refactor: make extension detection more robust

7z.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"io/fs"
 	"log"
+	"path/filepath"
 	"strings"
 
 	"github.com/bodgit/sevenzip"
@@ -37,7 +38,7 @@ func (z SevenZip) Match(_ context.Context, filename string, stream io.Reader) (M
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), z.Extension()) {
+	if filepath.Ext(strings.ToLower(filename)) == z.Extension() {
 		mr.ByName = true
 	}
 

brotli.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"io"
+	"path/filepath"
 	"strings"
 	"unicode/utf8"
 
@@ -26,7 +27,7 @@ func (br Brotli) Match(ctx context.Context, filename string, stream io.Reader) (
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), br.Extension()) {
+	if filepath.Ext(strings.ToLower(filename)) == br.Extension() {
 		mr.ByName = true
 	}
 

bz2.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"io"
+	"path/filepath"
 	"strings"
 
 	"github.com/dsnet/compress/bzip2"
@@ -25,7 +26,7 @@ func (bz Bz2) Match(_ context.Context, filename string, stream io.Reader) (Match
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), bz.Extension()) {
+	if filepath.Ext(strings.ToLower(filename)) == bz.Extension() {
 		mr.ByName = true
 	}
 

formats_test.go

@@ -114,6 +114,44 @@ func checkErr(t *testing.T, err error, msgFmt string, args ...any) {
 	t.Fatalf(msgFmt+": %s", args...)
 }
 
+func TestIdentifyFindFormatByFileName(t *testing.T) {
+	tests := []struct {
+		filename string
+		expected string
+	}{
+		{
+			filename: "test.tar",
+			expected: ".tar",
+		},
+		{
+			filename: "test.tar.bz2",
+			expected: ".tar.bz2",
+		},
+		{
+			filename: "test.tar.br",
+			expected: ".tar.br",
+		},
+		{
+			filename: "test.tar.bru",
+			expected: ".tar",
+		},
+		{
+			filename: "test.7z",
+			expected: ".7z",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.filename, func(t *testing.T) {
+			format, _, err := Identify(context.Background(), tt.filename, nil)
+			checkErr(t, err, "identifying")
+			if format.Extension() != tt.expected {
+				t.Errorf("unexpected extension: %v, expected: %v", format.Extension(), tt.expected)
+			}
+		})
+	}
+}
+
 func TestIdentifyDoesNotMatchContentFromTrimmedKnownHeaderHaving0Suffix(t *testing.T) {
 	// Using the outcome of `n, err := io.ReadFull(stream, buf)` without minding n
 	// may lead to a mis-characterization for cases with known header ending with 0x0

gz.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"io"
+	"path/filepath"
 	"strings"
 
 	"github.com/klauspost/compress/gzip"
@@ -37,7 +38,7 @@ func (gz Gz) Match(_ context.Context, filename string, stream io.Reader) (MatchR
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), gz.Extension()) {
+	if filepath.Ext(strings.ToLower(filename)) == gz.Extension() {
 		mr.ByName = true
 	}
 

lz4.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"io"
+	"path/filepath"
 	"strings"
 
 	"github.com/pierrec/lz4/v4"
@@ -25,7 +26,7 @@ func (lz Lz4) Match(_ context.Context, filename string, stream io.Reader) (Match
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), lz.Extension()) {
+	if filepath.Ext(strings.ToLower(filename)) == lz.Extension() {
 		mr.ByName = true
 	}
 

minlz.go

@@ -27,7 +27,7 @@ func (mz MinLZ) Match(_ context.Context, filename string, stream io.Reader) (Mat
 	var mr MatchResult
 
 	// match filename
-	if filepath.Ext(strings.ToLower(filename)) == ".mz" {
+	if filepath.Ext(strings.ToLower(filename)) == mz.Extension() {
 		mr.ByName = true
 	}
 

rar.go

@@ -10,6 +10,7 @@ import (
 	"log"
 	"os"
 	"path"
+	"path/filepath"
 	"strings"
 	"time"
 
@@ -60,7 +61,7 @@ func (r Rar) Match(_ context.Context, filename string, stream io.Reader) (MatchR
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), r.Extension()) {
+	if filepath.Ext(strings.ToLower(filename)) == r.Extension() {
 		mr.ByName = true
 	}
 

sz.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"io"
+	"path/filepath"
 	"strings"
 
 	"github.com/klauspost/compress/s2"
@@ -51,8 +52,8 @@ func (sz Sz) Match(_ context.Context, filename string, stream io.Reader) (MatchR
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), sz.Extension()) ||
-		strings.Contains(strings.ToLower(filename), ".s2") {
+	if filepath.Ext(strings.ToLower(filename)) == sz.Extension() ||
+		filepath.Ext(strings.ToLower(filename)) == ".s2" {
 		mr.ByName = true
 	}
 

xz.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"io"
+	"path/filepath"
 	"strings"
 
 	fastxz "github.com/mikelolasagasti/xz"
@@ -24,7 +25,7 @@ func (x Xz) Match(_ context.Context, filename string, stream io.Reader) (MatchRe
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), x.Extension()) {
+	if filepath.Ext(strings.ToLower(filename)) == x.Extension() {
 		mr.ByName = true
 	}
 

zip.go

@@ -10,6 +10,7 @@ import (
 	"log"
 	"os"
 	"path"
+	"path/filepath"
 	"strings"
 
 	szip "github.com/STARRY-S/zip"
@@ -85,7 +86,7 @@ func (z Zip) Match(_ context.Context, filename string, stream io.Reader) (MatchR
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), z.Extension()) {
+	if filepath.Ext(strings.ToLower(filename)) == z.Extension() {
 		mr.ByName = true
 	}
 

zlib.go

@@ -3,6 +3,7 @@ package archives
 import (
 	"context"
 	"io"
+	"path/filepath"
 	"strings"
 
 	"github.com/klauspost/compress/zlib"
@@ -24,7 +25,7 @@ func (zz Zlib) Match(_ context.Context, filename string, stream io.Reader) (Matc
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), zz.Extension()) {
+	if filepath.Ext(strings.ToLower(filename)) == zz.Extension() {
 		mr.ByName = true
 	}
 

zstd.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"io"
+	"path/filepath"
 	"strings"
 
 	"github.com/klauspost/compress/zstd"
@@ -26,7 +27,7 @@ func (zs Zstd) Match(_ context.Context, filename string, stream io.Reader) (Matc
 	var mr MatchResult
 
 	// match filename
-	if strings.Contains(strings.ToLower(filename), zs.Extension()) {
+	if filepath.Ext(strings.ToLower(filename)) == zs.Extension() {
 		mr.ByName = true
 	}