clang-tidy check infrastructure

This brings in infrastructure for developing new custom clang-tidy lints
and refactors for Lix.

Change-Id: I3df5f5855712ab4f97d4e84d771e5e818f81f881
This commit is contained in:
jade 2024-03-17 19:54:58 -07:00
parent 61e21b2557
commit 6b0020749d
7 changed files with 195 additions and 1 deletions

1
clang-tidy/.clang-format Normal file
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BasedOnStyle: llvm

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#include "HasPrefixSuffix.hh"
#include <clang/AST/ASTTypeTraits.h>
#include <clang/AST/Expr.h>
#include <clang/AST/PrettyPrinter.h>
#include <clang/AST/Type.h>
#include <clang/ASTMatchers/ASTMatchers.h>
#include <clang/Basic/Diagnostic.h>
#include <clang/Frontend/FrontendAction.h>
#include <clang/Frontend/FrontendPluginRegistry.h>
#include <clang/Tooling/Transformer/SourceCode.h>
#include <clang/Tooling/Transformer/SourceCodeBuilders.h>
#include <iostream>
namespace nix::clang_tidy {
using namespace clang::ast_matchers;
using namespace clang;
void HasPrefixSuffixCheck::registerMatchers(ast_matchers::MatchFinder *Finder) {
Finder->addMatcher(
traverse(clang::TK_AsIs,
callExpr(callee(functionDecl(anyOf(hasName("hasPrefix"),
hasName("hasSuffix")))
.bind("callee-decl")),
optionally(hasArgument(
0, cxxConstructExpr(
hasDeclaration(functionDecl(hasParameter(
0, parmVarDecl(hasType(
asString("const char *")))))))
.bind("implicit-cast"))))
.bind("call")),
this);
}
void HasPrefixSuffixCheck::check(
const ast_matchers::MatchFinder::MatchResult &Result) {
const auto *CalleeDecl = Result.Nodes.getNodeAs<FunctionDecl>("callee-decl");
auto FuncName = std::string(CalleeDecl->getName());
std::string NewName;
if (FuncName == "hasPrefix") {
NewName = "starts_with";
} else if (FuncName == "hasSuffix") {
NewName = "ends_with";
} else {
llvm_unreachable("nix-has-prefix: invalid callee");
}
const auto *MatchedDecl = Result.Nodes.getNodeAs<CallExpr>("call");
const auto *ImplicitConvertArg =
Result.Nodes.getNodeAs<CXXConstructExpr>("implicit-cast");
const auto *Lhs = MatchedDecl->getArg(0);
const auto *Rhs = MatchedDecl->getArg(1);
auto Diag = diag(MatchedDecl->getExprLoc(), FuncName + " is deprecated");
std::string Text = "";
// Form possible cast to string_view, or nothing.
if (ImplicitConvertArg) {
Text = "std::string_view(";
Text.append(tooling::getText(*Lhs, *Result.Context));
Text.append(").");
} else {
Text.append(*tooling::buildAccess(*Lhs, *Result.Context));
}
// Call .starts_with.
Text.append(NewName);
Text.push_back('(');
Text.append(tooling::getText(*Rhs, *Result.Context));
Text.push_back(')');
Diag << FixItHint::CreateReplacement(MatchedDecl->getSourceRange(), Text);
// for (const auto *arg : MatchedDecl->arguments()) {
// arg->dumpColor();
// arg->getType().dump();
// }
}
}; // namespace nix::clang_tidy

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#pragma once
///@file
/// This is an example of a clang-tidy automated refactoring against the Nix
/// codebase. The refactoring has been completed in
/// https://gerrit.lix.systems/c/lix/+/565 so this code is around as
/// an example.
#include <clang-tidy/ClangTidyCheck.h>
#include <clang/ASTMatchers/ASTMatchFinder.h>
#include <llvm/ADT/StringRef.h>
namespace nix::clang_tidy {
using namespace clang;
using namespace clang::tidy;
using namespace llvm;
class HasPrefixSuffixCheck : public ClangTidyCheck {
public:
HasPrefixSuffixCheck(StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context) {}
void registerMatchers(ast_matchers::MatchFinder *Finder) override;
void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
};
}; // namespace nix::clang_tidy

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#include <clang-tidy/ClangTidyModule.h>
#include <clang-tidy/ClangTidyModuleRegistry.h>
#include "HasPrefixSuffix.hh"
namespace nix::clang_tidy {
using namespace clang;
using namespace clang::tidy;
class NixClangTidyChecks : public ClangTidyModule {
public:
void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
CheckFactories.registerCheck<HasPrefixSuffixCheck>("nix-hasprefixsuffix");
}
};
static ClangTidyModuleRegistry::Add<NixClangTidyChecks> X("nix-module", "Adds nix specific checks");
};

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

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project('nix-clang-tidy', ['cpp', 'c'],
version : '0.1',
default_options : ['warning_level=3', 'cpp_std=c++20'])
llvm = dependency('Clang', version: '>= 14', modules: ['libclang'])
sources = ['HasPrefixSuffix.cc', 'NixClangTidyChecks.cc']
shared_module('nix-clang-tidy', sources,
dependencies: llvm)

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}; };
in in
nix.overrideAttrs (prev: { nix.overrideAttrs (prev: {
# Required for clang-tidy checks
buildInputs = prev.buildInputs ++ lib.optionals (stdenv.cc.isClang) [ pkgs.llvmPackages.llvm pkgs.llvmPackages.clang-unwrapped.dev ];
nativeBuildInputs = prev.nativeBuildInputs nativeBuildInputs = prev.nativeBuildInputs
++ lib.optional (stdenv.cc.isClang && !stdenv.buildPlatform.isDarwin) pkgs.buildPackages.bear ++ lib.optional (stdenv.cc.isClang && !stdenv.buildPlatform.isDarwin) pkgs.buildPackages.bear
# Required for clang-tidy checks
++ lib.optionals (stdenv.cc.isClang) [ pkgs.buildPackages.cmake pkgs.buildPackages.ninja pkgs.buildPackages.llvmPackages.llvm.dev ]
++ lib.optional ++ lib.optional
(stdenv.cc.isClang && stdenv.hostPlatform == stdenv.buildPlatform) (stdenv.cc.isClang && stdenv.hostPlatform == stdenv.buildPlatform)
pkgs.buildPackages.clang-tools; # for some reason that seems accidental and was changed in
# NixOS 24.05-pre, clang-tools is pinned to LLVM 14 when
# default LLVM is newer.
(pkgs.buildPackages.clang-tools.override { inherit (pkgs.buildPackages) llvmPackages; });
src = null; src = null;