Refactor GN source expansions.

tools/gn/substitution_writer.cc

Index: tools/gn/substitution_writer.cc
diff --git a/tools/gn/substitution_writer.cc b/tools/gn/substitution_writer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0738b6f7e0a070fa23092ea6049fb65e26e85e36
--- /dev/null
+++ b/tools/gn/substitution_writer.cc
@@ -0,0 +1,317 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "tools/gn/substitution_writer.h"
+
+#include "tools/gn/build_settings.h"
+#include "tools/gn/escape.h"
+#include "tools/gn/filesystem_utils.h"
+#include "tools/gn/output_file.h"
+#include "tools/gn/settings.h"
+#include "tools/gn/source_file.h"
+#include "tools/gn/substitution_list.h"
+#include "tools/gn/substitution_pattern.h"
+
+const char kSourceExpansion_Help[] =
+    "How Source Expansion Works\n"
+    "\n"
+    "  Source expansion is used for the action_foreach and copy target types\n"
+    "  to map source file names to output file names or arguments.\n"
+    "\n"
+    "  To perform source expansion in the outputs, GN maps every entry in the\n"
+    "  sources to every entry in the outputs list, producing the cross\n"
+    "  product of all combinations, expanding placeholders (see below).\n"
+    "\n"
+    "  Source expansion in the args works similarly, but performing the\n"
+    "  placeholder substitution produces a different set of arguments for\n"
+    "  each invocation of the script.\n"
+    "\n"
+    "  If no placeholders are found, the outputs or args list will be treated\n"
+    "  as a static list of literal file names that do not depend on the\n"
+    "  sources.\n"
+    "\n"
+    "  See \"gn help copy\" and \"gn help action_foreach\" for more on how\n"
+    "  this is applied.\n"
+    "\n"
+    "Placeholders\n"
+    "\n"
+    "  {{source}}\n"
+    "      The name of the source file including directory (*). This will\n"
+    "      generally be used for specifying inputs to a script in the\n"
+    "      \"args\" variable.\n"
+    "        \"//foo/bar/baz.txt\" => \"../../foo/bar/baz.txt\"\n"
+    "\n"
+    "  {{source_file_part}}\n"
+    "      The file part of the source including the extension.\n"
+    "        \"//foo/bar/baz.txt\" => \"baz.txt\"\n"
+    "\n"
+    "  {{source_name_part}}\n"
+    "      The filename part of the source file with no directory or\n"
+    "      extension. This will generally be used for specifying a\n"
+    "      transformation from a soruce file to a destination file with the\n"
+    "      same name but different extension.\n"
+    "        \"//foo/bar/baz.txt\" => \"baz\"\n"
+    "\n"
+    "  {{source_dir}}\n"
+    "      The directory (*) containing the source file with no\n"
+    "      trailing slash.\n"
+    "        \"//foo/bar/baz.txt\" => \"../../foo/bar\"\n"
+    "\n"
+    "  {{source_root_relative_dir}}\n"
+    "      The path to the source file's directory relative to the source\n"
+    "      root, with no leading \"//\" or trailing slashes. If the path is\n"
+    "      system-absolute, (beginning in a single slash) this will just\n"
+    "      return the path with no trailing slash. This value will always\n"
+    "      be the same, regardless of whether it appears in the \"outputs\"\n"
+    "      or \"args\" section.\n"
+    "        \"//foo/bar/baz.txt\" => \"foo/bar\"\n"
+    "\n"
+    "  {{source_gen_dir}}\n"
+    "      The generated file directory (*) corresponding to the source\n"
+    "      file's path. This will be different than the target's generated\n"
+    "      file directory if the source file is in a different directory\n"
+    "      than the BUILD.gn file.\n"
+    "        \"//foo/bar/baz.txt\" => \"gen/foo/bar\"\n"
+    "\n"
+    "  {{source_out_dir}}\n"
+    "      The object file directory (*) corresponding to the source file's\n"
+    "      path, relative to the build directory. this us be different than\n"
+    "      the target's out directory if the source file is in a different\n"
+    "      directory than the build.gn file.\n"
+    "        \"//foo/bar/baz.txt\" => \"obj/foo/bar\"\n"
+    "\n"
+    "(*) Note on directories\n"
+    "\n"
+    "  Paths containing directories (except the source_root_relative_dir)\n"
+    "  will be different depending on what context the expansion is evaluated\n"
+    "  in. Generally it should \"just work\" but it means you can't\n"
+    "  concatenate strings containing these values with reasonable results.\n"
+    "\n"
+    "  Details: source expansions can be used in the \"outputs\" variable,\n"
+    "  the \"args\" variable, and in calls to \"process_file_template\". The\n"
+    "  \"args\" are passed to a script which is run from the build directory,\n"
+    "  so these directories will relative to the build directory for the\n"
+    "  script to find. In the other cases, the directories will be source-\n"
+    "  absolute (begin with a \"//\") because the results of those expansions\n"
+    "  will be handled by GN internally.\n"
+    "\n"
+    "Examples\n"
+    "\n"
+    "  Non-varying outputs:\n"
+    "    action(\"hardcoded_outputs\") {\n"
+    "      sources = [ \"input1.idl\", \"input2.idl\" ]\n"
+    "      outputs = [ \"$target_out_dir/output1.dat\",\n"
+    "                  \"$target_out_dir/output2.dat\" ]\n"
+    "    }\n"
+    "  The outputs in this case will be the two literal files given.\n"
+    "\n"
+    "  Varying outputs:\n"
+    "    action_foreach(\"varying_outputs\") {\n"
+    "      sources = [ \"input1.idl\", \"input2.idl\" ]\n"
+    "      outputs = [ \"{{source_gen_dir}}/{{source_name_part}}.h\",\n"
+    "                  \"{{source_gen_dir}}/{{source_name_part}}.cc\" ]\n"
+    "    }\n"
+    "  Performing source expansion will result in the following output names:\n"
+    "    //out/Debug/obj/mydirectory/input1.h\n"
+    "    //out/Debug/obj/mydirectory/input1.cc\n"
+    "    //out/Debug/obj/mydirectory/input2.h\n"
+    "    //out/Debug/obj/mydirectory/input2.cc\n";
+
+SubstitutionWriter::SubstitutionWriter() {
+}
+
+SubstitutionWriter::~SubstitutionWriter() {
+}
+
+// static
+SourceFile SubstitutionWriter::ApplyPatternToSource(
+      const Settings* settings,
+      const SubstitutionPattern& pattern,
+      const SourceFile& source) {
+  std::string result_value;
+  for (size_t i = 0; i < pattern.ranges().size(); i++) {
+    const SubstitutionPattern::Subrange& subrange = pattern.ranges()[i];
+    if (subrange.type == SUBSTITUTION_LITERAL) {
+      result_value.append(subrange.literal);
+    } else {
+      result_value.append(
+          GetSourceSubstitution(settings, source, subrange.type,
+                                OUTPUT_ABSOLUTE, SourceDir()));
+    }
+  }
+  CHECK(!result_value.empty() && result_value[0] == '/')
+      << "The result of the pattern \""
+      << pattern.AsString()
+      << "\" was not a path beginning in \"/\" or \"//\".";
+  return SourceFile(SourceFile::SWAP_IN, &result_value);
+}
+
+// static
+OutputFile SubstitutionWriter::ApplyPatternToSourceAsOutputFile(
+    const Settings* settings,
+    const SubstitutionPattern& pattern,
+    const SourceFile& source) {
+  SourceFile result_as_source = ApplyPatternToSource(settings, pattern, source);
+  CHECK(result_as_source.is_source_absolute())
+      << "The result of the pattern \""
+      << pattern.AsString()
+      << "\" was not an absolute path beginning in \"//\".";
+  return OutputFile(
+      RebaseSourceAbsolutePath(result_as_source.value(),
+                               settings->build_settings()->build_dir()));
+}
+
+// static
+void SubstitutionWriter::ApplyListToSource(
+    const Settings* settings,
+    const SubstitutionList& list,
+    const SourceFile& source,
+    std::vector<SourceFile>* output) {
+  for (size_t i = 0; i < list.list().size(); i++) {
+    output->push_back(ApplyPatternToSource(
+        settings, list.list()[i], source));
+  }
+}
+
+// static
+void SubstitutionWriter::ApplyListToSourceAsOutputFile(
+    const Settings* settings,
+    const SubstitutionList& list,
+    const SourceFile& source,
+    std::vector<OutputFile>* output) {
+  for (size_t i = 0; i < list.list().size(); i++) {
+    output->push_back(ApplyPatternToSourceAsOutputFile(
+        settings, list.list()[i], source));
+  }
+}
+
+// static
+void SubstitutionWriter::ApplyListToSources(
+    const Settings* settings,
+    const SubstitutionList& list,
+    const std::vector<SourceFile>& sources,
+    std::vector<SourceFile>* output) {
+  output->clear();
+  for (size_t i = 0; i < sources.size(); i++)
+    ApplyListToSource(settings, list, sources[i], output);
+}
+
+// static
+void SubstitutionWriter::ApplyListToSourcesAsOutputFile(
+    const Settings* settings,
+    const SubstitutionList& list,
+    const std::vector<SourceFile>& sources,
+    std::vector<OutputFile>* output) {
+  output->clear();
+  for (size_t i = 0; i < sources.size(); i++)
+    ApplyListToSourceAsOutputFile(settings, list, sources[i], output);
+}
+
+// static
+void SubstitutionWriter::WriteNinjaVariablesForSource(
+    const Settings* settings,
+    const SourceFile& source,
+    const std::vector<SubstitutionType>& types,
+    const EscapeOptions& escape_options,
+    std::ostream& out) {
+  for (size_t i = 0; i < types.size(); i++) {
+    // Don't write SOURCE since that just maps to Ninja's $in variable, which
+    // is implicit in the rule.
+    if (types[i] != SUBSTITUTION_SOURCE) {
+      out << "  " << kSubstitutionNinjaNames[types[i]] << " = ";
+        EscapeStringToStream(
+            out,
+            GetSourceSubstitution(settings, source, types[i], OUTPUT_RELATIVE,
+                                  settings->build_settings()->build_dir()),
+            escape_options);
+      out << std::endl;
+    }
+  }
+}
+
+// static
+void SubstitutionWriter::WriteWithNinjaVariables(
+    const SubstitutionPattern& pattern,
+    const EscapeOptions& escape_options,
+    std::ostream& out) {
+  // The result needs to be quoted as if it was one string, but the $ for
+  // the inserted Ninja variables can't be escaped. So write to a buffer with
+  // no quoting, and then quote the whole thing if necessary.
+  EscapeOptions no_quoting(escape_options);
+  no_quoting.inhibit_quoting = true;
+
+  bool needs_quotes = false;
+  std::string result;
+  for (size_t i = 0; i < pattern.ranges().size(); i++) {
+    const SubstitutionPattern::Subrange range = pattern.ranges()[i];
+    if (range.type == SUBSTITUTION_LITERAL) {
+      result.append(EscapeString(range.literal, no_quoting, &needs_quotes));
+    } else {
+      result.append("${");
+      result.append(kSubstitutionNinjaNames[range.type]);
+      result.append("}");
+    }
+  }
+
+  if (needs_quotes && !escape_options.inhibit_quoting)
+    out << "\"" << result << "\"";
+  else
+    out << result;
+}
+
+// static
+std::string SubstitutionWriter::GetSourceSubstitution(
+    const Settings* settings,
+    const SourceFile& source,
+    SubstitutionType type,
+    OutputStyle output_style,
+    const SourceDir& relative_to) {
+  std::string to_rebase;
+  switch (type) {
+    case SUBSTITUTION_SOURCE:
+      if (source.is_system_absolute())
+        return source.value();
+      to_rebase = source.value();
+      break;
+
+    case SUBSTITUTION_SOURCE_NAME_PART:
+      return FindFilenameNoExtension(&source.value()).as_string();
+
+    case SUBSTITUTION_SOURCE_FILE_PART:
+      return source.GetName();
+
+    case SUBSTITUTION_SOURCE_DIR:
+      if (source.is_system_absolute())
+        return DirectoryWithNoLastSlash(source.GetDir());
+      to_rebase = DirectoryWithNoLastSlash(source.GetDir());
+      break;
+
+    case SUBSTITUTION_SOURCE_ROOT_RELATIVE_DIR:
+      if (source.is_system_absolute())
+        return DirectoryWithNoLastSlash(source.GetDir());
+      return RebaseSourceAbsolutePath(
+          DirectoryWithNoLastSlash(source.GetDir()), SourceDir("//"));
+
+    case SUBSTITUTION_SOURCE_GEN_DIR:
+      to_rebase = DirectoryWithNoLastSlash(
+          GetGenDirForSourceDir(settings, source.GetDir()));
+      break;
+
+    case SUBSTITUTION_SOURCE_OUT_DIR:
+      to_rebase = DirectoryWithNoLastSlash(
+          GetOutputDirForSourceDir(settings, source.GetDir()));
+      break;
+
+    default:
+      NOTREACHED();
+      return std::string();
+  }
+
+  // If we get here, the result is a path that should be made relative or
+  // absolute according to the output_style. Other cases (just file name or
+  // extension extraction) will have been handled via early return above.
+  if (output_style == OUTPUT_ABSOLUTE)
+    return to_rebase;
+  return RebaseSourceAbsolutePath(to_rebase, relative_to);
+}