[clang-tools-extra] [clang-tidy] filter check options by enabled checks in '--dump-config' (PR #147142)

[Baranov Victor via cfe-commits]

https://github.com/vbvictor created https://github.com/llvm/llvm-project/pull/147142

Added function to filter out options that come from `ClangTidyOptions::getDefaults()`, but does not have a corresponding check enabled in the configuration.

Fixes https://github.com/llvm/llvm-project/issues/146693.

>From d70b792ece6709b7a68baf116c0895394c71fd16 Mon Sep 17 00:00:00 2001
From: Victor Baranov <bar.victor.2002 at gmail.com>
Date: Sat, 5 Jul 2025 15:12:04 +0300
Subject: [PATCH] [clang-tidy] filter check options by enabled checks in
 '--dump-config'

---
 clang-tools-extra/clang-tidy/ClangTidy.cpp        | 15 +++++++++++++++
 clang-tools-extra/clang-tidy/ClangTidy.h          |  5 +++++
 .../clang-tidy/tool/ClangTidyMain.cpp             |  7 ++++---
 clang-tools-extra/docs/ReleaseNotes.rst           |  3 +++
 .../infrastructure/dump-config-filtering.cpp      | 12 ++++++++++++
 5 files changed, 39 insertions(+), 3 deletions(-)
 create mode 100644 clang-tools-extra/test/clang-tidy/infrastructure/dump-config-filtering.cpp

diff --git a/clang-tools-extra/clang-tidy/ClangTidy.cpp b/clang-tools-extra/clang-tidy/ClangTidy.cpp
index f4ab93b51f4a7..30bc96d62de7c 100644
--- a/clang-tools-extra/clang-tidy/ClangTidy.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidy.cpp
@@ -503,6 +503,21 @@ getCheckNames(const ClangTidyOptions &Options,
   return Factory.getCheckNames();
 }
 
+void filterCheckOptions(ClangTidyOptions &Options,
+                        const std::vector<std::string> &EnabledChecks) {
+  StringSet<> EnabledChecksSet(llvm::from_range, EnabledChecks);
+  ClangTidyOptions::OptionMap FilteredOptions;
+  for (const auto &[OptionName, Value] : Options.CheckOptions) {
+    const size_t CheckNameEndPos = OptionName.find('.');
+    if (CheckNameEndPos == StringRef::npos)
+      continue;
+    const StringRef CheckName = OptionName.substr(0, CheckNameEndPos);
+    if (EnabledChecksSet.contains(CheckName))
+      FilteredOptions[OptionName] = Value;
+  }
+  Options.CheckOptions = std::move(FilteredOptions);
+}
+
 ClangTidyOptions::OptionMap
 getCheckOptions(const ClangTidyOptions &Options,
                 bool AllowEnablingAnalyzerAlphaCheckers) {
diff --git a/clang-tools-extra/clang-tidy/ClangTidy.h b/clang-tools-extra/clang-tidy/ClangTidy.h
index 4ffd49f6ebf50..02ab3a0c1d213 100644
--- a/clang-tools-extra/clang-tidy/ClangTidy.h
+++ b/clang-tools-extra/clang-tidy/ClangTidy.h
@@ -76,6 +76,11 @@ ClangTidyOptions::OptionMap
 getCheckOptions(const ClangTidyOptions &Options,
                 bool AllowEnablingAnalyzerAlphaCheckers);
 
+/// Filters CheckOptions in \p Options to only include options specified in
+/// the \p EnabledChecks.
+void filterCheckOptions(ClangTidyOptions &Options,
+                        const std::vector<std::string> &EnabledChecks);
+
 /// Run a set of clang-tidy checks on a set of files.
 ///
 /// \param EnableCheckProfile If provided, it enables check profile collection
diff --git a/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp b/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
index 4336c723bd7cd..4de1caec5ec8c 100644
--- a/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
+++ b/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
@@ -659,9 +659,10 @@ int clangTidyMain(int argc, const char **argv) {
   if (DumpConfig) {
     EffectiveOptions.CheckOptions =
         getCheckOptions(EffectiveOptions, AllowEnablingAnalyzerAlphaCheckers);
-    llvm::outs() << configurationAsText(ClangTidyOptions::getDefaults().merge(
-                        EffectiveOptions, 0))
-                 << "\n";
+    ClangTidyOptions OptionsToDump =
+        ClangTidyOptions::getDefaults().merge(EffectiveOptions, 0);
+    filterCheckOptions(OptionsToDump, EnabledChecks);
+    llvm::outs() << configurationAsText(OptionsToDump) << "\n";
     return 0;
   }
 
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 198efee7754de..c8f9c127c115c 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -108,6 +108,9 @@ Improvements to clang-tidy
 - Improved :program:`clang-tidy-diff.py` script. Add the `-warnings-as-errors`
   argument to treat warnings as errors.
 
+- Improved :program:`clang-tidy` to show `CheckOptions` only for checks enabled
+  in `Checks` when running ``--dump-config``.
+
 - Fixed bug in :program:`clang-tidy` by which `HeaderFilterRegex` did not take
   effect when passed via the `.clang-tidy` file.
 
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/dump-config-filtering.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/dump-config-filtering.cpp
new file mode 100644
index 0000000000000..f22ec7edb1775
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/dump-config-filtering.cpp
@@ -0,0 +1,12 @@
+// RUN: clang-tidy -checks='-*,misc-unused-parameters' -dump-config %s -- 2>/dev/null | FileCheck %s --check-prefix=CHECK
+// RUN: clang-tidy -checks='-*' -dump-config %s -- 2>/dev/null | FileCheck %s --check-prefix=CHECK-DISABLED
+
+// CHECK: CheckOptions:
+// CHECK-NEXT:   misc-unused-parameters.IgnoreVirtual: 'false'
+// CHECK-NEXT:   misc-unused-parameters.StrictMode: 'false'
+// CHECK-NEXT: SystemHeaders:   false
+
+// CHECK-DISABLED: CheckOptions:    {}
+// CHECK-DISABLED-NEXT: SystemHeaders:   false
+
+int main() { return 0; }