[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 {
+
+namespace {
+
+base::string16 kTokenSeperatorsUTF16 = base::ASCIIToUTF16(" .,-_@");
+
+}  // namespace
+
+bool IsFeatureSubstringMatchEnabled() {
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableSuggestionsWithSubstringMatch);
+}
+
+bool IsContentsPrefixOfSuggestionToken(const base::string16& field_suggestion,

[vabr (Chromium), 2015/03/30 14:51:03]

What should IsContentsPrefixOfSuggestionToken("ab@cd.b", "b", false) return?
My guess is |true|, because "b" is the last token of "ab@cd.b". But the code
looks like it returns |false|, because the offset from line 41 will be 1, and
"a" is not a separator.
Am I missing something?

[Pritam Nikam, 2015/03/30 17:35:48]

You are right. I did a blunder here.

I want to keep it like below excerpt:

 42   if (base::string16::npos != offset) {
 43     std::vector<base::string16> suggestion_tokens, search_tokens;
 44     Tokenize(suggestion_string, kTokenSeperatorsUTF16, &suggestion_tokens);
 46 
 47     // Check whether the |search_string| prefixes any of the 
 49     // |suggestion_string|'s token.
 50     if (suggestion_tokens.size() != 0) {
 51       for (auto token : suggestion_tokens) {
 52         result = StartsWith(token, search_string, case_sensitive);
 53         if (result)
 54           break;
 55       }
 55     }

 that way may be I'm align with what I'm intended to. 

+                                       const base::string16& field_contents,
+                                       bool case_sensitive) {
+  if (field_suggestion.empty() || field_contents.empty()) {
+    return false;
+  }
+
+  bool result = false;
+  base::string16 search_string =
+      case_sensitive ? field_contents : base::i18n::ToLower(field_contents);
+  base::string16 suggestion_string =
+      case_sensitive ? field_suggestion : base::i18n::ToLower(field_suggestion);
+  base::string16::size_type offset = suggestion_string.find(search_string);
+  if (base::string16::npos != offset) {
+    // Check whether the |field_contents| begins with the |suggestion_string| or
+    // character right before |offset| is one of |kTokenSeperatorsUTF16|
+    // splitting characters.
+    if (0 == offset ||
+        base::ContainsOnlyChars(
+            base::internal::substr(suggestion_string, offset - 1, 1),
+            kTokenSeperatorsUTF16)) {
+      result = true;
+    }
+  }
+
+  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 user_input = base::i18n::ToLower(field_contents);
+  base::string16 suggestion = base::i18n::ToLower(field_suggestion);
+  base::string16::size_type offset = suggestion.find(user_input);
+  if (base::string16::npos != offset) {
+    *start = offset + user_input.size();
+    *end = suggestion.size();
+  }
+
+  return offset;
+}
+
+}  // namespace autofill