Add .gitattribute assisted language detection to blame, diff and render (#17590)

Use check attribute code to check the assigned language of a file and send that in to
chroma as a hint for the language of the file.

Signed-off-by: Andrew Thornton <art27@cantab.net>

2 files changed, 30 insertions, 8 deletions

diff --git a/modules/highlight/highlight.go b/modules/highlight/highlight.go
index 9a876d2a6b..04bd30bceb 100644
--- a/modules/highlight/highlight.go
+++ b/modules/highlight/highlight.go
@@ -55,7 +55,7 @@ func NewContext() {
 }
 
 // Code returns a HTML version of code string with chroma syntax highlighting classes
-func Code(fileName, code string) string {
+func Code(fileName, language, code string) string {
 	NewContext()
 
 	// diff view newline will be passed as empty, change to literal \n so it can be copied
@@ -69,9 +69,23 @@ func Code(fileName, code string) string {
 	}
 
 	var lexer chroma.Lexer
-	if val, ok := highlightMapping[filepath.Ext(fileName)]; ok {
-		//use mapped value to find lexer
-		lexer = lexers.Get(val)
+
+	if len(language) > 0 {
+		lexer = lexers.Get(language)
+
+		if lexer == nil {
+			// Attempt stripping off the '?'
+			if idx := strings.IndexByte(language, '?'); idx > 0 {
+				lexer = lexers.Get(language[:idx])
+			}
+		}
+	}
+
+	if lexer == nil {
+		if val, ok := highlightMapping[filepath.Ext(fileName)]; ok {
+			//use mapped value to find lexer
+			lexer = lexers.Get(val)
+		}
 	}
 
 	if lexer == nil {
@@ -119,7 +133,7 @@ func CodeFromLexer(lexer chroma.Lexer, code string) string {
 }
 
 // File returns a slice of chroma syntax highlighted lines of code
-func File(numLines int, fileName string, code []byte) []string {
+func File(numLines int, fileName, language string, code []byte) []string {
 	NewContext()
 
 	if len(code) > sizeLimit {
@@ -139,8 +153,16 @@ func File(numLines int, fileName string, code []byte) []string {
 	htmlw := bufio.NewWriter(&htmlbuf)
 
 	var lexer chroma.Lexer
-	if val, ok := highlightMapping[filepath.Ext(fileName)]; ok {
-		lexer = lexers.Get(val)
+
+	// provided language overrides everything
+	if len(language) > 0 {
+		lexer = lexers.Get(language)
+	}
+
+	if lexer == nil {
+		if val, ok := highlightMapping[filepath.Ext(fileName)]; ok {
+			lexer = lexers.Get(val)
+		}
 	}
 
 	if lexer == nil {
diff --git a/modules/highlight/highlight_test.go b/modules/highlight/highlight_test.go
index 29a15c0b53..3f47b6a48f 100644
--- a/modules/highlight/highlight_test.go
+++ b/modules/highlight/highlight_test.go
@@ -96,7 +96,7 @@ steps:
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			if got := File(tt.numLines, tt.fileName, []byte(tt.code)); !reflect.DeepEqual(got, tt.want) {
+			if got := File(tt.numLines, tt.fileName, "", []byte(tt.code)); !reflect.DeepEqual(got, tt.want) {
 				t.Errorf("File() = %v, want %v", got, tt.want)
 			}
 		})