Stop UTILITY targets from breaking IntelliSense (#4404)

CHANGELOG.md

@@ -33,6 +33,7 @@ Bug Fixes:
 - Fix bug that makes some build hang [#4424](https://github.com/microsoft/vscode-cmake-tools/issues/4424) and [#4465](https://github.com/microsoft/vscode-cmake-tools/issues/4465)
 - Fix issue with switching to presets during Quick Start. [#4409](https://github.com/microsoft/vscode-cmake-tools/issues/4409)
 - Fix bug that shows empty lines in Pinned Commands view. [#4406](https://github.com/microsoft/vscode-cmake-tools/issues/4406)
+- Fix incorrect IntelliSense configuration when a `UTILITY` has source files. [#4404](https://github.com/microsoft/vscode-cmake-tools/issues/4404)
 
 ## 1.20.53
 

src/cpptools.ts

@@ -310,6 +310,27 @@ export function getIntelliSenseMode(cptVersion: cpptools.Version, compilerPath:
     }
 }
 
+/**
+ * Try to find a target configuration with some populated properties.
+ *
+ * All targets get defaults for `compilerPath`, `compilerArgs`, and
+ * `compilerFragments`, even `UTILITY` targets defined with
+ * `add_custom_command()` that provide no other useful configuration, so if
+ * possible, return one with more than just those populated.
+ */
+function fallbackConfiguration(configurations: Map<string, cpptools.SourceFileConfigurationItem> | undefined) {
+    if (!configurations) {
+        return undefined;
+    }
+    for (const item of configurations.values()) {
+        const { configuration: { includePath, defines, intelliSenseMode, standard} } = item;
+        if (includePath.length || defines.length || intelliSenseMode || standard) {
+            return item;
+        }
+    }
+    return configurations.values().next().value;
+}
+
 /**
  * The actual class that provides information to the cpptools extension. See
  * the `CustomConfigurationProvider` interface for information on how this class
@@ -345,7 +366,7 @@ export class CppConfigurationProvider implements cpptools.CustomConfigurationPro
         if (this.activeTarget && configurations?.has(this.activeTarget)) {
             return configurations!.get(this.activeTarget);
         } else {
-            return configurations?.values().next().value; // Any value is fine if the target doesn't match
+            return fallbackConfiguration(configurations);
         }
     }
 

test/unit-tests/cpptools.test.ts

@@ -321,12 +321,21 @@ suite('CppTools tests', () => {
                     name: 'cpptools-test2',
                     sourceDirectory: smokeFolder,
                     targets: [
+                        {
+                            name: 'utilityTarget',
+                            type: 'UTILITY',
+                            fileGroups: [{
+                                sources: [sourceFile3],
+                                isGenerated: false
+                            }]
+                        },
                         {
                             name: 'target3',
                             type: 'EXECUTABLE',
                             fileGroups: [{
                                 sources: [sourceFile3],
                                 isGenerated: false,
+                                defines: ['DEFINE3'], // make this a more attractive fallback than utilityTarget
                                 compileCommandFragments: ['-DFRAGMENT3'],
                                 language: 'CXX'
                             }]
@@ -370,7 +379,8 @@ suite('CppTools tests', () => {
         // Verify the browsePath with a different folder.
         const configurations2 = await provider.provideConfigurations([uri3]);
         expect(configurations2.length).to.eq(1);
-        expect(configurations2[0].configuration.defines).to.be.empty;
+        expect(configurations2[0].configuration.defines.length).to.eq(1);
+        expect(configurations2[0].configuration.defines).to.contain('DEFINE3');
         expect(configurations2[0].configuration.compilerFragments).to.contain('-DFRAGMENT3');
         const browseConfig2 = await provider.provideFolderBrowseConfiguration(vscode.Uri.file(smokeFolder));
         expect(browseConfig2?.browsePath.length).to.eq(1);