feat: Add NAR URL normalization function and support dashes/underscores in hashes

[kalbasit]

Add Normalize() method to nar.URL to handle NAR URLs with embedded narinfo hash
prefixes. Some upstream caches (like nix-serve) serve NAR URLs with the narinfo
hash as a prefix (e.g., "narinfo-hash-actual-hash"). This method strips the prefix
by identifying the first separator (dash or underscore) and removing everything
before it.

Changes:

• pkg/nar/url.go: Add Normalize() method and supporting logic
• pkg/nar/hash.go: Update narHashPattern to allow dashes and underscores ([a-z0-9_-]+)
• pkg/nar/url_test.go: Add TestNormalize with three test cases (no prefix, dash-separated, underscore-separated)
• testdata/nar7.go: Update to use prefixed hash format for testing

This enables parsing and normalizing NAR URLs from sources that include hash
prefixes, which will be applied consistently across cache, storage, and test
layers in subsequent commits.

Part of #806
Closes #820

Co-Authored-By: Claude Haiku 4.5 noreply@anthropic.com

[dosubot]

Related Documentation

Checked 7 published document(s) in 1 knowledge base(s). No updates required.

^{How did I do? Any feedback?}  

[gemini-code-assist]

Summary of Changes

Hello @kalbasit, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces functionality to robustly handle NAR URLs that may contain an informational hash prefix, as seen in some upstream caches like nix-serve. By adding a Normalize() method to the nar.URL type and updating the hash pattern to recognize separators, the system can now consistently parse and standardize NAR hashes, ensuring compatibility and correct storage across various components.

Highlights

• NAR URL Normalization Function: Implemented a Normalize() method for nar.URL to strip narinfo hash prefixes from NAR URLs, standardizing the hash for storage. This addresses URLs served by caches like nix-serve that include a prefix (e.g., "narinfo-hash-actual-hash").
• Hash Pattern Expansion: Modified the narHashPattern regular expression to allow dashes (-) and underscores (_) in NAR hashes, accommodating the format of prefixed hashes.
• Comprehensive Testing: Added new test cases in pkg/nar/url_test.go for the Normalize() method, covering scenarios with no prefix, dash-separated prefixes, and underscore-separated prefixes.

Changelog

• pkg/nar/hash.go
  • Updated the narHashPattern regular expression to include dashes and underscores.
• pkg/nar/url.go
  • Added a new Normalize() method to the URL struct for stripping narinfo hash prefixes.
  • Implemented logic within Normalize() to identify and remove prefixes separated by dashes or underscores.
• pkg/nar/url_test.go
  • Added TestNormalize with multiple test cases to validate the new Normalize() method's behavior.
  • Included tests for URLs with no prefix, dash-separated prefixes, and underscore-separated prefixes.

Activity

• No human activity (comments, reviews, etc.) has been recorded on this pull request yet.

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[kalbasit]

• fix: harden NAR hash validation and improve URL parsing #842
• fix: harden the narinfo route pattern #841
• fix: harden the narinfo hash validation #840
• fix: Fix test data generation and skip signature verification #839
• fix: Improve NAR file serving and remove old URL prefix workaround #838
• fix: Apply NAR URL normalization in storage layer #837
• feat: Add NAR URL normalization function and support dashes/underscores in hashes #836 👈 (View in Graphite)
• main

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[gemini-code-assist]

Code Review

This pull request introduces a Normalize() function to handle NAR URLs with prefixes and updates the NAR hash pattern to allow dashes and underscores. While the feature is useful, the implementation of the Normalize function has a critical flaw. Its logic is complex and uses a weak heuristic that can incorrectly modify valid NAR hashes that happen to contain a separator. This could lead to data corruption or invalid hash errors downstream. I've provided a much simpler and more robust implementation that uses a stronger heuristic based on the known length of narinfo hashes. Additionally, the accompanying tests are not comprehensive enough to catch these issues, so I've recommended adding more test cases for edge scenarios.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.41%. Comparing base (184373f) to head (c2924c9).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #836   +/-   ##
=======================================
  Coverage   85.41%   85.41%           
=======================================
  Files           2        2           
  Lines         480      480           
=======================================
  Hits          410      410           
  Misses         65       65           
  Partials        5        5           

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[kalbasit]

Backport failed for release-0.8, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin release-0.8
git worktree add -d .worktree/backport-836-to-release-0.8 origin/release-0.8
cd .worktree/backport-836-to-release-0.8
git switch --create backport-836-to-release-0.8
git cherry-pick -x 20012d5c911eda931990e2076e37c4c6bc2d5be2 c2924c9a11dc9c9b792460f6f1da3eb16524d5b9