text: // Copyright (c) 2013 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/input_conversion.h"
  
  #include "base/strings/string_split.h"
  #include "base/strings/string_util.h"
  #include "tools/gn/build_settings.h"
  #include "tools/gn/err.h"
  #include "tools/gn/input_file.h"
  #include "tools/gn/label.h"
  #include "tools/gn/parse_tree.h"
  #include "tools/gn/parser.h"
  #include "tools/gn/scheduler.h"
  #include "tools/gn/scope.h"
  #include "tools/gn/settings.h"
  #include "tools/gn/tokenizer.h"
  #include "tools/gn/value.h"
  
  namespace {
  
  enum ValueOrScope {
    PARSE_VALUE,  // Treat the input as an expression.
    PARSE_SCOPE,  // Treat the input as code and return the resulting scope.
  };
  
  // Sets the origin of the value and any nested values with the given node.
  Value ParseValueOrScope(const Settings* settings,
                          const std::string& input,
                          ValueOrScope what,
                          const ParseNode* origin,
                          Err* err) {
    // The memory for these will be kept around by the input file manager
    // so the origin parse nodes for the values will be preserved.
    InputFile* input_file;
    std::vector<Token>* tokens;
    scoped_ptr<ParseNode>* parse_root_ptr;
    g_scheduler->input_file_manager()->AddDynamicInput(
        &input_file, &tokens, &parse_root_ptr);
  
    input_file->SetContents(input);
    if (origin) {
      // This description will be the blame for any error messages caused by
      // script parsing or if a value is blamed. It will say
      // "Error at <...>:line:char" so here we try to make a string for <...>
      // that reads well in this context.
      input_file->set_friendly_name(
          "dynamically parsed input that " +
          origin->GetRange().begin().Describe(true) +
          " loaded ");
    } else {
      input_file->set_friendly_name("dynamic input");
    }
  
    *tokens = Tokenizer::Tokenize(input_file, err);
    if (err->has_error())
      return Value();
  
    // Parse the file according to what we're looking for.
    if (what == PARSE_VALUE)
      *parse_root_ptr = Parser::ParseExpression(*tokens, err);
    else
      *parse_root_ptr = Parser::Parse(*tokens, err);  // Will return a Block.
    if (err->has_error())
      return Value();
    ParseNode* parse_root = parse_root_ptr->get();  // For nicer syntax below.
  
    // It's valid for the result to be a null pointer, this just means that the
    // script returned nothing.
    if (!parse_root)
      return Value();
  
    // When parsing as a value, the result should either be a list or a literal,
    // anything else is invalid.
    if (what == PARSE_VALUE) {
      if (!parse_root->AsList() && !parse_root->AsLiteral())
        return Value();
    }
  
    scoped_ptr<Scope> scope(new Scope(settings));
  
    Value result = parse_root->Execute(scope.get(), err);
    if (err->has_error())
      return Value();
  
    // When we want the result as a scope, the result is actually the scope
    // we made, rather than the result of running the block (which will be empty).
    if (what == PARSE_SCOPE) {
      DCHECK(result.type() == Value::NONE);
      result = Value(origin, scope.Pass());
    }
    return result;
  }
  
  Value ParseList(const std::string& input, const ParseNode* origin, Err* err) {
    Value ret(origin, Value::LIST);
    std::vector<std::string> as_lines;
    base::SplitString(input, '\n', &as_lines);
  
    // Trim one empty line from the end since the last line might end in a
    // newline. If the user wants more trimming, they'll specify "trim" in the
    // input conversion options.
    if (!as_lines.empty() && as_lines[as_lines.size() - 1].empty())
      as_lines.resize(as_lines.size() - 1);
  
    ret.list_value().reserve(as_lines.size());
    for (size_t i = 0; i < as_lines.size(); i++)
      ret.list_value().push_back(Value(origin, as_lines[i]));
    return ret;
  }
  
  // Backend for ConvertInputToValue, this takes the extracted string for the
  // input conversion so we can recursively call ourselves to handle the optional
  // "trim" prefix. This original value is also kept for the purposes of throwing
  // errors.
  Value DoConvertInputToValue(const Settings* settings,
                              const std::string& input,
                              const ParseNode* origin,
                              const Value& original_input_conversion,
                              const std::string& input_conversion,
                              Err* err) {
    if (input_conversion.empty())
      return Value();  // Empty string means discard the result.
  
    const char kTrimPrefix[] = "trim ";
    if (StartsWithASCII(input_conversion, kTrimPrefix, true)) {
      std::string trimmed;
      base::TrimWhitespaceASCII(input, base::TRIM_ALL, &trimmed);
  
      // Remove "trim" prefix from the input conversion and re-run.
      return DoConvertInputToValue(
          settings, trimmed, origin, original_input_conversion,
          input_conversion.substr(arraysize(kTrimPrefix) - 1), err);
    }
  
    if (input_conversion == "value")
      return ParseValueOrScope(settings, input, PARSE_VALUE, origin, err);
    if (input_conversion == "string")
      return Value(origin, input);
    if (input_conversion == "list lines")
      return ParseList(input, origin, err);
    if (input_conversion == "scope")
      return ParseValueOrScope(settings, input, PARSE_SCOPE, origin, err);
  
    *err = Err(original_input_conversion, "Not a valid input_conversion.",
               "Have you considered a career in retail?");
    return Value();
  }
  
  }  // namespace
  
  extern const char kInputConversion_Help[] =
      "input_conversion: Specifies how to transform input to a variable.\n"
      "\n"
      "  input_conversion is an argument to read_file and exec_script that\n"
      "  specifies how the result of the read operation should be converted\n"
      "  into a variable.\n"
      "\n"
      "  \"\" (the default)\n"
      "      Discard the result and return None.\n"
      "\n"
      "  \"list lines\"\n"
      "      Return the file contents as a list, with a string for each line.\n"
      "      The newlines will not be present in the result. The last line may\n"
      "      or may not end in a newline.\n"
      "\n"
      "      After splitting, each individual line will be trimmed of\n"
      "      whitespace on both ends.\n"
      "\n"
      "  \"scope\"\n"
      "      Execute the block as GN code and return a scope with the\n"
      "      resulting values in it. If the input was:\n"
      "        a = [ \"hello.cc\", \"world.cc\" ]\n"
      "        b = 26\n"
      "      and you read the result into a variable named \"val\", then you\n"
      "      could access contents the \".\" operator on \"val\":\n"
      "        sources = val.a\n"
      "        some_count = val.b\n"
      "\n"
      "  \"string\"\n"
      "      Return the file contents into a single string.\n"
      "\n"
      "  \"value\"\n"
      "      Parse the input as if it was a literal rvalue in a buildfile.\n"
      "      Examples of typical program output using this mode:\n"
      "        [ \"foo\", \"bar\" ]     (result will be a list)\n"
      "      or\n"
      "        \"foo bar\"            (result will be a string)\n"
      "      or\n"
      "        5                    (result will be an integer)\n"
      "\n"
      "      Note that if the input is empty, the result will be a null value\n"
      "      which will produce an error if assigned to a variable.\n"
      "\n"
      "  \"trim ...\"\n"
      "      Prefixing any of the other transformations with the word \"trim\"\n"
      "      will result in whitespace being trimmed from the beginning and end\n"
      "      of the result before processing.\n"
      "\n"
      "      Examples: \"trim string\" or \"trim list lines\"\n"
      "\n"
      "      Note that \"trim value\" is useless because the value parser skips\n"
      "      whitespace anyway.\n";
  
  Value ConvertInputToValue(const Settings* settings,
                            const std::string& input,
                            const ParseNode* origin,
                            const Value& input_conversion_value,
                            Err* err) {
    if (input_conversion_value.type() == Value::NONE)
      return Value();  // Allow null inputs to mean discard the result.
    if (!input_conversion_value.VerifyTypeIs(Value::STRING, err))
      return Value();
    return DoConvertInputToValue(settings, input, origin, input_conversion_value,
                                 input_conversion_value.string_value(), err);
  }
  