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

components/password_manager/core/browser/password_autofill_manager.cc

Index: components/password_manager/core/browser/password_autofill_manager.cc
diff --git a/components/password_manager/core/browser/password_autofill_manager.cc b/components/password_manager/core/browser/password_autofill_manager.cc
index 15d5f7e3c8da005d4853f4dc3a8e78098bcaaebb..b727ab8d73b6b3698853ea6ede0da7234d63dd56 100644
--- a/components/password_manager/core/browser/password_autofill_manager.cc
+++ b/components/password_manager/core/browser/password_autofill_manager.cc
@@ -15,6 +15,7 @@
 #include "components/autofill/core/browser/suggestion.h"
 #include "components/autofill/core/common/autofill_constants.h"
 #include "components/autofill/core/common/autofill_data_validation.h"
+#include "components/autofill/core/common/autofill_util.h"
 #include "components/password_manager/core/browser/affiliation_utils.h"
 #include "components/password_manager/core/browser/password_manager_driver.h"
 #include "components/strings/grit/components_strings.h"
@@ -57,43 +58,67 @@ base::string16 GetHumanReadableRealm(const std::string& signon_realm) {
   return base::UTF8ToUTF16(signon_realm);
 }
 
+// Use this to check if a given suggestion matches the current contents of a
+// field.
+bool DoesSuggestionMatchContents(const base::string16& field_suggestion,
+                                 const base::string16& field_contents) {
+  return autofill::IsFeatureSubstringMatchEnabled() &&
+         autofill::IsContentsPrefixOfSuggestionToken(
+             field_suggestion, field_contents, autofill::CASE_IGNORE);
+}
+
+// Helper function to order prefix matched suggestions prior to substring
+// matched.
+bool OrderPrefixBeforeSubstring(const autofill::Suggestion& suggestion1,
+                                const autofill::Suggestion& suggestion2) {
+  return suggestion1.match < suggestion2.match;
+}
+
+// Helper function to fill username suggestion and adds it to |suggestions|.
+void FillUsernameSuggestion(const base::string16& field_suggestion,
+                            const base::string16& field_contents,
+                            const std::string& signon_realm,
+                            bool show_all,
+                            std::vector<autofill::Suggestion>* suggestions) {
+  bool substring_token_matched = false;
+  if (show_all || StartsWith(field_suggestion, field_contents, false) ||
+      (substring_token_matched =
+           DoesSuggestionMatchContents(field_suggestion, field_contents))) {
+    autofill::Suggestion suggestion(ReplaceEmptyUsername(field_suggestion));
+    suggestion.label = GetHumanReadableRealm(signon_realm);
+    suggestion.frontend_id = autofill::POPUP_ITEM_ID_PASSWORD_ENTRY;
+    suggestion.match = substring_token_matched
+                           ? autofill::Suggestion::SUBSTRING_MATCH
+                           : autofill::Suggestion::PREFIX_MATCH;
+    suggestions->push_back(suggestion);
+  }
+}
+
 // This function attempts to fill |suggestions| and |realms| form |fill_data|
 // based on |current_username|. Unless |show_all| is true, it only picks
-// suggestions where the username has |current_username| as a prefix.
+// suggestions where the username has |current_username| as a substring.
 void GetSuggestions(const autofill::PasswordFormFillData& fill_data,
                     const base::string16& current_username,
                     std::vector<autofill::Suggestion>* suggestions,
                     bool show_all) {
-  if (show_all ||
-      StartsWith(fill_data.username_field.value, current_username, false)) {
-    autofill::Suggestion suggestion(
-        ReplaceEmptyUsername(fill_data.username_field.value));
-    suggestion.label = GetHumanReadableRealm(fill_data.preferred_realm);
-    suggestion.frontend_id = autofill::POPUP_ITEM_ID_PASSWORD_ENTRY;
-    suggestions->push_back(suggestion);
-  }
+  FillUsernameSuggestion(fill_data.username_field.value, current_username,
+                         fill_data.preferred_realm, show_all, suggestions);
 
   for (const auto& login : fill_data.additional_logins) {
-    if (show_all || StartsWith(login.first, current_username, false)) {
-      autofill::Suggestion suggestion(ReplaceEmptyUsername(login.first));
-      suggestion.label = GetHumanReadableRealm(login.second.realm);
-      suggestion.frontend_id = autofill::POPUP_ITEM_ID_PASSWORD_ENTRY;
-      suggestions->push_back(suggestion);
-    }
+    FillUsernameSuggestion(login.first, current_username, login.second.realm,
+                           show_all, suggestions);
   }
 
   for (const auto& usernames : fill_data.other_possible_usernames) {
     for (size_t i = 0; i < usernames.second.size(); ++i) {
-      if (show_all ||
-          StartsWith(usernames.second[i], current_username, false)) {
-        autofill::Suggestion suggestion(
-            ReplaceEmptyUsername(usernames.second[i]));
-        suggestion.label = GetHumanReadableRealm(usernames.first.realm);
-        suggestion.frontend_id = autofill::POPUP_ITEM_ID_PASSWORD_ENTRY;
-        suggestions->push_back(suggestion);
-      }
+      FillUsernameSuggestion(usernames.second[i], current_username,
+                             usernames.first.realm, show_all, suggestions);
     }
   }
+
+  // Prefix matches should precede other token matches.
+  std::sort(suggestions->begin(), suggestions->end(),
+            OrderPrefixBeforeSubstring);
 }
 
 }  // namespace