Simplified the logic of candidate filtering rule for Desktop.

1. When the top candidate is filtered, all other candidates were filtered. Disabled this filtering rule for the sake of simplicity.
2. Disabled the length and frequency based filtering.

PiperOrigin-RevId: 811682326

Author: taku910

src/prediction/user_history_predictor.cc

@@ -1459,8 +1459,8 @@ void UserHistoryPredictor::GetInputKeyFromRequest(
 }
 
 UserHistoryPredictor::ResultType UserHistoryPredictor::GetResultType(
-    const ConversionRequest& request, bool is_top_candidate,
-    uint32_t request_key_len, const Entry& entry) {
+    const ConversionRequest& request, uint32_t request_key_len,
+    const Entry& entry) {
   if (IsMixedConversionEnabled(request)) {
     // Don't show long history for mixed conversion
     if (entry.suggestion_freq() <= 1 && Util::CharsLen(entry.value()) >= 9) {
@@ -1470,35 +1470,7 @@ UserHistoryPredictor::ResultType UserHistoryPredictor::GetResultType(
     return ResultType::GOOD_RESULT;
   }
 
-  if (request.request_type() == ConversionRequest::SUGGESTION) {
-    // When bigram_boost is true, that means that previous user input
-    // and current input have bigram relation.
-    if (entry.bigram_boost()) {
-      return ResultType::GOOD_RESULT;
-    }
-
-    // Accepts short key prefix only when the frequency is >= 2.
-    const uint32_t min_prefix_len = entry.suggestion_freq() >= 2 ? 1 : 2;
-    if (request_key_len >= min_prefix_len) {
-      return ResultType::GOOD_RESULT;
-    }
-
-    // The top result of suggestion should be a VALID suggestion candidate.
-    // i.e., SuggestionTriggerFunc should return true for the first
-    // candidate.
-    // If user types "デスノート" too many times, "デスノート" will be
-    // suggested when user types "で". It is expected, but if user types
-    // "です" after that,  showing "デスノート" is annoying.
-    // In this situation, "です" is in the LRU, but SuggestionTriggerFunc
-    // returns false for "です", since it is short.
-    if (is_top_candidate) {
-      MOZC_VLOG(2) << "candidates size is 0";
-      return ResultType::STOP_ENUMERATION;
-    }
-
-    return ResultType::BAD_RESULT;
-  }
-
+  // No suppression rule on desktop for the sake of simplicity.
   return ResultType::GOOD_RESULT;
 }
 
@@ -1514,7 +1486,6 @@ std::vector<Result> UserHistoryPredictor::MakeResults(
   }
   const uint32_t request_key_len = Util::CharsLen(request.key());
 
-  size_t inserted_num = 0;
   size_t inserted_char_coverage = 0;
 
   std::vector<const UserHistoryPredictor::Entry*> entries;
@@ -1557,7 +1528,7 @@ std::vector<Result> UserHistoryPredictor::MakeResults(
     return true;
   };
 
-  while (inserted_num < max_prediction_size) {
+  while (entries.size() < max_prediction_size) {
     // |entry_queue| is a priority queue where the element
     // in the queue is sorted by the score defined in GetScore().
     const Entry* result_entry = entry_queue->Pop();
@@ -1566,11 +1537,8 @@ std::vector<Result> UserHistoryPredictor::MakeResults(
       break;
     }
 
-    const ResultType result =
-        GetResultType(request, entries.empty(), request_key_len, *result_entry);
-    if (result == ResultType::STOP_ENUMERATION) {
-      break;
-    } else if (result == ResultType::BAD_RESULT) {
+    if (GetResultType(request, request_key_len, *result_entry) ==
+        ResultType::BAD_RESULT) {
       continue;
     }
 
@@ -1583,14 +1551,12 @@ std::vector<Result> UserHistoryPredictor::MakeResults(
     // Break when the accumulated character length exceeds the
     // `max_prediction_char_coverage`. Allows to add at least one candidate.
     const size_t value_len = Util::CharsLen(result_entry->value());
-    if (max_prediction_char_coverage > 0 && inserted_num > 0 &&
+    if (max_prediction_char_coverage > 0 && !entries.empty() &&
         inserted_char_coverage + value_len > max_prediction_char_coverage) {
       break;
     }
 
     entries.emplace_back(result_entry);
-
-    ++inserted_num;
     inserted_char_coverage += value_len;
   }
 

src/prediction/user_history_predictor.h

@@ -204,7 +204,6 @@ class UserHistoryPredictor : public PredictorInterface {
   enum class ResultType {
     GOOD_RESULT,
     BAD_RESULT,
-    STOP_ENUMERATION,  // Do not insert and stop enumerations
   };
 
   // Returns true if this predictor should return results for the input.
@@ -243,7 +242,6 @@ class UserHistoryPredictor : public PredictorInterface {
   static bool HasBigramEntry(const Entry& entry, const Entry& prev_entry);
 
   static ResultType GetResultType(const ConversionRequest& request,
-                                  bool is_top_candidate,
                                   uint32_t request_key_len, const Entry& entry);
 
   // Returns true if entry is DEFAULT_ENTRY, satisfies certain conditions, and

src/prediction/user_history_predictor_test.cc

@@ -1334,6 +1334,14 @@ TEST_F(UserHistoryPredictorTest, UserHistoryPredictorClearTest) {
   predictor->ClearAllHistory();
   WaitForSyncer(predictor);
 
+  {
+    SegmentsProxy segments_proxy;
+    const ConversionRequest convreq1 =
+        SetUpInputForSuggestion("t", &composer_, &segments_proxy);
+    results = predictor->Predict(convreq1);
+    EXPECT_TRUE(results.empty());
+  }
+
   // input "testtest" 1 time
   for (int i = 0; i < 1; ++i) {
     SegmentsProxy segments_proxy;
@@ -1349,12 +1357,6 @@ TEST_F(UserHistoryPredictorTest, UserHistoryPredictorClearTest) {
     const ConversionRequest convreq1 =
         SetUpInputForSuggestion("t", &composer_, &segments_proxy);
     results = predictor->Predict(convreq1);
-    EXPECT_TRUE(results.empty());
-
-    segments_proxy.Clear();
-    const ConversionRequest convreq2 =
-        SetUpInputForSuggestion("testte", &composer_, &segments_proxy);
-    results = predictor->Predict(convreq2);
     EXPECT_FALSE(results.empty());
   }
 }
@@ -1752,7 +1754,7 @@ TEST_F(UserHistoryPredictorTest, MultiSegmentsMultiInput) {
   const ConversionRequest convreq2 =
       SetUpInputForSuggestion("た", &composer_, &segments_proxy);
   results = predictor->Predict(convreq2);
-  EXPECT_TRUE(results.empty());
+  EXPECT_FALSE(results.empty());  // "たろう"
 
   segments_proxy.Clear();
   const ConversionRequest convreq3 =
@@ -1867,7 +1869,7 @@ TEST_F(UserHistoryPredictorTest, MultiSegmentsSingleInput) {
   const ConversionRequest convreq3 =
       SetUpInputForSuggestion("た", &composer_, &segments_proxy);
   results = predictor->Predict(convreq3);
-  EXPECT_TRUE(results.empty());
+  EXPECT_FALSE(results.empty());  // たろうは
 
   segments_proxy.Clear();
   const ConversionRequest convreq4 =
@@ -2444,38 +2446,17 @@ TEST_F(UserHistoryPredictorTest, GetResultType) {
             .SetRequestType(ConversionRequest::SUGGESTION)
             .Build();
 
+    // Always return GOOD_RESULT
     entry.set_bigram_boost(true);
-    EXPECT_EQ(
-        UserHistoryPredictorTestPeer::GetResultType(convreq, false, 1, entry),
-        ResultType::GOOD_RESULT);
+    EXPECT_EQ(UserHistoryPredictorTestPeer::GetResultType(convreq, 1, entry),
+              ResultType::GOOD_RESULT);
 
     entry.set_bigram_boost(false);
-
-    // const uint32_t freq = entry.suggestion_freq();
-    // const uint32_t base_prefix_len = 3 - std::min<uint32_t>(2, freq);
-    // if (request_key_len >= base_prefix_len) {
-    // 3 >= 3 - min(2, 1) -> OK
-    entry.set_suggestion_freq(1);
-    EXPECT_EQ(
-        UserHistoryPredictorTestPeer::GetResultType(convreq, false, 3, entry),
-        ResultType::GOOD_RESULT);
-
-    // 1 >= 3 - min(2, 1) ->  NG
-    entry.set_suggestion_freq(1);
-    EXPECT_EQ(
-        UserHistoryPredictorTestPeer::GetResultType(convreq, false, 1, entry),
-        ResultType::BAD_RESULT);
-
-    // 1 >= 3 - min(2, 2) -> OK
     entry.set_suggestion_freq(1);
-    EXPECT_EQ(
-        UserHistoryPredictorTestPeer::GetResultType(convreq, false, 1, entry),
-        ResultType::BAD_RESULT);
-
-    entry.set_suggestion_freq(1);
-    EXPECT_EQ(
-        UserHistoryPredictorTestPeer::GetResultType(convreq, true, 1, entry),
-        ResultType::STOP_ENUMERATION);
+    EXPECT_EQ(UserHistoryPredictorTestPeer::GetResultType(convreq, 3, entry),
+              ResultType::GOOD_RESULT);
+    EXPECT_EQ(UserHistoryPredictorTestPeer::GetResultType(convreq, 1, entry),
+              ResultType::GOOD_RESULT);
   }
 
   // mobile
@@ -2488,21 +2469,18 @@ TEST_F(UserHistoryPredictorTest, GetResultType) {
     // entry.suggestion_freq() < 2 && Util::CharsLen(entry.value()) > 8
     entry.set_suggestion_freq(1);
     entry.set_value("よろしく");
-    EXPECT_EQ(
-        UserHistoryPredictorTestPeer::GetResultType(convreq, false, 1, entry),
-        ResultType::GOOD_RESULT);
+    EXPECT_EQ(UserHistoryPredictorTestPeer::GetResultType(convreq, 1, entry),
+              ResultType::GOOD_RESULT);
 
     entry.set_suggestion_freq(2);                 // high freq
     entry.set_value("よろしくおねがいします。");  // too long
-    EXPECT_EQ(
-        UserHistoryPredictorTestPeer::GetResultType(convreq, false, 1, entry),
-        ResultType::GOOD_RESULT);
+    EXPECT_EQ(UserHistoryPredictorTestPeer::GetResultType(convreq, 1, entry),
+              ResultType::GOOD_RESULT);
 
     entry.set_suggestion_freq(1);                 // low freq
     entry.set_value("よろしくおねがいします。");  // too long
-    EXPECT_EQ(
-        UserHistoryPredictorTestPeer::GetResultType(convreq, false, 1, entry),
-        ResultType::BAD_RESULT);
+    EXPECT_EQ(UserHistoryPredictorTestPeer::GetResultType(convreq, 1, entry),
+              ResultType::BAD_RESULT);
   }
 }