Implement minus flag.

format.cc

@@ -137,7 +137,7 @@ void FormatDecimal(char *buffer, uint64_t value, unsigned num_digits) {
 // Throws Exception(message) if format contains '}', otherwise throws
 // FormatError reporting unmatched '{'. The idea is that unmatched '{'
 // should override other errors.
-void Formatter::ReportError(const char *s, const std::string &message) const {
+void Formatter::ReportError(const char *s, StringRef message) const {
   for (int num_open_braces = num_open_braces_; *s; ++s) {
     if (*s == '{') {
       ++num_open_braces;
@@ -459,15 +459,21 @@ void Formatter::DoFormat() {
       }
 
       // Parse sign.
-      if (*s == '+') {
-        ++s;
-        if (arg.type > LAST_NUMERIC_TYPE)
-          ReportError(s, "format specifier '+' requires numeric argument");
+      switch (*s) {
+      case '+':
+        spec.flags |= PLUS_FLAG;
+        // Fall through.
+      case '-':
+        if (arg.type > LAST_NUMERIC_TYPE) {
+          ReportError(s,
+              Format("format specifier '{0}' requires numeric argument") << *s);
+        }
         if (arg.type == UINT || arg.type == ULONG) {
           ReportError(s,
-              "format specifier '+' requires signed argument");
+              Format("format specifier '{0}' requires signed argument") << *s);
         }
-        spec.flags |= PLUS_FLAG;
+        ++s;
+        break;
       }
 
       // Parse width and zero flag.

format.h

@@ -117,6 +117,33 @@ void Array<T, SIZE>::append(const T *begin, const T *end) {
 class ArgInserter;
 }
 
+// A reference to a string. It can be constructed from a C string,
+// std::string or as a result of a formatting operation. It is most useful
+// as a parameter type to allow passing different types of strings in a
+// function, for example:
+//   void SetName(StringRef s) {
+//     std::string name = s;
+//     ...
+//   }
+class StringRef {
+ private:
+  const char *data_;
+  mutable std::size_t size_;
+
+ public:
+  StringRef(const char *s, std::size_t size = 0) : data_(s), size_(size) {}
+  StringRef(const std::string &s) : data_(s.c_str()), size_(s.size()) {}
+
+  operator std::string() const { return std::string(data_, size()); }
+
+  const char *c_str() const { return data_; }
+
+  std::size_t size() const {
+    if (size_ == 0) size_ = std::strlen(data_);
+    return size_;
+  }
+};
+
 class FormatError : public std::runtime_error {
  public:
   explicit FormatError(const std::string &message)
@@ -269,7 +296,7 @@ class Formatter {
     args_.push_back(&arg);
   }
 
-  void ReportError(const char *s, const std::string &message) const;
+  void ReportError(const char *s, StringRef message) const;
 
   char *PrepareFilledBuffer(unsigned size, const FormatSpec &spec, char sign);
 
@@ -325,33 +352,6 @@ class Formatter {
   std::string str() const { return std::string(&buffer_[0], buffer_.size()); }
 };
 
-// A reference to a string. It can be constructed from a C string,
-// std::string or as a result of a formatting operation. It is most useful
-// as a parameter type to allow passing different types of strings in a
-// function, for example:
-//   void SetName(StringRef s) {
-//     std::string name = s;
-//     ...
-//   }
-class StringRef {
- private:
-  const char *data_;
-  mutable std::size_t size_;
-
- public:
-  StringRef(const char *s, std::size_t size = 0) : data_(s), size_(size) {}
-  StringRef(const std::string &s) : data_(s.c_str()), size_(s.size()) {}
-
-  operator std::string() const { return std::string(data_, size()); }
-
-  const char *c_str() const { return data_; }
-
-  std::size_t size() const {
-    if (size_ == 0) size_ = std::strlen(data_);
-    return size_;
-  }
-};
-
 namespace internal {
 
 // This is a transient object that normally exists only as a temporary

format_test.cc

@@ -356,7 +356,7 @@ TEST(FormatterTest, Fill) {
   EXPECT_EQ("def**", str(Format("{0:*<5}") << TestString("def")));
 }
 
-TEST(FormatterTest, PlusFlag) {
+TEST(FormatterTest, PlusSign) {
   EXPECT_EQ("+42", str(Format("{0:+}") << 42));
   EXPECT_EQ("-42", str(Format("{0:+}") << -42));
   EXPECT_EQ("+42", str(Format("{0:+}") << 42));
@@ -379,6 +379,29 @@ TEST(FormatterTest, PlusFlag) {
       FormatError, "format specifier '+' requires numeric argument");
 }
 
+TEST(FormatterTest, MinusSign) {
+  EXPECT_EQ("42", str(Format("{0:-}") << 42));
+  EXPECT_EQ("-42", str(Format("{0:-}") << -42));
+  EXPECT_EQ("42", str(Format("{0:-}") << 42));
+  EXPECT_THROW_MSG(Format("{0:-}") << 42u,
+      FormatError, "format specifier '-' requires signed argument");
+  EXPECT_EQ("42", str(Format("{0:-}") << 42l));
+  EXPECT_THROW_MSG(Format("{0:-}") << 42ul,
+      FormatError, "format specifier '-' requires signed argument");
+  EXPECT_EQ("42", str(Format("{0:-}") << 42.0));
+  EXPECT_EQ("42", str(Format("{0:-}") << 42.0l));
+  EXPECT_THROW_MSG(Format("{0:-") << 'c',
+      FormatError, "unmatched '{' in format");
+  EXPECT_THROW_MSG(Format("{0:-}") << 'c',
+      FormatError, "format specifier '-' requires numeric argument");
+  EXPECT_THROW_MSG(Format("{0:-}") << "abc",
+      FormatError, "format specifier '-' requires numeric argument");
+  EXPECT_THROW_MSG(Format("{0:-}") << reinterpret_cast<void*>(0x42),
+      FormatError, "format specifier '-' requires numeric argument");
+  EXPECT_THROW_MSG(Format("{0:-}") << TestString(),
+      FormatError, "format specifier '-' requires numeric argument");
+}
+
 TEST(FormatterTest, ZeroFlag) {
   EXPECT_EQ("42", str(Format("{0:0}") << 42));
   EXPECT_EQ("-0042", str(Format("{0:05}") << -42));