add test case for -fail flag

cmd/templ/fmtcmd/main_test.go

@@ -84,6 +84,7 @@ func TestFormat(t *testing.T) {
 			Files: []string{
 				tp.testFiles["a.templ"].name,
 			},
+			FailIfChanged: false,
 		}); err != nil {
 			t.Fatalf("failed to run format command: %v", err)
 		}
@@ -101,6 +102,7 @@ func TestFormat(t *testing.T) {
 			Files: []string{
 				tp.testFiles["a.templ"].name,
 			},
+			FailIfChanged: false,
 		}); err != nil {
 			t.Fatalf("failed to run format command: %v", err)
 		}
@@ -112,4 +114,50 @@ func TestFormat(t *testing.T) {
 			t.Error(diff)
 		}
 	})
+
+	t.Run("fails when fail flag used and change occurs", func(t *testing.T) {
+		tp, err := setupProjectDir()
+		if err != nil {
+			t.Fatalf("failed to setup project dir: %v", err)
+		}
+		defer tp.cleanup()
+		if err = Run(log, nil, nil, Arguments{
+			Files: []string{
+				tp.testFiles["a.templ"].name,
+			},
+			FailIfChanged: true,
+		}); err == nil {
+			t.Fatal("command should have exited with an error and did not")
+		}
+		data, err := os.ReadFile(tp.testFiles["a.templ"].name)
+		if err != nil {
+			t.Fatalf("failed to read file: %v", err)
+		}
+		if diff := cmp.Diff(tp.testFiles["a.templ"].expected, string(data)); diff != "" {
+			t.Error(diff)
+		}
+	})
+
+	t.Run("passes when fail flag used and no change occurs", func(t *testing.T) {
+		tp, err := setupProjectDir()
+		if err != nil {
+			t.Fatalf("failed to setup project dir: %v", err)
+		}
+		defer tp.cleanup()
+		if err = Run(log, nil, nil, Arguments{
+			Files: []string{
+				tp.testFiles["c.templ"].name,
+			},
+			FailIfChanged: true,
+		}); err != nil {
+			t.Fatalf("failed to run format command: %v", err)
+		}
+		data, err := os.ReadFile(tp.testFiles["c.templ"].name)
+		if err != nil {
+			t.Fatalf("failed to read file: %v", err)
+		}
+		if diff := cmp.Diff(tp.testFiles["c.templ"].expected, string(data)); diff != "" {
+			t.Error(diff)
+		}
+	})
 }

cmd/templ/fmtcmd/testdata.txtar

@@ -22,7 +22,7 @@ templ b() {
 	<div><p>B
 </p></div>
 }
--- a.templ --
+-- b.templ --
 package test
 
 templ b() {
@@ -32,3 +32,23 @@ templ b() {
 		</p>
 	</div>
 }
+-- c.templ --
+package test
+
+templ c() {
+	<div>
+		<p>
+			C
+		</p>
+	</div>
+}
+-- c.templ --
+package test
+
+templ c() {
+	<div>
+		<p>
+			C
+		</p>
+	</div>
+}