[Autofill/Autocomplete Feature] Substring matching instead of prefix matching.

components/autofill/core/common/autofill_util.cc

+// 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.
+
+#include "components/autofill/core/common/autofill_util.h"
+
+#include <vector>
+
+#include "base/command_line.h"
+#include "base/i18n/case_conversion.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "components/autofill/core/common/autofill_switches.h"
+
+namespace autofill {
+
+bool IsFeatureSubstringMatchEnabled() {
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableSuggestionsWithSubstringMatch);
+}
+
+bool IsContentsPrefixOfSuggestionToken(const base::string16& field_suggestion,
+                                       const base::string16& field_contents,
+                                       bool case_sensitive) {
+  if (!IsFeatureSubstringMatchEnabled()) {
+    return false;
+  }
+
+  bool result = false;
+  std::vector<base::string16> suggestion_tokens;
+  Tokenize(field_suggestion, base::ASCIIToUTF16(" .,-_@"), &suggestion_tokens);
+
+  // Check whether the |field_contents| prefixes any of the |field_suggestion|'s
+  // token.
+  for (auto token : suggestion_tokens) {
+    result = StartsWith(token, field_contents, case_sensitive);

[Evan Stade, 2015/03/31 21:41:52]

this doesn't work if you type user@exa and the suggestion is user@example.com. I
think you should just search for the first occurrence of field_contents in
field_suggestion (without tokenization) then check if pos - 1 is a separator
character (or -1).

That would also not work if you typed "example" and the suggestion was
"texample@example.com", but the only time that's likely to come up is if you
typed "a" or something else really short/common, in which case it's arguable we
shouldn't be suggesting anything. But if you do want to handle that case you
need StartsAt to be able to return more results than just the first one.

[Pritam Nikam, 2015/04/01 09:10:37]

Done.

Modified ComputeRange() so that it will take care of these cases. Also added few
unit tests as well.

+    if (result)
+      break;
+  }
+
+  return result;
+}
+
+base::string16::size_type ComputeRange(const base::string16& field_suggestion,
+                                       const base::string16& field_contents,
+                                       size_t* start,
+                                       size_t* end) {
+  base::string16::size_type offset =
+      StartsAt(field_suggestion, field_contents, false);
+  if (base::string16::npos != offset) {
+    *start = offset + field_contents.size();
+    *end = field_suggestion.size();
+  }
+
+  return offset;
+}
+
+}  // namespace autofill