57 lines
1.9 KiB
Markdown
57 lines
1.9 KiB
Markdown
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# Clang tidy lints for Nix
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This is a skeleton of a clang-tidy lints library for Nix.
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Currently there is one check (which is already obsolete as it has served its
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goal and is there as an example), `HasPrefixSuffixCheck`.
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## Running fixes/checks
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One file:
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```
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ninja -C build && clang-tidy --checks='-*,nix-*' --load=build/libnix-clang-tidy.so -p ../compile_commands.json --fix ../src/libcmd/installables.cc
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```
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Several files, in parallel:
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```
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ninja -C build && run-clang-tidy -checks='-*,nix-*' -load=build/libnix-clang-tidy.so -p .. -fix ../src | tee -a clang-tidy-result
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```
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## Resources
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* https://firefox-source-docs.mozilla.org/code-quality/static-analysis/writing-new/clang-query.html
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* https://clang.llvm.org/docs/LibASTMatchersReference.html
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* https://devblogs.microsoft.com/cppblog/exploring-clang-tooling-part-3-rewriting-code-with-clang-tidy/
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## Developing new checks
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Put something like so in `myquery.txt`:
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```
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set traversal IgnoreUnlessSpelledInSource
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# ^ Ignore implicit AST nodes. May need to use AsIs depending on how you are
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# working.
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set bind-root true
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# ^ true unless you use any .bind("foo") commands
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set print-matcher true
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enable output dump
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match callExpr(callee(functionDecl(hasName("hasPrefix"))), optionally(hasArgument( 0, cxxConstructExpr(hasDeclaration(functionDecl(hasParameter(0, parmVarDecl(hasType(asString("const char *"))).bind("meow2"))))))))
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```
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Then run, e.g. `clang-query --preload hasprefix.query -p compile_commands.json src/libcmd/installables.cc`.
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With this you can iterate a query before writing it in C++ and suffering from
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C++.
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### Tips and tricks for the C++
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There is a function `dump()` on many things that will dump to stderr. Also
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`llvm::errs()` lets you print to stderr.
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When I wrote `HasPrefixSuffixCheck`, I was not really able to figure out how
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the structured replacement system was supposed to work. In principle you can
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describe the replacement with a nice DSL. Look up the Stencil system in Clang
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for details.
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