tools/gn/input_conversion.cc

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "tools/gn/input_conversion.h"
   6
   7 #include "base/strings/string_split.h"
   8 #include "base/strings/string_util.h"
   9 #include "tools/gn/build_settings.h"
  10 #include "tools/gn/err.h"
  11 #include "tools/gn/input_file.h"
  12 #include "tools/gn/label.h"
  13 #include "tools/gn/parse_tree.h"
  14 #include "tools/gn/parser.h"
  15 #include "tools/gn/scheduler.h"
  16 #include "tools/gn/scope.h"
  17 #include "tools/gn/settings.h"
  18 #include "tools/gn/tokenizer.h"
  19 #include "tools/gn/value.h"
  20
  21 namespace {
  22
  23 enum ValueOrScope {
  24   PARSE_VALUE,  // Treat the input as an expression.
  25   PARSE_SCOPE,  // Treat the input as code and return the resulting scope.
  26 };
  27
  28 // Sets the origin of the value and any nested values with the given node.
  29 Value ParseValueOrScope(const Settings* settings,
  30                         const std::string& input,
  31                         ValueOrScope what,
  32                         const ParseNode* origin,
  33                         Err* err) {
  34   // The memory for these will be kept around by the input file manager
  35   // so the origin parse nodes for the values will be preserved.
  36   InputFile* input_file;
  37   std::vector<Token>* tokens;
  38   scoped_ptr<ParseNode>* parse_root_ptr;
  39   g_scheduler->input_file_manager()->AddDynamicInput(
  40       SourceFile(), &input_file, &tokens, &parse_root_ptr);
  41
  42   input_file->SetContents(input);
  43   if (origin) {
  44     // This description will be the blame for any error messages caused by
  45     // script parsing or if a value is blamed. It will say
  46     // "Error at <...>:line:char" so here we try to make a string for <...>
  47     // that reads well in this context.
  48     input_file->set_friendly_name(
  49         "dynamically parsed input that " +
  50         origin->GetRange().begin().Describe(true) +
  51         " loaded ");
  52   } else {
  53     input_file->set_friendly_name("dynamic input");
  54   }
  55
  56   *tokens = Tokenizer::Tokenize(input_file, err);
  57   if (err->has_error())
  58     return Value();
  59
  60   // Parse the file according to what we're looking for.
  61   if (what == PARSE_VALUE)
  62     *parse_root_ptr = Parser::ParseValue(*tokens, err);
  63   else
  64     *parse_root_ptr = Parser::Parse(*tokens, err);  // Will return a Block.
  65   if (err->has_error())
  66     return Value();
  67   ParseNode* parse_root = parse_root_ptr->get();  // For nicer syntax below.
  68
  69   // It's valid for the result to be a null pointer, this just means that the
  70   // script returned nothing.
  71   if (!parse_root)
  72     return Value();
  73
  74   scoped_ptr<Scope> scope(new Scope(settings));
  75   Value result = parse_root->Execute(scope.get(), err);
  76   if (err->has_error())
  77     return Value();
  78
  79   // When we want the result as a scope, the result is actually the scope
  80   // we made, rather than the result of running the block (which will be empty).
  81   if (what == PARSE_SCOPE) {
  82     DCHECK(result.type() == Value::NONE);
  83     result = Value(origin, scope.Pass());
  84   }
  85   return result;
  86 }
  87
  88 Value ParseList(const std::string& input, const ParseNode* origin, Err* err) {
  89   Value ret(origin, Value::LIST);
  90   std::vector<std::string> as_lines;
  91   base::SplitString(input, '\n', &as_lines);
  92
  93   // Trim one empty line from the end since the last line might end in a
  94   // newline. If the user wants more trimming, they'll specify "trim" in the
  95   // input conversion options.
  96   if (!as_lines.empty() && as_lines[as_lines.size() - 1].empty())
  97     as_lines.resize(as_lines.size() - 1);
  98
  99   ret.list_value().reserve(as_lines.size());
 100   for (const auto& line : as_lines)
 101     ret.list_value().push_back(Value(origin, line));
 102   return ret;
 103 }
 104
 105 // Backend for ConvertInputToValue, this takes the extracted string for the
 106 // input conversion so we can recursively call ourselves to handle the optional
 107 // "trim" prefix. This original value is also kept for the purposes of throwing
 108 // errors.
 109 Value DoConvertInputToValue(const Settings* settings,
 110                             const std::string& input,
 111                             const ParseNode* origin,
 112                             const Value& original_input_conversion,
 113                             const std::string& input_conversion,
 114                             Err* err) {
 115   if (input_conversion.empty())
 116     return Value();  // Empty string means discard the result.
 117
 118   const char kTrimPrefix[] = "trim ";
 119   if (StartsWithASCII(input_conversion, kTrimPrefix, true)) {
 120     std::string trimmed;
 121     base::TrimWhitespaceASCII(input, base::TRIM_ALL, &trimmed);
 122
 123     // Remove "trim" prefix from the input conversion and re-run.
 124     return DoConvertInputToValue(
 125         settings, trimmed, origin, original_input_conversion,
 126         input_conversion.substr(arraysize(kTrimPrefix) - 1), err);
 127   }
 128
 129   if (input_conversion == "value")
 130     return ParseValueOrScope(settings, input, PARSE_VALUE, origin, err);
 131   if (input_conversion == "string")
 132     return Value(origin, input);
 133   if (input_conversion == "list lines")
 134     return ParseList(input, origin, err);
 135   if (input_conversion == "scope")
 136     return ParseValueOrScope(settings, input, PARSE_SCOPE, origin, err);
 137
 138   *err = Err(original_input_conversion, "Not a valid input_conversion.",
 139              "Have you considered a career in retail?");
 140   return Value();
 141 }
 142
 143 }  // namespace
 144
 145 extern const char kInputConversion_Help[] =
 146     "input_conversion: Specifies how to transform input to a variable.\n"
 147     "\n"
 148     "  input_conversion is an argument to read_file and exec_script that\n"
 149     "  specifies how the result of the read operation should be converted\n"
 150     "  into a variable.\n"
 151     "\n"
 152     "  \"\" (the default)\n"
 153     "      Discard the result and return None.\n"
 154     "\n"
 155     "  \"list lines\"\n"
 156     "      Return the file contents as a list, with a string for each line.\n"
 157     "      The newlines will not be present in the result. The last line may\n"
 158     "      or may not end in a newline.\n"
 159     "\n"
 160     "      After splitting, each individual line will be trimmed of\n"
 161     "      whitespace on both ends.\n"
 162     "\n"
 163     "  \"scope\"\n"
 164     "      Execute the block as GN code and return a scope with the\n"
 165     "      resulting values in it. If the input was:\n"
 166     "        a = [ \"hello.cc\", \"world.cc\" ]\n"
 167     "        b = 26\n"
 168     "      and you read the result into a variable named \"val\", then you\n"
 169     "      could access contents the \".\" operator on \"val\":\n"
 170     "        sources = val.a\n"
 171     "        some_count = val.b\n"
 172     "\n"
 173     "  \"string\"\n"
 174     "      Return the file contents into a single string.\n"
 175     "\n"
 176     "  \"value\"\n"
 177     "      Parse the input as if it was a literal rvalue in a buildfile.\n"
 178     "      Examples of typical program output using this mode:\n"
 179     "        [ \"foo\", \"bar\" ]     (result will be a list)\n"
 180     "      or\n"
 181     "        \"foo bar\"            (result will be a string)\n"
 182     "      or\n"
 183     "        5                    (result will be an integer)\n"
 184     "\n"
 185     "      Note that if the input is empty, the result will be a null value\n"
 186     "      which will produce an error if assigned to a variable.\n"
 187     "\n"
 188     "  \"trim ...\"\n"
 189     "      Prefixing any of the other transformations with the word \"trim\"\n"
 190     "      will result in whitespace being trimmed from the beginning and end\n"
 191     "      of the result before processing.\n"
 192     "\n"
 193     "      Examples: \"trim string\" or \"trim list lines\"\n"
 194     "\n"
 195     "      Note that \"trim value\" is useless because the value parser skips\n"
 196     "      whitespace anyway.\n";
 197
 198 Value ConvertInputToValue(const Settings* settings,
 199                           const std::string& input,
 200                           const ParseNode* origin,
 201                           const Value& input_conversion_value,
 202                           Err* err) {
 203   if (input_conversion_value.type() == Value::NONE)
 204     return Value();  // Allow null inputs to mean discard the result.
 205   if (!input_conversion_value.VerifyTypeIs(Value::STRING, err))
 206     return Value();
 207   return DoConvertInputToValue(settings, input, origin, input_conversion_value,
 208                                input_conversion_value.string_value(), err);
 209 }