Truncate file when opening file in json output

pkg/cmd/scan/output/json.go

@@ -21,7 +21,7 @@ func NewJSON(path string) *JSON {
 func (c *JSON) Write(analysis *analyser.Analysis) error {
 	file := os.Stdout
 	if !isStdOut(c.path) {
-		f, err := os.OpenFile(c.path, os.O_CREATE|os.O_RDWR, 0600)
+		f, err := os.OpenFile(c.path, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0600)
 		if err != nil {
 			return err
 		}

pkg/cmd/scan/output/json_test.go

@@ -157,3 +157,39 @@ func TestJSON_Write_stdout(t *testing.T) {
 		})
 	}
 }
+
+func TestJSON_WriteMultiplesTimesInSameFile(t *testing.T) {
+	emptyAnalysis := &analyser.Analysis{}
+	longerAnalysis := fakeAnalysis()
+	tempDir := t.TempDir()
+	tempFile, err := ioutil.TempFile(tempDir, "result")
+	if err != nil {
+		t.Fatal(err)
+	}
+	c := NewJSON(tempFile.Name())
+
+	if err := c.Write(longerAnalysis); err != nil {
+		t.Errorf("First write error = %v", err)
+	}
+
+	if err := c.Write(emptyAnalysis); err != nil {
+		t.Errorf("Second write error = %v", err)
+	}
+
+	result, err := ioutil.ReadFile(tempFile.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	goldenFileName := "output_multiples_times.json"
+	expectedFilePath := path.Join("./testdata/", goldenFileName)
+	if *goldenfile.Update == goldenFileName {
+		if err := ioutil.WriteFile(expectedFilePath, result, 0600); err != nil {
+			t.Fatal(err)
+		}
+	}
+	expected, err := ioutil.ReadFile(expectedFilePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, string(expected), string(result))
+}

pkg/cmd/scan/output/testdata/output_multiples_times.json

@@ -0,0 +1,15 @@
+{
+	"summary": {
+		"total_resources": 0,
+		"total_drifted": 0,
+		"total_unmanaged": 0,
+		"total_missing": 0,
+		"total_managed": 0
+	},
+	"managed": null,
+	"unmanaged": null,
+	"missing": null,
+	"differences": null,
+	"coverage": 0,
+	"alerts": null
+}