Merge "Check Errorf()/ErrnoErrorf() format string at compile time"

base/include/android-base/result.h

@@ -156,11 +156,11 @@ class Error {
   Error& operator=(const Error&) = delete;
   Error& operator=(Error&&) = delete;
 
-  template <typename... Args>
-  friend Error Errorf(const char* fmt, const Args&... args);
+  template <typename T, typename... Args>
+  friend Error ErrorfImpl(const T&& fmt, const Args&... args);
 
-  template <typename... Args>
-  friend Error ErrnoErrorf(const char* fmt, const Args&... args);
+  template <typename T, typename... Args>
+  friend Error ErrnoErrorfImpl(const T&& fmt, const Args&... args);
 
  private:
   Error(bool append_errno, int errno_to_append, const std::string& message)
@@ -191,16 +191,24 @@ inline int ErrorCode(int code, T&& t, const Args&... args) {
   return ErrorCode(code, args...);
 }
 
-template <typename... Args>
-inline Error Errorf(const char* fmt, const Args&... args) {
+// TODO(tomcherry): Remove this once we've removed all `using android::base::Errorf` and `using
+// android::base::ErrnoErrorf` lines.
+enum Errorf {};
+enum ErrnoErrorf {};
+
+template <typename T, typename... Args>
+inline Error ErrorfImpl(const T&& fmt, const Args&... args) {
   return Error(false, ErrorCode(0, args...), fmt::format(fmt, args...));
 }
 
-template <typename... Args>
-inline Error ErrnoErrorf(const char* fmt, const Args&... args) {
+template <typename T, typename... Args>
+inline Error ErrnoErrorfImpl(const T&& fmt, const Args&... args) {
   return Error(true, errno, fmt::format(fmt, args...));
 }
 
+#define Errorf(fmt, ...) android::base::ErrorfImpl(FMT_STRING(fmt), ##__VA_ARGS__)
+#define ErrnoErrorf(fmt, ...) android::base::ErrnoErrorfImpl(FMT_STRING(fmt), ##__VA_ARGS__)
+
 template <typename T>
 using Result = android::base::expected<T, ResultError>;
 

base/result_test.cpp

@@ -362,7 +362,7 @@ TEST(result, error_with_fmt) {
   result = Errorf("{} {}!", std::string("hello"), std::string("world"));
   EXPECT_EQ("hello world!", result.error().message());
 
-  result = Errorf("{h} {w}!", fmt::arg("w", "world"), fmt::arg("h", "hello"));
+  result = Errorf("{1} {0}!", "world", "hello");
   EXPECT_EQ("hello world!", result.error().message());
 
   result = Errorf("hello world!");

init/result.h

@@ -22,8 +22,6 @@
 #include <android-base/result.h>
 
 using android::base::ErrnoError;
-using android::base::ErrnoErrorf;
 using android::base::Error;
-using android::base::Errorf;
 using android::base::Result;
 using android::base::ResultError;