feat: add path of failed snapshot on diff report (#69)

* chore: misc changes on unit tests

* feat: add path of failed snapshot on diff report

internal/test/test.go

@@ -47,7 +47,7 @@ func (m MockTestingT) Log(args ...interface{}) {
 }
 
 // Equal asserts expected and received have deep equality
-func Equal(t *testing.T, expected, received interface{}) {
+func Equal[A any](t *testing.T, expected, received A) {
 	t.Helper()
 	if !reflect.DeepEqual(expected, received) {
 		t.Errorf("\n[expected]: %v\n[received]: %v", expected, received)
@@ -77,6 +77,20 @@ func CreateTempFile(t *testing.T, data string) string {
 	return path
 }
 
+// GetFileContent returns the contents of a file
+//
+// it errors if file doesn't exist
+func GetFileContent(t *testing.T, name string) string {
+	t.Helper()
+
+	content, err := os.ReadFile(name)
+	if err != nil {
+		t.Error(err)
+	}
+
+	return string(content)
+}
+
 func True(t *testing.T, val bool) {
 	t.Helper()
 
@@ -94,9 +108,17 @@ func False(t *testing.T, val bool) {
 }
 
 func Nil(t *testing.T, val interface{}) {
+	t.Helper()
 	v := reflect.ValueOf(val)
 
 	if val != nil && !v.IsNil() {
 		t.Errorf("expected nil but got %v", val)
 	}
 }
+
+func NoError(t *testing.T, err error) {
+	t.Helper()
+	if err != nil {
+		t.Errorf("expected no error but got %s", err)
+	}
+}

snaps/__snapshots__/diff_test.snap

@@ -1,26 +1,32 @@
 
-[TestDiff/should_print_header_consistently - 1]
+[TestDiff/should_build_diff_report_consistently - 1]
 
 - Snapshot    - 20
 + Received + 10000
 
-
+mock-diff
+at snap/path:10
+
 ---
 
-[TestDiff/should_print_header_consistently - 2]
+[TestDiff/should_build_diff_report_consistently - 2]
 
 - Snapshot - 10000
 + Received    + 20
 
-
+mock-diff
+at snap/path:20
+
 ---
 
 [TestDiff/with_color/should_apply_highlights_on_single_line_diff - 1]
 
 - Snapshot - 20
 + Received + 20
 
-- abcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd+ abcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcf
+- abcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd+ abcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcf
+at snap/path:10
+
 ---
 
 [TestDiff/with_color/multiline_diff - 1]
@@ -48,7 +54,9 @@
 +                                   Sed lorem felis, condimentum eget vehicula non, sagittis sit amet diam. 
 +                                   Vivamus ut sapien at erat imperdiet suscipit id a lectus.
 +                                   Another Line added.
-
+
+at snap/path:10
+
 ---
 
 [TestDiff/no_color/should_apply_highlights_on_single_line_diff - 1]
@@ -59,6 +67,8 @@
 - abcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd
 + abcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcfabcf
 
+at snap/path:10
+
 ---
 
 [TestDiff/no_color/multiline_diff - 1]
@@ -87,4 +97,14 @@
 +       Vivamus ut sapien at erat imperdiet suscipit id a lectus.
 +       Another Line added.
 
+at snap/path:20
+
+---
+
+[TestDiff/should_not_print_snapshot_line_if_not_provided - 1]
+
+- Snapshot  - 2
++ Received + 10
+
+there is a diff here
 ---

snaps/clean_test.go

@@ -114,17 +114,6 @@ func setupTempExamineFiles(t *testing.T) (map[string]map[string]int, string, str
 	return tests, dir1, dir2
 }
 
-func getFileContent(t *testing.T, name string) string {
-	t.Helper()
-
-	content, err := os.ReadFile(name)
-	if err != nil {
-		t.Error(err)
-	}
-
-	return string(content)
-}
-
 func TestExamineFiles(t *testing.T) {
 	t.Run("should parse files", func(t *testing.T) {
 		tests, dir1, dir2 := setupTempExamineFiles(t)
@@ -182,7 +171,7 @@ func TestExamineSnaps(t *testing.T) {
 		obsolete, err := examineSnaps(tests, used, "", shouldUpdate)
 
 		test.Equal(t, []string{}, obsolete)
-		test.Nil(t, err)
+		test.NoError(t, err)
 	})
 
 	t.Run("should report two obsolete snapshots and not change content", func(t *testing.T) {
@@ -199,11 +188,11 @@ func TestExamineSnaps(t *testing.T) {
 		delete(tests[used[1]], "TestDir2_2/TestSimple")
 
 		obsolete, err := examineSnaps(tests, used, "", shouldUpdate)
-		content1 := getFileContent(t, used[0])
-		content2 := getFileContent(t, used[1])
+		content1 := test.GetFileContent(t, used[0])
+		content2 := test.GetFileContent(t, used[1])
 
 		test.Equal(t, []string{"TestDir1_3/TestSimple - 2", "TestDir2_2/TestSimple - 1"}, obsolete)
-		test.Nil(t, err)
+		test.NoError(t, err)
 
 		// Content of snaps is not changed
 		test.Equal(t, mockSnap1, content1)
@@ -222,8 +211,8 @@ func TestExamineSnaps(t *testing.T) {
 		delete(tests[used[1]], "TestDir2_1/TestSimple")
 
 		obsolete, err := examineSnaps(tests, used, "", shouldUpdate)
-		content1 := getFileContent(t, used[0])
-		content2 := getFileContent(t, used[1])
+		content1 := test.GetFileContent(t, used[0])
+		content2 := test.GetFileContent(t, used[1])
 
 		expected1 := `
 [TestDir1_1/TestSimple - 1]
@@ -255,7 +244,7 @@ string hello world 2 2 1
 		},
 			obsolete,
 		)
-		test.Nil(t, err)
+		test.NoError(t, err)
 
 		// Content of snaps is not changed
 		test.Equal(t, expected1, content1)

snaps/diff.go

@@ -1,6 +1,7 @@
 package snaps
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"strconv"
@@ -72,7 +73,8 @@ func getUnifiedDiff(a, b string) (string, int, int) {
 				received := strings.Join(aLines[i1:i2], "")
 
 				if shouldPrintHighlights(expected, received) {
-					i, d := singlelineDiff(&s, received, expected)
+					diff, i, d := singlelineDiff(received, expected)
+					s.WriteString(diff)
 					inserted += i
 					deleted += d
 
@@ -113,23 +115,6 @@ func getUnifiedDiff(a, b string) (string, int, int) {
 	return s.String(), inserted, deleted
 }
 
-// header of a diff report
-//
-// e.g.
-//   - Snapshot - 10
-//   - Received -  2
-func header(inserted, deleted int) string {
-	var s strings.Builder
-	iPadding, dPadding := intPadding(inserted, deleted)
-
-	s.WriteString("\n")
-	colors.FprintDelete(&s, fmt.Sprintf("Snapshot %s- %d\n", dPadding, deleted))
-	colors.FprintInsert(&s, fmt.Sprintf("Received %s+ %d\n", iPadding, inserted))
-	s.WriteString("\n")
-
-	return s.String()
-}
-
 func printRange(w io.Writer, opcodes []difflib.OpCode) {
 	first, last := opcodes[0], opcodes[len(opcodes)-1]
 	range1 := difflib.FormatRangeUnified(first.I1, last.I2)
@@ -161,57 +146,87 @@ func intPadding(inserted, deleted int) (string, string) {
 	return strings.Repeat(" ", -diff), ""
 }
 
-func singlelineDiff(s *strings.Builder, expected, received string) (int, int) {
+func singlelineDiff(expected, received string) (string, int, int) {
 	diffs := dmp.DiffCleanupSemantic(
 		dmp.DiffMain(expected, received, false),
 	)
 	if len(diffs) == 1 && diffs[0].Type == diffEqual {
-		// -1 means no diffs
-		return -1, 0
+		return "", -1, -1
 	}
 
 	var inserted, deleted int
-	var i strings.Builder
+	a := &bytes.Buffer{}
+	b := &bytes.Buffer{}
 
-	colors.FprintBg(s, colors.RedBg, colors.Reddiff, "- ")
-	colors.FprintBg(&i, colors.GreenBG, colors.Greendiff, "+ ")
+	colors.FprintBg(a, colors.RedBg, colors.Reddiff, "- ")
+	colors.FprintBg(b, colors.GreenBG, colors.Greendiff, "+ ")
 
 	for _, diff := range diffs {
 		switch diff.Type {
 		case diffDelete:
 			deleted++
-			colors.FprintDeleteBold(s, diff.Text)
+			colors.FprintDeleteBold(a, diff.Text)
 		case diffInsert:
 			inserted++
-			colors.FprintInsertBold(&i, diff.Text)
+			colors.FprintInsertBold(b, diff.Text)
 		case diffEqual:
-			colors.FprintBg(s, colors.RedBg, colors.Reddiff, diff.Text)
-			colors.FprintBg(&i, colors.GreenBG, colors.Greendiff, diff.Text)
+			colors.FprintBg(a, colors.RedBg, colors.Reddiff, diff.Text)
+			colors.FprintBg(b, colors.GreenBG, colors.Greendiff, diff.Text)
 		}
 	}
 
-	s.WriteString(i.String())
+	a.Write(b.Bytes())
 
-	return inserted, deleted
+	return a.String(), inserted, deleted
 }
 
-func prettyDiff(expected, received string) string {
-	if expected == received {
+/*
+buildDiffReport creates a report with diffs it contains a header the diff body and a footer
+
+header of a diff report
+
+	e.g.
+	  - Snapshot - 10
+	  - Received + 2
+
+body contains the diffs
+
+footer contains the relative path of snapshot
+
+	e.g. at ../__snapshots__/example_test.snap:25
+*/
+func buildDiffReport(inserted, deleted int, diff, name string, line int) string {
+	if diff == "" {
 		return ""
 	}
+	var s strings.Builder
+	s.Grow(len(diff))
 
-	if shouldPrintHighlights(expected, received) {
-		var diff strings.Builder
-		if i, d := singlelineDiff(&diff, expected, received); i != -1 {
-			return header(i, d) + diff.String()
-		}
+	iPadding, dPadding := intPadding(inserted, deleted)
 
-		return ""
+	s.WriteString("\n")
+	colors.FprintDelete(&s, fmt.Sprintf("Snapshot %s- %d\n", dPadding, deleted))
+	colors.FprintInsert(&s, fmt.Sprintf("Received %s+ %d\n", iPadding, inserted))
+	s.WriteString("\n")
+
+	s.WriteString(diff)
+
+	if name != "" {
+		colors.Fprint(&s, colors.Dim, fmt.Sprintf("\nat %s:%d\n", name, line))
 	}
 
-	if diff, i, d := getUnifiedDiff(expected, received); diff != "" {
-		return header(i, d) + diff
+	return s.String()
+}
+
+func prettyDiff(expected, received, name string, line int) string {
+	if expected == received {
+		return ""
+	}
+	differ := getUnifiedDiff
+	if shouldPrintHighlights(expected, received) {
+		differ = singlelineDiff
 	}
 
-	return ""
+	diff, i, d := differ(expected, received)
+	return buildDiffReport(i, d, diff, name, line)
 }