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CloudflareKnown publishercloudflare/workerd/.opencode/skills/iwyu/SKILL.md

iwyu

Skill9k starsChanged 8 months agoApache-2.0View on GitHub

Follow IWYU guidelines to improve build caching. This entails adding/removing C++

We split this skill into the rules it gives an agent

5 rules. About 0 are common, 1 is distinctive, and 4 are very specific to this project.

  • ≈0

    Common · estimate

    Many files like this have a rule of this kind.

  • ≈1

    Distinctive · estimate

    This author's own choices. Worth a look.

  • 4

    Very specific

    Tied to their project's names, files or tools. Probably skip.

  • Common
  • Distinctive
  • Very specific
  1. Very specific:

    Don't add #includes a file doesn't use or deps a target doesn't use.

    line 13
  2. Very specific:

    Put deps whose headers are included only from .c++ files in implementation_deps, so they don't propagate to dependents.

    line 15
  3. Distinctive:

    Prefer direct includes and deps over relying on transitive ones, but don't add a long list just to spell out what you already get …

    line 17
  4. Very specific:

    Keep each header in exactly one target, together with its .c++ if it has one.

    line 25
  5. Very specific:

    If splitting a pair out would create a dependency cycle, leave it in its combined target (e.g.

    line 28

≈ “Common” is an estimate: at least 1 in 5 of the 308,232 skill files we read have a rule of the same kind, not the same words. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.

Keep what fits and drop the rest. Your version, ready for your agents.
Files
SKILL.md

IWYU FOR C++ TARGETS

Adapted from include-what-you-use. Small targets with accurate deps mean a change rebuilds and retests fewer targets.

  • Don't add #includes a file doesn't use or deps a target doesn't use. When a change removes the last use of a header, delete its #include, then the dep if it's now unused.
  • Put deps whose headers are included only from .c++ files in implementation_deps, so they don't propagate to dependents.
  • Prefer direct includes and deps over relying on transitive ones, but don't add a long list just to spell out what you already get transitively. For instance, most workerd C++ sources depend on KJ but we don't declare this dependency for each target separately, or include kj/common.h, kj/string.h and so on each time. Direct includes that are already present and being used should generally stay in place.
  • Give each .h/.c++ pair its own wd_cc_library, named after the file (e.g. :tracked-wasm-instance). A header without a .c++ gets its own target too, with the deps it needs to compile on its own.
  • Keep each header in exactly one target, together with its .c++ if it has one. Exposing a header from a target that doesn't build its .c++ lets code call its functions without depending on their definitions, which shows up later as undefined-symbol link errors.
  • If splitting a pair out would create a dependency cycle, leave it in its combined target (e.g. //src/workerd/io) instead of separating the header from its .c++. Don't add new files to such targets if they can have their own.

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