Rename FileDataLoader::From to ::from (#381)

Summary:
Pull Request resolved: #381

This is a commonly-used method that violates our style guide.
ghstack-source-id: 200971163
exported-using-ghexport

Reviewed By: cccclai

Differential Revision: D49351745

fbshipit-source-id: 7f3a6b7f02db5357a0fb97f71e9695077734f2ac

extension/data_loader/file_data_loader.cpp

@@ -59,7 +59,7 @@ FileDataLoader::~FileDataLoader() {
   ::close(fd_);
 }
 
-Result<FileDataLoader> FileDataLoader::From(
+Result<FileDataLoader> FileDataLoader::from(
     const char* file_name,
     size_t alignment) {
   ET_CHECK_OR_RETURN_ERROR(

extension/data_loader/file_data_loader.h

@@ -40,10 +40,17 @@ class FileDataLoader : public DataLoader {
    *     could not be found.
    * @retval Error::MemoryAllocationFailed Internal memory allocation failure.
    */
-  static Result<FileDataLoader> From(
+  static Result<FileDataLoader> from(
       const char* file_name,
       size_t alignment = alignof(std::max_align_t));
 
+  /// DEPRECATED: Use the lowercase `from()` instead.
+  __ET_DEPRECATED static Result<FileDataLoader> From(
+      const char* file_name,
+      size_t alignment = alignof(std::max_align_t)) {
+    return from(file_name, alignment);
+  }
+
   // Movable to be compatible with Result.
   FileDataLoader(FileDataLoader&& rhs) noexcept
       : file_name_(rhs.file_name_),

extension/data_loader/test/file_data_loader_test.cpp

@@ -49,7 +49,7 @@ TEST_P(FileDataLoaderTest, InBoundsLoadsSucceed) {
 
   // Wrap it in a loader.
   Result<FileDataLoader> fdl =
-      FileDataLoader::From(tf.path().c_str(), alignment());
+      FileDataLoader::from(tf.path().c_str(), alignment());
   ASSERT_EQ(fdl.error(), Error::Ok);
 
   // size() should succeed and reflect the total size.
@@ -113,7 +113,7 @@ TEST_P(FileDataLoaderTest, OutOfBoundsLoadFails) {
   TempFile tf(data, sizeof(data));
 
   Result<FileDataLoader> fdl =
-      FileDataLoader::From(tf.path().c_str(), alignment());
+      FileDataLoader::from(tf.path().c_str(), alignment());
   ASSERT_EQ(fdl.error(), Error::Ok);
 
   // Loading beyond the end of the data should fail.
@@ -133,7 +133,7 @@ TEST_P(FileDataLoaderTest, OutOfBoundsLoadFails) {
 
 TEST_P(FileDataLoaderTest, FromMissingFileFails) {
   // Wrapping a file that doesn't exist should fail.
-  Result<FileDataLoader> fdl = FileDataLoader::From(
+  Result<FileDataLoader> fdl = FileDataLoader::from(
       "/tmp/FILE_DOES_NOT_EXIST_EXECUTORCH_MMAP_LOADER_TEST");
   EXPECT_NE(fdl.error(), Error::Ok);
 }
@@ -145,15 +145,15 @@ TEST_P(FileDataLoaderTest, BadAlignmentFails) {
 
   // Creating a loader with default alignment works fine.
   {
-    Result<FileDataLoader> fdl = FileDataLoader::From(tf.path().c_str());
+    Result<FileDataLoader> fdl = FileDataLoader::from(tf.path().c_str());
     ASSERT_EQ(fdl.error(), Error::Ok);
   }
 
   // Bad alignments fail.
   const std::vector<size_t> bad_alignments = {0, 3, 5, 17};
   for (size_t bad_alignment : bad_alignments) {
     Result<FileDataLoader> fdl =
-        FileDataLoader::From(tf.path().c_str(), bad_alignment);
+        FileDataLoader::from(tf.path().c_str(), bad_alignment);
     ASSERT_EQ(fdl.error(), Error::InvalidArgument);
   }
 }
@@ -164,7 +164,7 @@ TEST_P(FileDataLoaderTest, MoveCtor) {
   std::string contents = "FILE_CONTENTS";
   TempFile tf(contents);
   Result<FileDataLoader> fdl =
-      FileDataLoader::From(tf.path().c_str(), alignment());
+      FileDataLoader::from(tf.path().c_str(), alignment());
   ASSERT_EQ(fdl.error(), Error::Ok);
   EXPECT_EQ(fdl->size().get(), contents.size());
 
@@ -184,6 +184,26 @@ TEST_P(FileDataLoaderTest, MoveCtor) {
   EXPECT_EQ(0, std::memcmp(fb->data(), contents.data(), fb->size()));
 }
 
+// Test that the deprecated From method (capital 'F') still works.
+TEST_P(FileDataLoaderTest, DEPRECATEDFrom) {
+  // Write some heterogeneous data to a file.
+  uint8_t data[256];
+  for (int i = 0; i < sizeof(data); ++i) {
+    data[i] = i;
+  }
+  TempFile tf(data, sizeof(data));
+
+  // Wrap it in a loader.
+  Result<FileDataLoader> fdl =
+      FileDataLoader::From(tf.path().c_str(), alignment());
+  ASSERT_EQ(fdl.error(), Error::Ok);
+
+  // size() should succeed and reflect the total size.
+  Result<size_t> size = fdl->size();
+  ASSERT_EQ(size.error(), Error::Ok);
+  EXPECT_EQ(*size, sizeof(data));
+}
+
 // Run all FileDataLoaderTests multiple times, varying the return value of
 // `GetParam()` based on the `testing::Values` list. The tests will interpret
 // the value as "alignment".