go.mod
• router/go.mod

[Noroth]

Waiting on #2589 to build a clean version.