fix: core cache non working

Author: Luca Bianconi

Diff for: commands/compile/compile.go

@@ -66,8 +66,6 @@ func Compile(ctx context.Context, req *rpc.CompileRequest, outStream, errStream
 	if lm == nil {
 		return nil, &arduino.InvalidInstanceError{}
 	}
-	// cache is purged after compilation to not remove entries that might be required
-	defer maybePurgeBuildCache()
 
 	logrus.Tracef("Compile %s for %s started", req.GetSketchPath(), req.GetFqbn())
 	if req.GetSketchPath() == "" {
@@ -138,6 +136,11 @@ func Compile(ctx context.Context, req *rpc.CompileRequest, outStream, errStream
 	if err = builderCtx.BuildPath.MkdirAll(); err != nil {
 		return nil, &arduino.PermissionDeniedError{Message: tr("Cannot create build directory"), Cause: err}
 	}
+
+	buildcache.Used(builderCtx.BuildPath)
+	// cache is purged after compilation to not remove entries that might be required
+	defer maybePurgeBuildCache()
+
 	builderCtx.CompilationDatabase = bldr.NewCompilationDatabase(
 		builderCtx.BuildPath.Join("compile_commands.json"),
 	)
@@ -216,8 +219,6 @@ func Compile(ctx context.Context, req *rpc.CompileRequest, outStream, errStream
 		r.UsedLibraries = importedLibs
 	}()
 
-	defer buildcache.Used(builderCtx.BuildPath)
-
 	// if it's a regular build, go on...
 	if err := builder.RunBuilder(builderCtx); err != nil {
 		return r, &arduino.CompileFailedError{Message: err.Error()}

Diff for: legacy/builder/phases/core_builder.go

@@ -92,12 +92,10 @@ func compileCore(ctx *types.Context, buildPath *paths.Path, buildCachePath *path
 	realCoreFolder := coreFolder.Parent().Parent()
 
 	var targetArchivedCore *paths.Path
-	var targetArchivedCoreDir *paths.Path
 	if buildCachePath != nil {
 		archivedCoreName := GetCachedCoreArchiveDirName(buildProperties.Get(constants.BUILD_PROPERTIES_FQBN),
 			buildProperties.Get("compiler.optimization_flags"), realCoreFolder)
-		targetArchivedCoreDir = buildCachePath.Join(archivedCoreName)
-		targetArchivedCore = targetArchivedCoreDir.Join("core.a")
+		targetArchivedCore = buildCachePath.Join(archivedCoreName).Join("core.a")
 		canUseArchivedCore := !ctx.OnlyUpdateCompilationDatabase &&
 			!ctx.Clean &&
 			!builder_utils.CoreOrReferencedCoreHasChanged(realCoreFolder, targetCoreFolder, targetArchivedCore)
@@ -123,9 +121,9 @@ func compileCore(ctx *types.Context, buildPath *paths.Path, buildCachePath *path
 
 	// archive core.a
 	if targetArchivedCore != nil && !ctx.OnlyUpdateCompilationDatabase {
-		defer buildcache.Used(targetArchivedCore)
-		targetArchivedCoreDir.MkdirAll()
+		targetArchivedCore.Parent().MkdirAll()
 		err := archiveFile.CopyTo(targetArchivedCore)
+		buildcache.Used(targetArchivedCore.Parent())
 		if ctx.Verbose {
 			if err == nil {
 				ctx.Info(tr("Archiving built core (caching) in: %[1]s", targetArchivedCore))

Diff for: legacy/builder/test/builder_test.go

@@ -384,6 +384,9 @@ func TestBuilderCacheCoreAFile(t *testing.T) {
 	cachedCoreFile := ctx.CoreBuildCachePath.Join(coreFileName, "core.a")
 	coreStatBefore, err := cachedCoreFile.Stat()
 	require.NoError(t, err)
+	lastUsedFile := ctx.CoreBuildCachePath.Join(coreFileName, ".last-used")
+	_, err = lastUsedFile.Stat()
+	require.NoError(t, err)
 
 	// Run build again, to verify that the builder skips rebuilding core.a
 	err = bldr.Run(ctx)