Mojom parser: Fix snippet algorithm.

mojom/mojom_parser/lexer/lexer_test.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package lexer
 
 import (
         "strings"
         "testing"
 )
@@ skipping 294 matching lines @@
 // TestTokenSnippetLongPrelude tests snippet generation in the presence of a
 // long line with many characters preceeding the token.
 func TestTokenSnippetLongPrelude(t *testing.T) {
         source := strings.Repeat(" ", 70) + "hello world"
         ts := Tokenize(source)
         expected := strings.Repeat(" ", 58) + "hello world\n"
         expected += strings.Repeat(" ", 58) + "^^^^^"
         checkEq(t, expected, ts.PeekNext().Snippet(source, false))
 }
 
+// TestTokenSnippetLongPreludeWithNewLine tests snippet generation in the presence of a
+// long line with many characters preceeding the token and then a newline after the token.
+func TestTokenSnippetLongPreludeWithNewLine(t *testing.T) {
+        source := strings.Repeat(" ", 70) + "hello world\n"
+        ts := Tokenize(source)
+        expected := strings.Repeat(" ", 58) + "hello world\n"
+        expected += strings.Repeat(" ", 58) + "^^^^^"
+        checkEq(t, expected, ts.PeekNext().Snippet(source, false))
+}
+
+// TestTokenSnippetLongPreludeWithSuffix tests snippet generation in the presence of a
+// long line with many characters preceeding the token and then some characters following on the same line.
+func TestTokenSnippetLongPreludeWithLongSuffix(t *testing.T) {
+        source := strings.Repeat(" ", 70) + "hello world " + strings.Repeat("x", 10)
+        ts := Tokenize(source)
+        expected := strings.Repeat(" ", 58) + "hello world xxxxxxxx\n"
+        expected += strings.Repeat(" ", 58) + "^^^^^"
+        checkEq(t, expected, ts.PeekNext().Snippet(source, false))
+}
+
 func TestFilteredTokens(t *testing.T) {
         source := "/* filtered1 */ hello world // filtered2"
         ts := Tokenize(source)
         ts.ConsumeNext()
         ts.ConsumeNext()
         filtered := ts.(*FilteredTokenStream).FilteredTokens()
         checkEq(t, MultiLineComment, filtered[0].Kind)
         checkEq(t, SingleLineComment, filtered[1].Kind)
 }
 
 func TestEmptyLine(t *testing.T) {
         ts := tokenizeUnfiltered("\n")
         checkEq(t, EmptyLine, ts.PeekNext().Kind)
         ts.ConsumeNext()
         checkEq(t, EOF, ts.PeekNext().Kind)
 }