Adjust line detection in highlight.go (#20612)

The code for detection of lines in highlight.go is somewhat too complex
and doesn't take account of how Chroma is actually splitting things into
lines for us.

Remove both the .line and .cl classes from Chroma's HTML which made
the old conditional work again. This fixed Copy of YAML files while also 
reducing the amount of rendered HTML nodes.

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>

2 files changed, 68 insertions, 49 deletions

diff --git a/modules/highlight/highlight.go b/modules/highlight/highlight.go
index a72f26d5f0..d967df1f98 100644
--- a/modules/highlight/highlight.go
+++ b/modules/highlight/highlight.go
@@ -26,7 +26,7 @@ import (
 )
 
 // don't index files larger than this many bytes for performance purposes
-const sizeLimit = 1000000
+const sizeLimit = 1024 * 1024
 
 var (
 	// For custom user mapping
@@ -58,7 +58,7 @@ func NewContext() {
 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
+	// diff view newline will be passed as empty, change to literal '\n' so it can be copied
 	// preserve literal newline in blame view
 	if code == "" || code == "\n" {
 		return "\n"
@@ -104,6 +104,11 @@ func Code(fileName, language, code string) string {
 	return CodeFromLexer(lexer, code)
 }
 
+type nopPreWrapper struct{}
+
+func (nopPreWrapper) Start(code bool, styleAttr string) string { return "" }
+func (nopPreWrapper) End(code bool) string                     { return "" }
+
 // CodeFromLexer returns a HTML version of code string with chroma syntax highlighting classes
 func CodeFromLexer(lexer chroma.Lexer, code string) string {
 	formatter := html.New(html.WithClasses(true),
@@ -126,9 +131,9 @@ func CodeFromLexer(lexer chroma.Lexer, code string) string {
 		return code
 	}
 
-	htmlw.Flush()
+	_ = htmlw.Flush()
 	// Chroma will add newlines for certain lexers in order to highlight them properly
-	// Once highlighted, strip them here so they don't cause copy/paste trouble in HTML output
+	// Once highlighted, strip them here, so they don't cause copy/paste trouble in HTML output
 	return strings.TrimSuffix(htmlbuf.String(), "\n")
 }
 
@@ -141,7 +146,7 @@ func File(numLines int, fileName, language string, code []byte) []string {
 	}
 	formatter := html.New(html.WithClasses(true),
 		html.WithLineNumbers(false),
-		html.PreventSurroundingPre(true),
+		html.WithPreWrapper(nopPreWrapper{}),
 	)
 
 	if formatter == nil {
@@ -189,27 +194,19 @@ func File(numLines int, fileName, language string, code []byte) []string {
 		return plainText(string(code), numLines)
 	}
 
-	htmlw.Flush()
+	_ = htmlw.Flush()
 	finalNewLine := false
 	if len(code) > 0 {
 		finalNewLine = code[len(code)-1] == '\n'
 	}
 
-	m := make([]string, 0, numLines)
-	for _, v := range strings.SplitN(htmlbuf.String(), "\n", numLines) {
-		content := string(v)
-		// need to keep lines that are only \n so copy/paste works properly in browser
-		if content == "" {
-			content = "\n"
-		} else if content == `</span><span class="w">` {
-			content += "\n</span>"
-		} else if content == `</span></span><span class="line"><span class="cl">` {
-			content += "\n"
-		}
-		content = strings.TrimSuffix(content, `<span class="w">`)
-		content = strings.TrimPrefix(content, `</span>`)
-		m = append(m, content)
+	m := strings.SplitN(htmlbuf.String(), `</span></span><span class="line"><span class="cl">`, numLines)
+	if len(m) > 0 {
+		m[0] = m[0][len(`<span class="line"><span class="cl">`):]
+		last := m[len(m)-1]
+		m[len(m)-1] = last[:len(last)-len(`</span></span>`)]
 	}
+
 	if finalNewLine {
 		m = append(m, "<span class=\"w\">\n</span>")
 	}
@@ -219,14 +216,14 @@ func File(numLines int, fileName, language string, code []byte) []string {
 
 // return unhiglighted map
 func plainText(code string, numLines int) []string {
-	m := make([]string, 0, numLines)
-	for _, v := range strings.SplitN(string(code), "\n", numLines) {
-		content := string(v)
+	m := strings.SplitN(code, "\n", numLines)
+
+	for i, content := range m {
 		// need to keep lines that are only \n so copy/paste works properly in browser
 		if content == "" {
 			content = "\n"
 		}
-		m = append(m, gohtml.EscapeString(content))
+		m[i] = gohtml.EscapeString(content)
 	}
 	return m
 }
diff --git a/modules/highlight/highlight_test.go b/modules/highlight/highlight_test.go
index e5dfedd2b3..87628d1bbb 100644
--- a/modules/highlight/highlight_test.go
+++ b/modules/highlight/highlight_test.go
@@ -43,18 +43,29 @@ func TestFile(t *testing.T) {
 					- go test -v -race -coverprofile=coverage.txt -covermode=atomic
 			`),
 			want: util.Dedent(`
-				<span class="line"><span class="cl"><span class="nt">kind</span><span class="p">:</span><span class="w"> </span><span class="l">pipeline</span>
-				</span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">default</span>
-				</span></span><span class="line"><span class="cl">
-				</span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">steps</span><span class="p">:</span>
-				</span></span><span class="line"><span class="cl"><span class="w"></span>- <span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">test</span>
-				</span></span><span class="line"><span class="cl"><span class="w">	</span><span class="nt">image</span><span class="p">:</span><span class="w"> </span><span class="l">golang:1.13</span>
-				</span></span><span class="line"><span class="cl"><span class="w">	</span><span class="nt">environment</span><span class="p">:</span>
-				</span></span><span class="line"><span class="cl"><span class="w"></span><span class="w">		</span><span class="nt">GOPROXY</span><span class="p">:</span><span class="w"> </span><span class="l">https://goproxy.cn</span>
-				</span></span><span class="line"><span class="cl"><span class="w">	</span><span class="nt">commands</span><span class="p">:</span>
-				</span></span><span class="line"><span class="cl"><span class="w"></span><span class="w">	</span>- <span class="l">go get -u</span>
-				</span></span><span class="line"><span class="cl"><span class="w">	</span>- <span class="l">go build -v</span>
-				</span></span><span class="line"><span class="cl"><span class="w">	</span>- <span class="l">go test -v -race -coverprofile=coverage.txt -covermode=atomic</span></span></span>
+				<span class="nt">kind</span><span class="p">:</span><span class="w"> </span><span class="l">pipeline</span><span class="w">
+				</span>
+				<span class="w"></span><span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">default</span><span class="w">
+				</span>
+				<span class="w">
+				</span>
+				<span class="w"></span><span class="nt">steps</span><span class="p">:</span><span class="w">
+				</span>
+				<span class="w"></span>- <span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">test</span><span class="w">
+				</span>
+				<span class="w">	</span><span class="nt">image</span><span class="p">:</span><span class="w"> </span><span class="l">golang:1.13</span><span class="w">
+				</span>
+				<span class="w">	</span><span class="nt">environment</span><span class="p">:</span><span class="w">
+				</span>
+				<span class="w"></span><span class="w">		</span><span class="nt">GOPROXY</span><span class="p">:</span><span class="w"> </span><span class="l">https://goproxy.cn</span><span class="w">
+				</span>
+				<span class="w">	</span><span class="nt">commands</span><span class="p">:</span><span class="w">
+				</span>
+				<span class="w"></span><span class="w">	</span>- <span class="l">go get -u</span><span class="w">
+				</span>
+				<span class="w">	</span>- <span class="l">go build -v</span><span class="w">
+				</span>
+				<span class="w">	</span>- <span class="l">go test -v -race -coverprofile=coverage.txt -covermode=atomic</span>
 			`),
 		},
 		{
@@ -76,19 +87,30 @@ func TestFile(t *testing.T) {
 					- go test -v -race -coverprofile=coverage.txt -covermode=atomic
 			`)+"\n", "name: default", "name: default  ", 1),
 			want: util.Dedent(`
-				<span class="line"><span class="cl"><span class="nt">kind</span><span class="p">:</span><span class="w"> </span><span class="l">pipeline</span>
-				</span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">default  </span>
-				</span></span><span class="line"><span class="cl">
-				</span></span><span class="line"><span class="cl"><span class="w"></span><span class="nt">steps</span><span class="p">:</span>
-				</span></span><span class="line"><span class="cl"><span class="w"></span>- <span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">test</span>
-				</span></span><span class="line"><span class="cl"><span class="w">	</span><span class="nt">image</span><span class="p">:</span><span class="w"> </span><span class="l">golang:1.13</span>
-				</span></span><span class="line"><span class="cl"><span class="w">	</span><span class="nt">environment</span><span class="p">:</span>
-				</span></span><span class="line"><span class="cl"><span class="w"></span><span class="w">		</span><span class="nt">GOPROXY</span><span class="p">:</span><span class="w"> </span><span class="l">https://goproxy.cn</span>
-				</span></span><span class="line"><span class="cl"><span class="w">	</span><span class="nt">commands</span><span class="p">:</span>
-				</span></span><span class="line"><span class="cl"><span class="w"></span><span class="w">	</span>- <span class="l">go get -u</span>
-				</span></span><span class="line"><span class="cl"><span class="w">	</span>- <span class="l">go build -v</span>
-				</span></span><span class="line"><span class="cl"><span class="w">	</span>- <span class="l">go test -v -race -coverprofile=coverage.txt -covermode=atomic</span>
-				</span></span>
+				<span class="nt">kind</span><span class="p">:</span><span class="w"> </span><span class="l">pipeline</span><span class="w">
+				</span>
+				<span class="w"></span><span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">default  </span><span class="w">
+				</span>
+				<span class="w">
+				</span>
+				<span class="w"></span><span class="nt">steps</span><span class="p">:</span><span class="w">
+				</span>
+				<span class="w"></span>- <span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">test</span><span class="w">
+				</span>
+				<span class="w">	</span><span class="nt">image</span><span class="p">:</span><span class="w"> </span><span class="l">golang:1.13</span><span class="w">
+				</span>
+				<span class="w">	</span><span class="nt">environment</span><span class="p">:</span><span class="w">
+				</span>
+				<span class="w"></span><span class="w">		</span><span class="nt">GOPROXY</span><span class="p">:</span><span class="w"> </span><span class="l">https://goproxy.cn</span><span class="w">
+				</span>
+				<span class="w">	</span><span class="nt">commands</span><span class="p">:</span><span class="w">
+				</span>
+				<span class="w"></span><span class="w">	</span>- <span class="l">go get -u</span><span class="w">
+				</span>
+				<span class="w">	</span>- <span class="l">go build -v</span><span class="w">
+				</span>
+				<span class="w">	</span>- <span class="l">go test -v -race -coverprofile=coverage.txt -covermode=atomic</span><span class="w">
+				</span>
 				<span class="w">
 				</span>
 			`),