Add newlines in line number spans when wrapping in an HTML table.

Since these are wrapped in a `<pre>`, newlines hint the browser that the
line numbers should be on separate lines. This helps when rendering
content with broken CSS, or in a text-only browser.

formatters/html/html.go

@@ -169,7 +169,7 @@ func (f *Formatter) writeHTML(w io.Writer, style *chroma.Style, tokens []*chroma
 				fmt.Fprintf(w, "<span%s>", f.styleAttr(css, chroma.LineHighlight))
 			}
 
-			fmt.Fprintf(w, "<span%s>%*d</span>", f.styleAttr(css, chroma.LineNumbersTable), lineDigits, line)
+			fmt.Fprintf(w, "<span%s>%*d\n</span>", f.styleAttr(css, chroma.LineNumbersTable), lineDigits, line)
 
 			if highlight {
 				fmt.Fprintf(w, "</span>")
@@ -327,7 +327,7 @@ func (f *Formatter) styleToCSS(style *chroma.Style) map[chroma.TokenType]string
 	lineNumbersStyle := "margin-right: 0.4em; padding: 0 0.4em 0 0.4em;"
 	// All rules begin with default rules followed by user provided rules
 	classes[chroma.LineNumbers] = lineNumbersStyle + classes[chroma.LineNumbers]
-	classes[chroma.LineNumbersTable] = lineNumbersStyle + " display: block;" + classes[chroma.LineNumbersTable]
+	classes[chroma.LineNumbersTable] = lineNumbersStyle + classes[chroma.LineNumbersTable]
 	classes[chroma.LineHighlight] = "display: block; width: 100%;" + classes[chroma.LineHighlight]
 	classes[chroma.LineTable] = "border-spacing: 0; padding: 0; margin: 0; border: 0; width: auto; overflow: auto; display: block;" + classes[chroma.LineTable]
 	classes[chroma.LineTableTD] = "vertical-align: top; padding: 0; margin: 0; border: 0;" + classes[chroma.LineTableTD]

formatters/html/html_test.go

@@ -92,3 +92,22 @@ func TestClassPrefix(t *testing.T) {
 		t.Error("Stylesheets should have a class prefix")
 	}
 }
+
+func TestTableLineNumberNewlines(t *testing.T) {
+	f := New(WithClasses(), WithLineNumbers(), LineNumbersInTable())
+	it, err := lexers.Get("go").Tokenise(nil, "package main\nfunc main()\n{\nprintln(`hello world`)\n}\n")
+	assert.NoError(t, err)
+
+	var buf bytes.Buffer
+	err = f.Format(&buf, styles.Fallback, it)
+	assert.NoError(t, err)
+
+	// Don't bother testing the whole output, just verify it's got line numbers
+	// in a <pre>-friendly format.
+	// Note: placing the newlines inside the <span> lets browser selections look
+	// better, instead of "skipping" over the span margin.
+	assert.Contains(t, buf.String(), `<span class="lnt">2
+</span><span class="lnt">3
+</span><span class="lnt">4
+</span>`)
+}