bugfix: mount build cache directories (dirs were not created at host-side)

Author: joonas-fi

cmd/bob/build.go

@@ -75,7 +75,10 @@ func runBuilder(builder bobfile.BuilderSpec, buildCtx *BuildContext, opDesc stri
 	baseImageConf, err := loadNonOptionalBaseImageConf(buildCtx.Bobfile.ProjectName, builder)
 	if err == nil { // it's optional here. used to mount the cache directories
 		for _, pathContainer := range baseImageConf.PathsToCache {
-			pathHostSide := makeCachePathHostSide(pathContainer)
+			pathHostSide, err := makeCachePathHostSide(pathContainer)
+			if err != nil {
+				return err
+			}
 			buildArgs = append(buildArgs, fmt.Sprintf("--mount=type=bind,source=%s,destination=%s", pathHostSide, pathContainer))
 		}
 	}

cmd/bob/devshim.go

@@ -221,18 +221,23 @@ func makeCacheDir(dir string) error {
 		return err
 	}
 
-	cacheCounterpart := makeCachePathHostSide(dir)
-
-	if err := os.MkdirAll(cacheCounterpart, 0755); err != nil {
+	cacheCounterpart, err := makeCachePathHostSide(dir)
+	if err != nil {
 		return err
 	}
 
 	return os.Symlink(cacheCounterpart, dir)
 }
 
 // "/go/pkg" => "/tmp/build/go/pkg" (at host-side)
-func makeCachePathHostSide(pathInContainer string) string {
-	return filepath.Join("/tmp/build/", pathInContainer)
+func makeCachePathHostSide(pathInContainer string) (string, error) {
+	dir := filepath.Join("/tmp/build/", pathInContainer)
+
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return "", err
+	}
+
+	return dir, nil
 }
 
 func readShimConfig() (*shimConfig, error) {