Fix LoadOutputCodeCache

2 files changed, 52 insertions, 4 deletions

diff --git a/deno_dir.go b/deno_dir.go
index 185f7abe0..d53bf85d8 100644
--- a/deno_dir.go
+++ b/deno_dir.go
@@ -61,15 +61,17 @@ func FetchRemoteSource(remoteUrl string, localFilename string) ([]byte, error) {
 	return ioutil.ReadAll(sourceReader)
 }
 
-func LoadOutputCodeCache(filename string, sourceCodeBuf []byte) (outputCode string, err error) {
+func LoadOutputCodeCache(filename string, sourceCodeBuf []byte) (
+	outputCode string, err error) {
 	cacheFn := CacheFileName(filename, sourceCodeBuf)
 	outputCodeBuf, err := ioutil.ReadFile(cacheFn)
 	if os.IsNotExist(err) {
-		err = nil // Ignore error if we can't load the cache.
-	} else if err != nil {
+		// Ignore error if we can't find the cache file.
+		err = nil
+	} else if err == nil {
 		outputCode = string(outputCodeBuf)
 	}
-	return
+	return outputCode, err
 }
 
 func UserHomeDir() string {
diff --git a/deno_dir_test.go b/deno_dir_test.go
new file mode 100644
index 000000000..fa3d68aed
--- /dev/null
+++ b/deno_dir_test.go
@@ -0,0 +1,46 @@
+package main
+
+import (
+	"io/ioutil"
+	"testing"
+)
+
+func SetCompileDirForTest(prefix string) {
+	dir, err := ioutil.TempDir("", prefix)
+	if err != nil {
+		panic(err)
+	}
+	CompileDir = dir
+}
+
+func TestLoadOutputCodeCache(t *testing.T) {
+	SetCompileDirForTest("TestLoadOutputCodeCache")
+
+	filename := "Hello.ts"
+	sourceCodeBuf := []byte("1+2")
+
+	cacheFn := CacheFileName(filename, sourceCodeBuf)
+
+	outputCode, err := LoadOutputCodeCache(filename, sourceCodeBuf)
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	if outputCode != "" {
+		t.Fatalf("Expected empty outputCode but got <<%s>>", outputCode)
+	}
+
+	// Now let's write to the cache file
+	err = ioutil.WriteFile(cacheFn, []byte("blah"), 0700)
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+
+	// Try it again.
+	outputCode, err = LoadOutputCodeCache(filename, sourceCodeBuf)
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	if outputCode != "blah" {
+		t.Fatalf("Bad outputCode but got <<%s>>", outputCode)
+	}
+}