Trigger calculation for inputs start with '='

In the current implementation, calculation rewriter is triggered only for
inputs end with "=", e.g. "1+1=".

With this CL, inputs start with "=" such as "=1+1" also trigger
calculation rewriter.

BUG=
TEST=unittest
REF_BUG=20315815
REF_CL=91563543

src/mozc_version_template.txt

@@ -1,6 +1,6 @@
 MAJOR=2
 MINOR=17
-BUILD=2243
+BUILD=2244
 REVISION=102
 # NACL_DICTIONARY_VERSION is the target version of the system dictionary to be
 # downloaded by NaCl Mozc.

src/rewriter/calculator/calculator.cc

@@ -49,6 +49,7 @@
 #include "base/logging.h"
 #include "base/number_util.h"
 #include "base/singleton.h"
+#include "base/string_piece.h"
 #include "base/util.h"
 
 // parser.c is a source file auto-generated by Lemon Parser.  It is not compiled
@@ -80,11 +81,11 @@ class CalculatorImpl : public CalculatorInterface {
   static const size_t kMaxLengthOfOperator = 3;
   static const size_t kBufferSizeOfOutputNumber = 32;
 
-  // Tokenizes |input| and sets the tokens into |tokens|.
-  // It returns false if |input| includes an invalid token or does not include
-  // both of a number token and an operator token. Parenthesis is not
-  // considered as an operator.
-  bool Tokenize(const string &input, TokenSequence *tokens) const;
+  // Tokenizes |expression_body| and sets the tokens into |tokens|.
+  // It returns false if |expression_body| includes an invalid token or
+  // does not include both of a number token and an operator token.
+  // Parenthesis is not considered as an operator.
+  bool Tokenize(StringPiece expression_body, TokenSequence *tokens) const;
 
   // Perform calculation with a given sequence of token.
   bool CalculateTokens(const TokenSequence &tokens,
@@ -122,14 +123,21 @@ bool CalculatorImpl::CalculateString(const string &key, string *result) const {
   string normalized_key;
   Util::FullWidthAsciiToHalfWidthAscii(key, &normalized_key);
 
-  // Expression is ended with '='.
-  if (normalized_key[normalized_key.size() - 1] != '=') {
+  StringPiece expression_body;
+  if (normalized_key.front() == '=') {
+    // Expression starts with '='.
+    expression_body.set(normalized_key.data() + 1, normalized_key.size() - 1);
+  } else if (normalized_key.back() == '=') {
+    // Expression is ended with '='.
+    expression_body.set(normalized_key.data(), normalized_key.size() - 1);
+  } else {
+    // Expression does not start nor end with '='.
     result->clear();
     return false;
   }
 
   TokenSequence tokens;
-  if (!Tokenize(normalized_key, &tokens)) {
+  if (!Tokenize(expression_body, &tokens)) {
     // normalized_key is not valid sequence of tokens
     result->clear();
     return false;
@@ -148,10 +156,10 @@ bool CalculatorImpl::CalculateString(const string &key, string *result) const {
   return true;
 }
 
-bool CalculatorImpl::Tokenize(const string &input,
+bool CalculatorImpl::Tokenize(StringPiece expression_body,
                               TokenSequence *tokens) const {
-  const char *current = input.data();
-  const char *end     = input.data() + input.size() - 1;  // omit '='
+  const char *current = expression_body.data();
+  const char *end     = expression_body.data() + expression_body.size();
   int num_operator = 0;  // Number of operators appeared
   int num_value    = 0;  // Number of values appeared
 

src/rewriter/calculator/calculator_test.cc

@@ -96,6 +96,8 @@ TEST(CalculatorTest, BasicTest) {
   VerifyRejection(calculator, "(5)=");
   // Expression must include at least one number.
   VerifyRejection(calculator, "()=");
+  // Expression with both heading and tailing '='s should be rejected.
+  VerifyRejection(calculator, "=(0-0)=");
 
   // Test for each operators
   VerifyCalculation(calculator, "38+2.5=", "40.5");
@@ -108,6 +110,8 @@ TEST(CalculatorTest, BasicTest) {
   VerifyCalculation(calculator, "2^10=", "1024");
   VerifyCalculation(calculator, "4*-2=", "-8");
   VerifyCalculation(calculator, "-10.3+3.5=", "-6.8");
+  // Expression can starts with '=' instead of ending with '='.
+  VerifyCalculation(calculator, "=-10.3+3.5", "-6.8");
 
   // Full width cases (some operators may appear as full width character).
   // "１２３４５＋６７８９０＝"

src/rewriter/calculator_rewriter.cc

@@ -174,8 +174,18 @@ bool CalculatorRewriter::InsertCandidate(const string &value,
       candidate->value = value;
       candidate->content_value = value;
     } else {       // with expression
-      candidate->value = expression + value;
-      candidate->content_value = expression + value;
+      DCHECK(!expression.empty());
+      if (expression.front() == '=') {
+        // Expression starts with '='.
+        // Appends value to the left of expression.
+        candidate->value = value + expression;
+        candidate->content_value = value + expression;
+      } else {
+        // Expression ends with '='.
+        // Appends value to the right of expression.
+        candidate->value = expression + value;
+        candidate->content_value = expression + value;
+      }
     }
   }
 

src/rewriter/calculator_rewriter_test.cc

@@ -220,6 +220,27 @@ TEST_F(CalculatorRewriterTest, SeparatedSegmentsTest) {
   EXPECT_EQ("1+1=2", segments.segment(0).candidate(index + 1).value);
 }
 
+// CalculatorRewriter should convert an expression starting with '='.
+TEST_F(CalculatorRewriterTest, ExpressionStartingWithEqualTest) {
+  // Pretend "=1+1" is calculated to "2".
+  calculator_mock().SetCalculatePair("=1+1", "2", true);
+
+  std::unique_ptr<CalculatorRewriter> calculator_rewriter(
+      BuildCalculatorRewriterWithConverterMock());
+  const ConversionRequest request;
+
+  Segments segments;
+  SetSegment("=1+1", "=1+1", &segments);
+  calculator_rewriter->Rewrite(request, &segments);
+  int index = GetIndexOfCalculatedCandidate(segments);
+  EXPECT_NE(-1, index);
+  EXPECT_EQ("2", segments.segment(0).candidate(index).value);
+  EXPECT_TRUE(ContainsCalculatedResult(
+      segments.segment(0).candidate(index + 1)));
+  // CalculatorRewriter should append the result to the side '=' exists.
+  EXPECT_EQ("2=1+1", segments.segment(0).candidate(index + 1).value);
+}
+
 // Verify the description of calculator candidate.
 TEST_F(CalculatorRewriterTest, DescriptionCheckTest) {
   // "５・（８／４）ー７％３＋６＾−１＊９＝"