Allow use of a dependency helper source file during library detection

internal/arduino/builder/internal/detector/detector.go

@@ -414,9 +414,14 @@ func (l *SketchLibrariesDetector) findIncludesUntilDone(
 				l.logger.Info(i18n.Tr("Skipping dependencies detection for precompiled library %[1]s", library.Name))
 			}
 		} else {
-			for _, sourceDir := range library.SourceDirs() {
-				l.queueSourceFilesFromFolder(sourceFileQueue, sourceDir.Dir, sourceDir.Recurse,
+			if helperSource := library.DependencyHelper(); helperSource != nil {
+				l.queueSourceFile(sourceFileQueue, helperSource,
 					library.SourceDir, librariesBuildPath.Join(library.DirName), library.UtilityDir)
+			} else {
+				for _, sourceDir := range library.SourceDirs() {
+					l.queueSourceFilesFromFolder(sourceFileQueue, sourceDir.Dir, sourceDir.Recurse,
+						library.SourceDir, librariesBuildPath.Join(library.DirName), library.UtilityDir)
+				}
 			}
 		}
 		first = false
@@ -441,16 +446,29 @@ func (l *SketchLibrariesDetector) queueSourceFilesFromFolder(
 	}
 
 	for _, filePath := range filePaths {
-		sourceFile, err := makeSourceFile(sourceDir, buildDir, filePath, extraIncludePath...)
-		if err != nil {
+		if err := l.queueSourceFile(sourceFileQueue, filePath, sourceDir, buildDir, extraIncludePath...); err != nil {
 			return err
 		}
-		sourceFileQueue.push(sourceFile)
 	}
 
 	return nil
 }
 
+func (l *SketchLibrariesDetector) queueSourceFile(
+	sourceFileQueue *uniqueSourceFileQueue,
+	filePath *paths.Path,
+	sourceDir *paths.Path,
+	buildDir *paths.Path,
+	extraIncludePath ...*paths.Path,
+) error {
+	sourceFile, err := makeSourceFile(sourceDir, buildDir, filePath, extraIncludePath...)
+	if err != nil {
+		return err
+	}
+	sourceFileQueue.push(sourceFile)
+	return nil
+}
+
 func (l *SketchLibrariesDetector) failIfImportedLibraryIsWrong() error {
 	if len(l.importedLibraries) == 0 {
 		return nil

internal/arduino/libraries/libraries.go

@@ -239,3 +239,14 @@ func (library *Library) SourceHeaders() ([]string, error) {
 	}
 	return library.sourceHeaders, nil
 }
+
+// DependencyHelper returns the path to the dependency helper file.
+func (library *Library) DependencyHelper() *paths.Path {
+	if c := library.SourceDir.Join("arduino_deps.c"); c.Exist() {
+		return c
+	}
+	if cpp := library.SourceDir.Join("arduino_deps.cpp"); cpp.Exist() {
+		return cpp
+	}
+	return nil
+}