Replace anyhow with custom error types using thiserror

[kixelated]

This PR replaces the anyhow crate with a custom error type hierarchy using thiserror, providing more structured and type-safe error handling throughout the moq-token crate.

Summary

Migrated from generic anyhow::Error to a custom Error enum with a specialized KeyError variant for cryptographic operations. This improves error semantics, enables better error handling patterns, and reduces external dependencies.

Key Changes

• New error module (error.rs): Introduced KeyError enum for key-specific errors and top-level Error enum that encompasses all error types in the crate

  • KeyError variants cover algorithm mismatches, missing keys, unsupported operations, and coordinate validation
  • Error enum aggregates KeyError and integrates with external error types (JSON, IO, Base64, JWT, RSA, etc.)
  • Defined Result<T> type alias as std::result::Result<T, Error>

• Updated key.rs: Replaced all anyhow::Result with crate::Result and converted error handling:

  • Replaced bail!() and anyhow::anyhow!() with explicit KeyError variants
  • Simplified error propagation using ? operator instead of match expressions
  • Removed unnecessary Context trait usage, using ok_or() for Option conversions

• Updated generate.rs: Migrated to custom error types and simplified RSA key generation error handling

• Updated set.rs: Replaced anyhow::Result with crate::Result and removed verbose error wrapping in to_public_set()

• Updated algorithm.rs: Changed FromStr::Err type from anyhow::Error to Error with proper variant usage

• Updated claims.rs: Replaced anyhow::bail!() with crate::Error::UselessToken

• Updated Cargo.toml: Replaced anyhow = "1" dependency with thiserror = "2"

Notable Implementation Details

• Error types use #[from] attributes for automatic conversion from underlying error types
• Preserved all error context and messages through descriptive error variants
• Maintained backward compatibility with public API return types (still return Result<T>)
• Conditional compilation for jwks-loader feature errors

https://claude.ai/code/session_01AaDSYmsVmbhVA6iSFJ6yNa

[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: dfdb1d75-5d62-4b52-b9d2-763e1bd7c8ec

📥 Commits

Reviewing files that changed from the base of the PR and between 467b326 and b1519c8.

📒 Files selected for processing (5)

• rs/moq-token/Cargo.toml
• rs/moq-token/src/claims.rs
• rs/moq-token/src/generate.rs
• rs/moq-token/src/key.rs
• rs/moq-token/src/set.rs

🚧 Files skipped from review as they are similar to previous changes (5)

• rs/moq-token/Cargo.toml
• rs/moq-token/src/claims.rs
• rs/moq-token/src/generate.rs
• rs/moq-token/src/key.rs
• rs/moq-token/src/set.rs

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Walkthrough

The pull request replaces anyhow with thiserror in the crate manifest and introduces a new error module that defines KeyError, Error, and a Result<T> alias. Numerous public APIs and internal helpers across modules (algorithm, claims, generate, key, set) were changed from returning anyhow::Result to crate::Result, and error construction/propagation was refactored to return explicit Error/KeyError variants instead of using anyhow-based bail/context. lib.rs now re-exports the new error types.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 21.43% 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
Title check	✅ Passed	The title accurately and concisely describes the main change: replacing anyhow with custom error types using thiserror. It clearly identifies the primary refactoring objective of the PR.
Description check	✅ Passed	The description comprehensively explains the migration from anyhow to custom error types, detailing the new error module structure, changes across each affected file, and implementation details. It is directly related to the changeset.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/moq-token-thiserror-SN5wz

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch claude/moq-token-thiserror-SN5wz

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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 `@rs/moq-token/src/generate.rs`:
- Around line 79-81: The code accesses RSA CRT fields via key.dp(), key.dq(),
and key.qinv() and uses expect(), which will panic because those Options are
only populated after precompute(); call key.precompute().map_err(|e| …)? (or
otherwise invoke the rsa crate's precompute method) before reading dp/dq/qinv in
generate.rs, then replace the expect() calls with proper error propagation
(e.g., .ok_or_else(|| YourError::MissingCrtField("dp"))? ) so the function
returns a Result on failure instead of panicking.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 24048dc1-112f-4110-89e8-06482215109c

📥 Commits

Reviewing files that changed from the base of the PR and between bb81dce and 467b326.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (8)

• rs/moq-token/Cargo.toml
• rs/moq-token/src/algorithm.rs
• rs/moq-token/src/claims.rs
• rs/moq-token/src/error.rs
• rs/moq-token/src/generate.rs
• rs/moq-token/src/key.rs
• rs/moq-token/src/lib.rs
• rs/moq-token/src/set.rs