From b918f1c307b314daa44407bac60046630f13ed48 Mon Sep 17 00:00:00 2001
From: eldritch horrors <pennae@lix.systems>
Date: Wed, 26 Mar 2025 19:26:02 +0100
Subject: [PATCH] tidy: add a lint to forbid nlohmann::json::parse

Change-Id: I165c7330d7ea7f17522ade8a0666d0d7d86b9d38
---
 lix/libutil/json.hh                           |  1 +
 subprojects/lix-clang-tidy/DisallowedDecls.cc | 37 +++++++++++++++++++
 subprojects/lix-clang-tidy/DisallowedDecls.hh | 21 +++++++++++
 .../lix-clang-tidy/LixClangTidyChecks.cc      |  2 +
 subprojects/lix-clang-tidy/meson.build        |  1 +
 5 files changed, 62 insertions(+)
 create mode 100644 subprojects/lix-clang-tidy/DisallowedDecls.cc
 create mode 100644 subprojects/lix-clang-tidy/DisallowedDecls.hh

diff --git a/lix/libutil/json.hh b/lix/libutil/json.hh
index 3d1a2a5ae..d30e38df6 100644
--- a/lix/libutil/json.hh
+++ b/lix/libutil/json.hh
@@ -163,6 +163,7 @@ template<typename Source>
 JSON parse(Source && source, std::optional<std::string_view> context = {})
 {
     try {
+        // NOLINTNEXTLINE(lix-disallowed-decls): this is the wrapper for that
         return JSON::parse(std::forward<Source>(source));
     } catch (JSON::exception & e) {
         ParseError error{"failed to parse JSON: %s", e.what()};
diff --git a/subprojects/lix-clang-tidy/DisallowedDecls.cc b/subprojects/lix-clang-tidy/DisallowedDecls.cc
new file mode 100644
index 000000000..41c735c9e
--- /dev/null
+++ b/subprojects/lix-clang-tidy/DisallowedDecls.cc
@@ -0,0 +1,37 @@
+#include "DisallowedDecls.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>
+
+namespace nix::clang_tidy {
+using namespace clang::ast_matchers;
+using namespace clang;
+
+void DisallowedDeclsCheck::registerMatchers(ast_matchers::MatchFinder *Finder) {
+  Finder->addMatcher(
+      traverse(clang::TK_AsIs,
+               callExpr(callee(cxxMethodDecl(hasName("parse"),
+                                             ofClass(isSameOrDerivedFrom(
+                                                 "nlohmann::basic_json")))))
+                   .bind("json-parse")),
+      this);
+}
+
+void DisallowedDeclsCheck::check(
+    const ast_matchers::MatchFinder::MatchResult &Result) {
+
+  if (auto MatchedParse = Result.Nodes.getNodeAs<CallExpr>("json-parse")) {
+    auto Diag = diag(MatchedParse->getExprLoc(),
+                     "using nlohmann::basic_json::parse is disallowed, use the lix wrapper instead");
+    Diag << FixItHint::CreateReplacement(MatchedParse->getCallee()->getSourceRange(),
+                                       "json::parse");
+  }
+}
+}; // namespace nix::clang_tidy
diff --git a/subprojects/lix-clang-tidy/DisallowedDecls.hh b/subprojects/lix-clang-tidy/DisallowedDecls.hh
new file mode 100644
index 000000000..c4c5659e1
--- /dev/null
+++ b/subprojects/lix-clang-tidy/DisallowedDecls.hh
@@ -0,0 +1,21 @@
+#pragma once
+///@file
+
+#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 DisallowedDeclsCheck : public ClangTidyCheck {
+public:
+  DisallowedDeclsCheck(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
diff --git a/subprojects/lix-clang-tidy/LixClangTidyChecks.cc b/subprojects/lix-clang-tidy/LixClangTidyChecks.cc
index 4bcd5bc89..62da97f2f 100644
--- a/subprojects/lix-clang-tidy/LixClangTidyChecks.cc
+++ b/subprojects/lix-clang-tidy/LixClangTidyChecks.cc
@@ -1,5 +1,6 @@
 #include <clang-tidy/ClangTidyModule.h>
 #include <clang-tidy/ClangTidyModuleRegistry.h>
+#include "DisallowedDecls.hh"
 #include "HasPrefixSuffix.hh"
 #include "CharPtrCast.hh"
 #include "NeverAsync.hh"
@@ -14,6 +15,7 @@ class NixClangTidyChecks : public ClangTidyModule {
             CheckFactories.registerCheck<HasPrefixSuffixCheck>("lix-hasprefixsuffix");
             CheckFactories.registerCheck<CharPtrCastCheck>("lix-charptrcast");
             CheckFactories.registerCheck<NeverAsync>("lix-never-async");
+            CheckFactories.registerCheck<DisallowedDeclsCheck>("lix-disallowed-decls");
         }
 };
 
diff --git a/subprojects/lix-clang-tidy/meson.build b/subprojects/lix-clang-tidy/meson.build
index 7b5948369..174880ca4 100644
--- a/subprojects/lix-clang-tidy/meson.build
+++ b/subprojects/lix-clang-tidy/meson.build
@@ -6,6 +6,7 @@ project('lix-clang-tidy', ['cpp', 'c'],
 llvm = dependency('Clang', version: '>= 16', modules: ['libclang'])
 sources = files(
   'CharPtrCast.cc',
+  'DisallowedDecls.cc',
   'HasPrefixSuffix.cc',
   'LixClangTidyChecks.cc',
   'NeverAsync.cc',