[Design] Obey conditions in #[cfg(..)] and #[cfg_attr(..)]#623
[Design] Obey conditions in #[cfg(..)] and #[cfg_attr(..)]#623sandersaares wants to merge 2 commits into
#[cfg(..)] and #[cfg_attr(..)]#623Conversation
Introduces design/obey-cfg.md describing a multi-phase pipeline (Candidate collection -> probe -> filter) for evaluating #[cfg(..)] and #[cfg_attr(..)] attributes via the Rust toolchain itself, rather than reimplementing cfg evaluation. Status: Draft. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
There was a problem hiding this comment.
Pull request overview
Adds a draft design document describing how cargo-mutants could start honoring conditional compilation (#[cfg(...)] / #[cfg_attr(...)]) by collecting cfg conditions during discovery, probing the active toolchain/cargo invocation to evaluate those conditions, and filtering candidates before producing mutants. This is intended to address issue #50 by avoiding mutants in cfg-dead code and by only honoring mutants::* attributes inside cfg_attr when their predicate is true.
Changes:
- Add a detailed design proposal for a 3-phase pipeline: collect conditional candidates → probe toolchain for cfg truth values → filter to live mutants.
- Specify a per-package probing mechanism implemented as an auto-generated integration test (
tests/__cargo_mutants_probe.rs) executed with the same cargo flags/profile used for mutation testing. - Define proposed CLI/config surface (
--ignore-cfg/ignore_cfg = true) and document edge cases/limitations (e.g., conditional#[path]non-goal).
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
sandersaares
changed the title
#[cfg(..)] and #[cfg_attr(..)]#[cfg(..)] and #[cfg_attr(..)]
- is_live pseudocode: use get(...).unwrap_or(...) so unknown CfgExprs fall back conservatively to keep candidates live, per the rule in 5.4/6.3 (avoids a HashMap-indexing panic that would contradict the spec). - Prerequisite bullet: reword to describe the prerequisite change to DiscoveryVisitor (exclude-re-attr scope stack) instead of linking the word 'branch' to src/visit.rs, which was confusing. - Phase-B flow diagram: replace the stray 'CMP|cNNNN|0|1' with the 'CMP|<id>|<0|1>' template that matches the 5.4 protocol (three pipe-separated fields, not four). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
|
Hey I appreciate the thought and I would like to add this feature. But I also think that reviewing 1000 line AI-generated docs and PRs is going to make this spare-time passion project much less enjoyable and motivating for me. Obviously we all have a lot to work through to understand what it means to do open source in the era of agentic coding. |
|
Sure, feel free to engage or not-engage with the topic to the level of your comfort. What do you suggest as a useful course to get such features into the tool? |
Today, the app does not understand the conditions
#[cfg(..)]and#[cfg_attr(..)], always treating the conditions as true. This is a proposed design for fixing that (#50).Opening PR to discuss design before any implementation work.
@sourcefrog WDYT?