code-editing

name	code-editing
description	Use when writing, modifying, or removing Rust code in the mdvs codebase. Covers implementation workflow, testing, verification, and downstream updates (specs, example_kb, mdbook).

Code Editing Conventions

Before Writing Code

• Read the relevant existing code first. Explore patterns, naming conventions, module structure, and error handling style already in use.
• Match the existing style — don't introduce new patterns unless discussed with the user.
• If the change is non-trivial, plan it with the user before coding.

Writing Code

Style

• No wildcard imports (use arrow::array::* → explicit imports)
• Name intermediate data structures — no unnamed tuples or raw HashMaps
• From impls for infallible type conversions; constructors when extra parameters are needed
• Functions that don't use self should be free functions, not methods
• anyhow::Result for error handling in commands and I/O
• Follow the enum-based dispatch pattern (not traits) for runtime choices
• Never silently drop data — serialize to JSON rather than storing NULL
• Check for collisions with internal column prefix when adding new fields

Cross-cutting changes

If the change touches the type system, a violation type, a command's output, or storage format — trace through the full pipeline:

discover → schema/config → validation → storage → search → output

Verify each stage handles the change correctly.

Testing

• Write unit tests (#[cfg(test)] mod tests) for the changed module
• Write integration tests for user-facing behavior changes
• Run the full test suite, not just the changed module:

cargo test
cargo clippy
cargo fmt

Always run cargo fmt after cargo clippy.

Updating Specs

• Update the relevant spec in docs/spec/ if the change affects documented behavior
• Use the spec skill for spec writing conventions

Testing Against example_kb

• Run the affected commands against example_kb to verify the change works end-to-end
• If the change needs a new edge case, add it to example_kb:
  • Create or modify files to exercise the new behavior
  • Update example_kb/.plan.md with the new edge case
  • Re-run mdvs update example_kb and mdvs build example_kb --force

Updating the mdbook

• If the change affects any command output, re-run those commands and update the book pages with fresh output
• If the change adds new behavior, add a section to the relevant book page (use the book skill)
• Check for collateral effects — changes to example_kb may invalidate existing output examples across multiple pages
• Search the book for references to affected fields, commands, or concepts

TODOs

• If the work corresponds to a spec TODO, updating it to done is part of the commit workflow — see the commit skill