feat: corn source

[robjtede]

Noticed this was a file type supported by config and seems pretty cool actually.

Summary by CodeRabbit

• New Features

  • Added optional CORN configuration support (gated by an off-by-default feature) to load settings from .corn files and CORN string literals.

• Documentation

  • Updated configuration sources docs to include CORN format and feature gating notes.

• Tests

  • Added tests covering CORN parsing and secret-field handling.

• Chores

  • Adjusted private toolchain downgrade recipe for compatibility.

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds CORN format support behind a new corn-0_10 crate feature: introduces a CornSource type, wires a corn extension into FileSource parsing, adds feature-gated tests and docs, and registers an optional libcorn dependency in Cargo.toml.

Changes

Cohort / File(s)	Summary
Cargo Manifest confik/Cargo.toml	Added feature corn-0_10 = ["dep:libcorn-0_10"] and optional dependency libcorn-0_10 = { package = "libcorn", version = "0.10", optional = true }.
Docs confik/src/lib.md, confik/CHANGELOG.md	Documented .corn support and new CornSource; added changelog entry under Unreleased.
Public API / Module Exports confik/src/lib.rs, confik/src/sources/mod.rs	Added feature-gated pub use of CornSource and conditional pub(crate) mod corn_source;.
New Source Implementation confik/src/sources/corn_source.rs	Added CornSource<'a> with new() and allow_secrets(); implemented Source<T> (parsing via libcorn_0_10::from_str), Debug, and unit tests.
FileSource Extension confik/src/sources/file_source.rs	Added FileErrorKind::Corn (feature-gated); extended extension dispatch to parse .corn files when feature enabled; added feature-gated test.
Tests confik/tests/main.rs, confik/tests/secret/mod.rs	Added feature-gated tests verifying CORN parsing and secret-field rejection behavior.
Build Tooling justfile	Extended downgrade-for-msrv recipe to include additional cargo toolchain update commands for pest-related crates.

Sequence Diagram(s)

(omitted)

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• feat: RON support #379: Adds parallel feature-gated config source support (ron-0_12), with equivalent structural changes across Cargo.toml, lib.rs, sources/mod.rs, source implementations, and feature-gated tests.

Poem

🐰 In a meadow of bytes I scurry and spin,
A corn-string climbs in, and parsing begins.
With a hop and a nibble the config takes form,
Secrets stay guarded till you give them the norm.
Hooray for new sources — a crunchy new morn! 🌽

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: corn source' directly and clearly summarizes the main change: adding support for Corn as a configuration source.
Docstring Coverage	✅ Passed	Docstring coverage is 93.75% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ 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 corn-source

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[coderabbitai]

🧹 Nitpick comments (1)

confik/src/sources/corn_source.rs (1)

57-94: Tests provide good coverage; verbose trait syntax is correct but could be simplified.

The tests adequately cover parsing, error propagation, and secrets flag functionality. The fully-qualified trait method syntax (e.g., <CornSource<'_> as Source<...>>::provide(&source)) works correctly but could be simplified to Source::<...>::provide(&source) or just source.provide() since the trait is in scope.

🔧 Optional: Simplify test method calls

     #[test]
     fn provides_corn_data() {
         let source = CornSource::new("{ value = 42 }");
 
-        let config =
-            <CornSource<'_> as Source<<TestConfig as crate::Configuration>::Builder>>::provide(
-                &source,
-            )
+        let config = source
+            .provide()
             .unwrap()
             .try_build()
             .unwrap();
 
         assert_eq!(config, TestConfig { value: 42 });
     }

🤖 Prompt for AI Agents

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

In `@confik/src/sources/corn_source.rs` around lines 57 - 94, Tests use overly
verbose fully-qualified trait syntax when calling provide and allows_secrets;
simplify by calling the methods directly or with shorter turbofish forms.
Replace occurrences of `<CornSource<'_> as Source<<TestConfig as
crate::Configuration>::Builder>>::provide(&source)` with either
`source.provide()` or `Source::<TestConfig::Builder>::provide(&source)` and
similarly replace the long `allows_secrets` invocation with
`source.allows_secrets()` or
`Source::<TestConfig::Builder>::allows_secrets(&source)` while keeping the same
assertions; the relevant symbols are CornSource::new, provide, allows_secrets,
Source, and TestConfig.

🤖 Prompt for all review comments with AI agents

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

Nitpick comments:
In `@confik/src/sources/corn_source.rs`:
- Around line 57-94: Tests use overly verbose fully-qualified trait syntax when
calling provide and allows_secrets; simplify by calling the methods directly or
with shorter turbofish forms. Replace occurrences of `<CornSource<'_> as
Source<<TestConfig as crate::Configuration>::Builder>>::provide(&source)` with
either `source.provide()` or `Source::<TestConfig::Builder>::provide(&source)`
and similarly replace the long `allows_secrets` invocation with
`source.allows_secrets()` or
`Source::<TestConfig::Builder>::allows_secrets(&source)` while keeping the same
assertions; the relevant symbols are CornSource::new, provide, allows_secrets,
Source, and TestConfig.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yml

Review profile: CHILL

Plan: Pro

Run ID: d7f04ec7-f33b-4bbe-869e-6dd07f5d6c7f

📥 Commits

Reviewing files that changed from the base of the PR and between 1da667d and 9d6044e.

⛔ Files ignored due to path filters (1)

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

📒 Files selected for processing (10)

• confik/CHANGELOG.md
• confik/Cargo.toml
• confik/src/lib.md
• confik/src/lib.rs
• confik/src/sources/corn_source.rs
• confik/src/sources/file_source.rs
• confik/src/sources/mod.rs
• confik/tests/main.rs
• confik/tests/secret/mod.rs
• justfile

✅ Files skipped from review due to trivial changes (6)

• confik/CHANGELOG.md
• confik/src/sources/mod.rs
• confik/src/lib.md
• confik/tests/secret/mod.rs
• confik/tests/main.rs
• confik/Cargo.toml

🚧 Files skipped from review as they are similar to previous changes (1)

• confik/src/lib.rs