feat: improve fail on change test

No longer relies on an arbitrary sleep.

Signed-off-by: Brian McGee <[email protected]>

cmd/root_test.go

@@ -9,7 +9,6 @@ import (
 	"path"
 	"path/filepath"
 	"regexp"
-	"slices"
 	"strings"
 	"testing"
 	"time"
@@ -575,28 +574,100 @@ func TestChangeWorkingDirectory(t *testing.T) {
 func TestFailOnChange(t *testing.T) {
 	as := require.New(t)
 
-	tempDir := test.TempExamples(t)
-	configPath := tempDir + "/touch.toml"
-
-	// test without any excludes
-	cfg := &config.Config{
-		FormatterConfigs: map[string]*config.Formatter{
-			"touch": {
-				Command:  "touch",
-				Includes: []string{"*"},
+	t.Run("change size", func(t *testing.T) {
+		tempDir := test.TempExamples(t)
+		configPath := filepath.Join(tempDir, "treefmt.toml")
+
+		cfg := &config.Config{
+			FormatterConfigs: map[string]*config.Formatter{
+				"append": {
+					// test-fmt-append is a helper defined in nix/packages/treefmt/formatters.nix which lets us append
+					// an arbitrary value to a list of files
+					Command:  "test-fmt-append",
+					Options:  []string{"hello"},
+					Includes: []string{"elm/*"},
+				},
 			},
-		},
-	}
+		}
+		test.WriteConfig(t, configPath, cfg)
 
-	test.WriteConfig(t, configPath, cfg)
-	_, _, err := treefmt(t, "--fail-on-change", "--config-file", configPath, "--tree-root", tempDir)
-	as.ErrorIs(err, formatCmd.ErrFailOnChange)
+		_, statz, err := treefmt(t, "--fail-on-change", "--config-file", configPath, "--tree-root", tempDir)
+		as.ErrorIs(err, formatCmd.ErrFailOnChange)
 
-	// test with no cache
-	t.Setenv("TREEFMT_FAIL_ON_CHANGE", "true")
-	test.WriteConfig(t, configPath, cfg)
-	_, _, err = treefmt(t, "--config-file", configPath, "--tree-root", tempDir, "--no-cache")
-	as.ErrorIs(err, formatCmd.ErrFailOnChange)
+		assertStats(t, as, statz, map[stats.Type]int{
+			stats.Traversed: 32,
+			stats.Matched:   2,
+			stats.Formatted: 2,
+			stats.Changed:   2,
+		})
+
+		// cached
+		_, statz, err = treefmt(t, "--fail-on-change", "--config-file", configPath, "--tree-root", tempDir)
+		as.NoError(err)
+
+		assertStats(t, as, statz, map[stats.Type]int{
+			stats.Traversed: 32,
+			stats.Matched:   2,
+			stats.Formatted: 0,
+			stats.Changed:   0,
+		})
+	})
+
+	t.Run("change modtime", func(t *testing.T) {
+		tempDir := test.TempExamples(t)
+		configPath := filepath.Join(tempDir, "treefmt.toml")
+
+		dateFormat := "2006 01 02 15:04.05"
+		replacer := strings.NewReplacer(" ", "", ":", "")
+
+		formatTime := func(t time.Time) string {
+			// go date formats are stupid
+			return replacer.Replace(t.Format(dateFormat))
+		}
+
+		writeConfig := func() {
+			// new mod time is in the next second
+			modTime := time.Now().Truncate(time.Second).Add(time.Second)
+
+			cfg := &config.Config{
+				FormatterConfigs: map[string]*config.Formatter{
+					"append": {
+						// test-fmt-modtime is a helper defined in nix/packages/treefmt/formatters.nix which lets us set
+						// a file's modtime to an arbitrary date.
+						// in this case, we move it forward more than a second so that our second level modtime comparison
+						// will detect it as a change.
+						Command:  "test-fmt-modtime",
+						Options:  []string{formatTime(modTime)},
+						Includes: []string{"haskell/*"},
+					},
+				},
+			}
+			test.WriteConfig(t, configPath, cfg)
+		}
+
+		writeConfig()
+
+		_, statz, err := treefmt(t, "--fail-on-change", "--config-file", configPath, "--tree-root", tempDir)
+		as.ErrorIs(err, formatCmd.ErrFailOnChange)
+
+		assertStats(t, as, statz, map[stats.Type]int{
+			stats.Traversed: 32,
+			stats.Matched:   7,
+			stats.Formatted: 7,
+			stats.Changed:   7,
+		})
+
+		// cached
+		_, statz, err = treefmt(t, "--fail-on-change", "--config-file", configPath, "--tree-root", tempDir)
+		as.NoError(err)
+
+		assertStats(t, as, statz, map[stats.Type]int{
+			stats.Traversed: 32,
+			stats.Matched:   7,
+			stats.Formatted: 0,
+			stats.Changed:   0,
+		})
+	})
 }
 
 func TestBustCacheOnFormatterChange(t *testing.T) {
@@ -1133,17 +1204,17 @@ func TestDeterministicOrderingInPipeline(t *testing.T) {
 			// a and b should execute in lexicographical order
 			// c should execute first since it has a priority of 1
 			"fmt-a": {
-				Command:  "test-fmt",
+				Command:  "test-fmt-append",
 				Options:  []string{"fmt-a"},
 				Includes: []string{"*.py"},
 			},
 			"fmt-b": {
-				Command:  "test-fmt",
+				Command:  "test-fmt-append",
 				Options:  []string{"fmt-b"},
 				Includes: []string{"*.py"},
 			},
 			"fmt-c": {
-				Command:  "test-fmt",
+				Command:  "test-fmt-append",
 				Options:  []string{"fmt-c"},
 				Includes: []string{"*.py"},
 				Priority: 1,
@@ -1306,21 +1377,6 @@ func treefmt(t *testing.T, args ...string) ([]byte, *stats.Stats, error) {
 	root.SetOut(tempOut)
 	root.SetErr(tempOut)
 
-	failOnChange := os.Getenv("TREEFMT_FAIL_ON_CHANGE") == "true" ||
-		slices.Index(args, "--fail-on-change") != -1
-
-	if failOnChange {
-		// record the start time
-		start := time.Now()
-
-		defer func() {
-			// Wait until we tick over into the next second before continuing.
-			// This ensures we correctly detect changes as treefmt compares modtime at second level precision.
-			waitUntil := start.Truncate(time.Second).Add(time.Second)
-			time.Sleep(time.Until(waitUntil))
-		}()
-	}
-
 	// execute the command
 	cmdErr := root.Execute()
 

nix/packages/treefmt/formatters.nix

@@ -18,9 +18,9 @@ with pkgs; [
   opentofu
   dos2unix
   yamlfmt
-  # util for unit testing
+  # utils for unit testing
   (pkgs.writeShellApplication {
-    name = "test-fmt";
+    name = "test-fmt-append";
     text = ''
       VALUE="$1"
       shift
@@ -31,4 +31,16 @@ with pkgs; [
       done
     '';
   })
+  (pkgs.writeShellApplication {
+    name = "test-fmt-modtime";
+    text = ''
+      VALUE="$1"
+      shift
+
+      # append value to each file
+      for FILE in "$@"; do
+          touch -t "$VALUE" "$FILE"
+      done
+    '';
+  })
 ]