Diagnostics: Fix order in which presets are applied

Rewrite the function that updates the diagnostic state from presets to
apply all modifications concurrently. Previously, we applied all
warnings, then all errors, which (because changes are recursive) could
result in an enabled error for a parent diagnostic overriding a disabled
warning for a child diagnostic.

Source/cmake.cxx

@@ -496,23 +496,29 @@ void cmake::SetDiagnosticsFromPreset(
   std::map<cmDiagnosticCategory, bool> const& warnings,
   std::map<cmDiagnosticCategory, bool> const& errors)
 {
-  for (auto const& wi : warnings) {
-    if (wi.second) {
-      this->CurrentSnapshot.PromoteDiagnostic( // clang-format: break
-        wi.first, cmDiagnostics::Warn, true);
-    } else {
-      this->CurrentSnapshot.DemoteDiagnostic( // clang-format: break
-        wi.first, cmDiagnostics::Ignore, true);
-    }
-  }
+  for (unsigned i = 1; i < cmDiagnostics::CategoryCount; ++i) {
+    auto const category = static_cast<cmDiagnosticCategory>(i);
 
-  for (auto const& ei : errors) {
-    if (ei.second) {
-      this->CurrentSnapshot.PromoteDiagnostic( // clang-format: break
-        ei.first, cmDiagnostics::SendError, true);
-    } else {
-      this->CurrentSnapshot.DemoteDiagnostic( // clang-format: break
-        ei.first, cmDiagnostics::Warn, true);
+    auto const wi = warnings.find(category);
+    if (wi != warnings.end()) {
+      if (wi->second) {
+        this->CurrentSnapshot.PromoteDiagnostic( // clang-format: break
+          category, cmDiagnostics::Warn, true);
+      } else {
+        this->CurrentSnapshot.DemoteDiagnostic( // clang-format: break
+          category, cmDiagnostics::Ignore, true);
+      }
+    }
+
+    auto const ei = errors.find(category);
+    if (ei != errors.end()) {
+      if (ei->second) {
+        this->CurrentSnapshot.PromoteDiagnostic( // clang-format: break
+          category, cmDiagnostics::SendError, true);
+      } else {
+        this->CurrentSnapshot.DemoteDiagnostic( // clang-format: break
+          category, cmDiagnostics::Warn, true);
+      }
     }
   }
 }

Tests/RunCMake/CMakePresets/DiagnosticOrder.cmake

@@ -0,0 +1,6 @@
+cmake_diagnostic(GET CMD_DEPRECATED action)
+if(NOT "${action}" STREQUAL IGNORE)
+   message(SEND_ERROR
+     "wrong action for diagnostic CMD_DEPRECATED"
+     " (expected 'IGNORE', actual '${action}')")
+endif()

Tests/RunCMake/CMakePresets/RunCMakeTest.cmake

@@ -365,6 +365,7 @@ run_cmake_presets(DisableWarningFlags)
 run_cmake_presets(ErrorDev)
 run_cmake_presets(ErrorUninitialized)
 run_cmake_presets(ErrorUnusedCli)
+run_cmake_presets(DiagnosticOrder)
 unset(CMakePresets_WARN_UNUSED_CLI)
 
 # Test debug

Tests/RunCMake/CMakePresets/Warnings12.json.in

@@ -65,6 +65,17 @@
       "errors": {
         "unusedCli": true
       }
+    },
+    {
+      "name": "DiagnosticOrder",
+      "inherits": "NoWarningFlags",
+      "warnings": {
+        "deprecated": false,
+        "unusedCli": false
+      },
+      "errors": {
+        "author": true
+      }
     }
   ]
 }