rewrite the GetOuputFileName(), add tests, update blurbs

glslc/src/file_compiler.cc

@@ -198,32 +198,77 @@ std::string GetBaseNameFromAbsolutePath(const std::string& path) {
 }  // anonymous namespace
 
 std::string FileCompiler::GetOutputFileName(std::string input_filename) {
-  std::string output_file = "a.spv";
-  if (!needs_linking_) {
-    if (IsStageFile(input_filename)) {
-      output_file = input_filename + file_extension_;
+  std::string default_output_file = "a.spv";
+
+  if(needs_linking_) {
+    // When linking enabled, ignore -working-directory for output, And don't
+    // induce output file name from input file name.
+    if (output_file_name_.empty()) {
+      // no '-o' argument specified, return the default output file name.
+      // e.g. glslc shader.vert
+      //      => a.spv in <curdir>/
+      return default_output_file;
     } else {
-      output_file = input_filename.substr(0, input_filename.find_last_of('.')) +
-                    file_extension_;
+      // If '-o' specified, use the argument as output file name, no matter
+      // relative path or absolute path it is.
+      // e.g. glslc shader.vert -o output.spv
+      //      => output.spv in <curdir>/
+      return output_file_name_.str();
     }
-  }
-  if (!output_file_name_.empty()) output_file = output_file_name_.str();
-  if (!needs_linking_ && !workdir_.empty() &&
-      // If the specified output file name is an absolute path, don't refer to
-      // working directory for the output.
-      !shaderc_util::IsAbsolutePath(output_file_name_.str())) {
-    // If the input file name is an absolute path, we will have output_file as
-    // an absolute path here. So we need to get the base name of it, and refer
-    // to the working directory for the output.
-    if (shaderc_util::IsAbsolutePath(output_file)) {
-      // Get the file name from the absolute path of the input file.
-      // This is because we need to prepend working directory to the output file
-      // name to get the output file path.
-      output_file = GetBaseNameFromAbsolutePath(output_file);
+  } else {
+    // When linking is disable, should refer to -working-directory when the
+    // '-o' argument is a relative path or unspecified. If the '-o' argument
+    // is an absolute path, ignore the -working-directory for output.
+    if (output_file_name_.empty()) {
+      // No '-o' specified, use the input file names to induce the output file
+      // names.
+      // e.g. shader.vert => shader.spv or shader.s
+      //      shader.unknown => shader.spv or shader.s
+      //      shader => shader.spv or shader.s
+      std::string induced_file_name;
+      if (IsStageFile(input_filename)) {
+        induced_file_name = input_filename + file_extension_;
+      } else {
+        induced_file_name =
+            input_filename.substr(0, input_filename.find_last_of('.')) +
+            file_extension_;
+      }
+
+      if (workdir_.empty()) {
+        // no -working-directory specified
+        // e.g. glslc shader.vert -c
+        //      => shader.spv in <curdir>/
+        //      glslc /usr/local/shader.vert -c
+        //      => shader.spv in /usr/local/shader/
+        return induced_file_name;
+      } else {
+        // Case: -c/-S -working-directory=<some_dir> <input>
+        // e.g. glslc shader.vert -c -working-directory subdir
+        //      => shader.spv in <curdir>/subdir/
+        //
+        //      glslc /usr/local/shader.vert -c -working-directory subdir
+        //      => shader.spv in <curdir>/subdir/
+        if (shaderc_util::IsAbsolutePath(induced_file_name)) {
+          induced_file_name = GetBaseNameFromAbsolutePath(induced_file_name);
+        }
+        return workdir_ + induced_file_name;
+      }
+    } else {
+      // Case: -c/-S <abspath input>
+      // '-o' specified. If the argument is an absolute path, use it, if not,
+      // refer to the working directory.
+      // e.g. glslc shader.vert -c -o output.x -working-dir subdir
+      //      => output.x in <curdir>/subdir/
+      //
+      //      glslc shadser.vert -c -o /usr/local/output.x -working-dir subdir
+      //      => output.x in /usr/local/
+      if (shaderc_util::IsAbsolutePath(output_file_name_.str())) {
+        return output_file_name_.str();
+      } else {
+        return workdir_ + output_file_name_.str();
+      }
     }
-    output_file = workdir_ + output_file;
   }
-  return output_file;
 }
 
 }  // namesapce glslc

glslc/src/file_compiler.h

@@ -99,7 +99,28 @@ class FileCompiler {
   // compiler_.CompileGlslToSpv().
   shaderc::CompileOptions options_;
 
-  // Returns the name of the output file, given the input_filename string.
+  // Returns the name of the output file, computed as follows.
+  //
+  // Let "target directory" be the user-specified working directory, if
+  // provided, and the current working directory otherwise.
+  // Let "result extension" be ".spv" when generating a SPIR-V binary, and
+  // ".s" when generating SPIR-V assembly text.
+  // Let "resolved input filename" be the input filename if it's absolute,
+  // or the input filename relative to the target directory otherwise.
+  //
+  // If the user specified an output filename, then:
+  //   If the specified output filename is an absolute path, then return that.
+  //   Otherwise, return the specified output filename relative to the target
+  //   directory.
+  // If the user did not specify an output filename, then:
+  //   If linking is performed, return "a.spv" relative to the target
+  //   directory.
+  //   Derive the output filename from the input filename as follows:
+  //     If the input filename has a standard stage extension (e.g. .vert)
+  //     then return the resolved input filename but add the result extension.
+  //     Otherwise, return the resolved input filename but where its extension
+  //     is replaced with the result extension.  (If the resolved input filename
+  //     does not have an extension, then append the result extension.)
   std::string GetOutputFileName(std::string input_filename);
 
   // Resolves relative paths against this working directory. Must always end