Just use a slice when rendering file (#16774)

Highlight currently uses a map which is memory inefficient. Switch to use a slice instead.

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

modules/highlight/highlight.go

@@ -116,8 +116,8 @@ func Code(fileName, code string) string {
 	return strings.TrimSuffix(htmlbuf.String(), "\n")
 }
 
-// File returns map with line lumbers and HTML version of code with chroma syntax highlighting classes
-func File(numLines int, fileName string, code []byte) map[int]string {
+// File returns a slice of chroma syntax highlighted lines of code
+func File(numLines int, fileName string, code []byte) []string {
 	NewContext()
 
 	if len(code) > sizeLimit {
@@ -171,9 +171,8 @@ func File(numLines int, fileName string, code []byte) map[int]string {
 		finalNewLine = code[len(code)-1] == '\n'
 	}
 
-	m := make(map[int]string, numLines)
-	for k, v := range strings.SplitN(htmlbuf.String(), "\n", numLines) {
-		line := k + 1
+	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 == "" {
@@ -183,26 +182,25 @@ func File(numLines int, fileName string, code []byte) map[int]string {
 		}
 		content = strings.TrimSuffix(content, `<span class="w">`)
 		content = strings.TrimPrefix(content, `</span>`)
-		m[line] = content
+		m = append(m, content)
 	}
 	if finalNewLine {
-		m[numLines+1] = "<span class=\"w\">\n</span>"
+		m = append(m, "<span class=\"w\">\n</span>")
 	}
 
 	return m
 }
 
 // return unhiglighted map
-func plainText(code string, numLines int) map[int]string {
-	m := make(map[int]string, numLines)
-	for k, v := range strings.SplitN(string(code), "\n", numLines) {
-		line := k + 1
+func plainText(code string, numLines int) []string {
+	m := make([]string, 0, numLines)
+	for _, v := range strings.SplitN(string(code), "\n", numLines) {
 		content := string(v)
 		//need to keep lines that are only \n so copy/paste works properly in browser
 		if content == "" {
 			content = "\n"
 		}
-		m[line] = gohtml.EscapeString(content)
+		m = append(m, gohtml.EscapeString(content))
 	}
 	return m
 }

modules/highlight/highlight_test.go

@@ -19,7 +19,7 @@ func TestFile(t *testing.T) {
 		numLines int
 		fileName string
 		code     string
-		want     map[int]string
+		want     []string
 	}{
 		{
 			name:     ".drone.yml",
@@ -38,22 +38,22 @@ steps:
 	- go build -v
 	- go test -v -race -coverprofile=coverage.txt -covermode=atomic
 `,
-			want: map[int]string{
-				1: `<span class="nt">kind</span><span class="p">:</span><span class="w"> </span><span class="l">pipeline</span>`,
-				2: `<span class="w"></span><span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">default</span>`,
-				3: `<span class="w">
+			want: []string{
+				`<span class="nt">kind</span><span class="p">:</span><span class="w"> </span><span class="l">pipeline</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>`,
-				4: `<span class="w"></span><span class="nt">steps</span><span class="p">:</span>`,
-				5: `<span class="w"></span>- <span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">test</span>`,
-				6: `<span class="w">	</span><span class="nt">image</span><span class="p">:</span><span class="w"> </span><span class="l">golang:1.13</span>`,
-				7: `<span class="w">	</span><span class="nt">environment</span><span class="p">:</span>`,
-				8: `<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>`,
-				9: `<span class="w">	</span><span class="nt">commands</span><span class="p">:</span>`,
-				10: `<span class="w"></span><span class="w">	</span>- <span class="l">go get -u</span>`,
-				11: `<span class="w">	</span>- <span class="l">go build -v</span>`,
-				12: `<span class="w">	</span>- <span class="l">go test -v -race -coverprofile=coverage.txt -covermode=atomic</span><span class="w">
+				`<span class="w"></span><span class="nt">steps</span><span class="p">:</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="nt">image</span><span class="p">:</span><span class="w"> </span><span class="l">golang:1.13</span>`,
+				`<span class="w">	</span><span class="nt">environment</span><span class="p">:</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="nt">commands</span><span class="p">:</span>`,
+				`<span class="w"></span><span class="w">	</span>- <span class="l">go get -u</span>`,
+				`<span class="w">	</span>- <span class="l">go build -v</span>`,
+				`<span class="w">	</span>- <span class="l">go test -v -race -coverprofile=coverage.txt -covermode=atomic</span><span class="w">
 </span>`,
-				13: `<span class="w">
+				`<span class="w">
 </span>`,
 			},
 		},
@@ -74,21 +74,21 @@ steps:
 	- go build -v
 	- go test -v -race -coverprofile=coverage.txt -covermode=atomic
 	`,
-			want: map[int]string{
-				1: `<span class="nt">kind</span><span class="p">:</span><span class="w"> </span><span class="l">pipeline</span>`,
-				2: `<span class="w"></span><span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">default  </span>`,
-				3: `<span class="w">
+			want: []string{
+				`<span class="nt">kind</span><span class="p">:</span><span class="w"> </span><span class="l">pipeline</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>`,
-				4: `<span class="w"></span><span class="nt">steps</span><span class="p">:</span>`,
-				5: `<span class="w"></span>- <span class="nt">name</span><span class="p">:</span><span class="w"> </span><span class="l">test</span>`,
-				6: `<span class="w">	</span><span class="nt">image</span><span class="p">:</span><span class="w"> </span><span class="l">golang:1.13</span>`,
-				7: `<span class="w">	</span><span class="nt">environment</span><span class="p">:</span>`,
-				8: `<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>`,
-				9: `<span class="w">	</span><span class="nt">commands</span><span class="p">:</span>`,
-				10: `<span class="w"></span><span class="w">	</span>- <span class="l">go get -u</span>`,
-				11: `<span class="w">	</span>- <span class="l">go build -v</span>`,
-				12: `<span class="w">	</span>- <span class="l">go test -v -race -coverprofile=coverage.txt -covermode=atomic</span>`,
-				13: `<span class="w">	</span>`,
+				`<span class="w"></span><span class="nt">steps</span><span class="p">:</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="nt">image</span><span class="p">:</span><span class="w"> </span><span class="l">golang:1.13</span>`,
+				`<span class="w">	</span><span class="nt">environment</span><span class="p">:</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="nt">commands</span><span class="p">:</span>`,
+				`<span class="w"></span><span class="w">	</span>- <span class="l">go get -u</span>`,
+				`<span class="w">	</span>- <span class="l">go build -v</span>`,
+				`<span class="w">	</span>- <span class="l">go test -v -race -coverprofile=coverage.txt -covermode=atomic</span>`,
+				`<span class="w">	</span>`,
 			},
 		},
 	}

templates/repo/view_file.tmpl

@@ -99,7 +99,8 @@
 				{{else}}
 				<table>
 					<tbody>
-						{{range $line, $code := .FileContent}}
+						{{range $idx, $code := .FileContent}}
+						{{$line := Add $idx 1}}
 						<tr>
 							<td id="L{{$line}}" class="lines-num">
 								<span id="L{{$line}}" data-line-number="{{$line}}"></span>