fix(http): add synchronous port binding to avoid false positive server start

[StarpTech]

Summary by CodeRabbit

• Bug Fixes

  • Improved error handling for server initialization with immediate detection of port binding failures and clearer error messages on startup.

• Tests

  • Added test coverage for server initialization and port binding scenarios.

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/docs-website.
• I have read the Contributors Guide.

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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: 9b4ecb0a-3074-44d2-adce-784364851f1c

📥 Commits

Reviewing files that changed from the base of the PR and between fe662bf and c125958.

📒 Files selected for processing (3)

• router/core/http_server.go
• router/core/http_server_test.go
• router/core/router.go

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Walkthrough

This PR modifies the HTTP server initialization flow to synchronously bind TCP ports during newServer instead of deferring binding to listenAndServe. The newServer function now returns an error on binding failure, which is propagated through the router's NewServer and Start methods. New test cases validate error handling for port binding failures and successes.

Changes

Cohort / File(s)	Summary
Server Binding Logic router/core/http_server.go	Refactored newServer to synchronously bind address using net.Listen("tcp", ...), return (*server, error), store listener as struct field, and updated listenAndServe to serve via pre-bound listener instead of ListenAndServe/ListenAndServeTLS.
Error Handling router/core/router.go	Updated NewServer and Start methods to capture and propagate errors from newServer with wrapped error messages (failed to create server).
Port Binding Tests router/core/http_server_test.go	Added three test cases: TestNewServer_PortBindingError (validates immediate error on already-bound address), TestNewServer_PortBindingSuccess (validates successful binding and cleanup), and TestRouter_Start_PortBindingError (validates router startup failure propagation).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix: add back NewServer #2546: Modifies router startup and server creation handling in router/core/router.go with overlapping initialization paths and error propagation logic.

🚥 Pre-merge checks | ✅ 2 | ❌ 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 (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically summarizes the main change: adding synchronous port binding to prevent false positive server starts, which aligns with the core implementation changes across all modified files.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

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[github-actions]

Router image scan passed

✅ No security vulnerabilities found in image:

ghcr.io/wundergraph/cosmo/router:sha-94e0b7b43eb2b5baf1d1a109011ffde320540a5f

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.35%. Comparing base (bcb4ed3) to head (c125958).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
router/core/http_server.go	75.00%	0 Missing and 2 partials ⚠️
router/core/router.go	75.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2730       +/-   ##
===========================================
+ Coverage   45.69%   63.35%   +17.65%     
===========================================
  Files        1032      249      -783     
  Lines      138960    26671   -112289     
  Branches     8629        0     -8629     
===========================================
- Hits        63504    16898    -46606     
+ Misses      73731     8408    -65323     
+ Partials     1725     1365      -360     

Files with missing lines	Coverage Δ
router/core/http_server.go	86.76% <75.00%> (+0.82%)	⬆️
router/core/router.go	69.99% <75.00%> (+0.20%)	⬆️

... and 787 files with indirect coverage changes

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