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::ParseExpression(*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   // When parsing as a value, the result should either be a list or a literal,
  75   // anything else is invalid.
  76   if (what == PARSE_VALUE) {
  77     if (!parse_root->AsList() && !parse_root->AsLiteral())
  78       return Value();
  79   }
  80
  81   scoped_ptr<Scope> scope(new Scope(settings));
  82
  83   Value result = parse_root->Execute(scope.get(), err);
  84   if (err->has_error())
  85     return Value();
  86
  87   // When we want the result as a scope, the result is actually the scope
  88   // we made, rather than the result of running the block (which will be empty).
  89   if (what == PARSE_SCOPE) {
  90     DCHECK(result.type() == Value::NONE);
  91     result = Value(origin, scope.Pass());
  92   }
  93   return result;
  94 }
  95
  96 Value ParseList(const std::string& input, const ParseNode* origin, Err* err) {
  97   Value ret(origin, Value::LIST);
  98   std::vector<std::string> as_lines;
  99   base::SplitString(input, '\n', &as_lines);
 100
 101   // Trim one empty line from the end since the last line might end in a
 102   // newline. If the user wants more trimming, they'll specify "trim" in the
 103   // input conversion options.
 104   if (!as_lines.empty() && as_lines[as_lines.size() - 1].empty())
 105     as_lines.resize(as_lines.size() - 1);
 106
 107   ret.list_value().reserve(as_lines.size());
 108   for (size_t i = 0; i < as_lines.size(); i++)
 109     ret.list_value().push_back(Value(origin, as_lines[i]));
 110   return ret;
 111 }
 112
 113 // Backend for ConvertInputToValue, this takes the extracted string for the
 114 // input conversion so we can recursively call ourselves to handle the optional
 115 // "trim" prefix. This original value is also kept for the purposes of throwing
 116 // errors.
 117 Value DoConvertInputToValue(const Settings* settings,
 118                             const std::string& input,
 119                             const ParseNode* origin,
 120                             const Value& original_input_conversion,
 121                             const std::string& input_conversion,
 122                             Err* err) {
 123   if (input_conversion.empty())
 124     return Value();  // Empty string means discard the result.
 125
 126   const char kTrimPrefix[] = "trim ";
 127   if (StartsWithASCII(input_conversion, kTrimPrefix, true)) {
 128     std::string trimmed;
 129     base::TrimWhitespaceASCII(input, base::TRIM_ALL, &trimmed);
 130
 131     // Remove "trim" prefix from the input conversion and re-run.
 132     return DoConvertInputToValue(
 133         settings, trimmed, origin, original_input_conversion,
 134         input_conversion.substr(arraysize(kTrimPrefix) - 1), err);
 135   }
 136
 137   if (input_conversion == "value")
 138     return ParseValueOrScope(settings, input, PARSE_VALUE, origin, err);
 139   if (input_conversion == "string")
 140     return Value(origin, input);
 141   if (input_conversion == "list lines")
 142     return ParseList(input, origin, err);
 143   if (input_conversion == "scope")
 144     return ParseValueOrScope(settings, input, PARSE_SCOPE, origin, err);
 145
 146   *err = Err(original_input_conversion, "Not a valid input_conversion.",
 147              "Have you considered a career in retail?");
 148   return Value();
 149 }
 150
 151 }  // namespace
 152
 153 extern const char kInputConversion_Help[] =
 154     "input_conversion: Specifies how to transform input to a variable.\n"
 155     "\n"
 156     "  input_conversion is an argument to read_file and exec_script that\n"
 157     "  specifies how the result of the read operation should be converted\n"
 158     "  into a variable.\n"
 159     "\n"
 160     "  \"\" (the default)\n"
 161     "      Discard the result and return None.\n"
 162     "\n"
 163     "  \"list lines\"\n"
 164     "      Return the file contents as a list, with a string for each line.\n"
 165     "      The newlines will not be present in the result. The last line may\n"
 166     "      or may not end in a newline.\n"
 167     "\n"
 168     "      After splitting, each individual line will be trimmed of\n"
 169     "      whitespace on both ends.\n"
 170     "\n"
 171     "  \"scope\"\n"
 172     "      Execute the block as GN code and return a scope with the\n"
 173     "      resulting values in it. If the input was:\n"
 174     "        a = [ \"hello.cc\", \"world.cc\" ]\n"
 175     "        b = 26\n"
 176     "      and you read the result into a variable named \"val\", then you\n"
 177     "      could access contents the \".\" operator on \"val\":\n"
 178     "        sources = val.a\n"
 179     "        some_count = val.b\n"
 180     "\n"
 181     "  \"string\"\n"
 182     "      Return the file contents into a single string.\n"
 183     "\n"
 184     "  \"value\"\n"
 185     "      Parse the input as if it was a literal rvalue in a buildfile.\n"
 186     "      Examples of typical program output using this mode:\n"
 187     "        [ \"foo\", \"bar\" ]     (result will be a list)\n"
 188     "      or\n"
 189     "        \"foo bar\"            (result will be a string)\n"
 190     "      or\n"
 191     "        5                    (result will be an integer)\n"
 192     "\n"
 193     "      Note that if the input is empty, the result will be a null value\n"
 194     "      which will produce an error if assigned to a variable.\n"
 195     "\n"
 196     "  \"trim ...\"\n"
 197     "      Prefixing any of the other transformations with the word \"trim\"\n"
 198     "      will result in whitespace being trimmed from the beginning and end\n"
 199     "      of the result before processing.\n"
 200     "\n"
 201     "      Examples: \"trim string\" or \"trim list lines\"\n"
 202     "\n"
 203     "      Note that \"trim value\" is useless because the value parser skips\n"
 204     "      whitespace anyway.\n";
 205
 206 Value ConvertInputToValue(const Settings* settings,
 207                           const std::string& input,
 208                           const ParseNode* origin,
 209                           const Value& input_conversion_value,
 210                           Err* err) {
 211   if (input_conversion_value.type() == Value::NONE)
 212     return Value();  // Allow null inputs to mean discard the result.
 213   if (!input_conversion_value.VerifyTypeIs(Value::STRING, err))
 214     return Value();
 215   return DoConvertInputToValue(settings, input, origin, input_conversion_value,
 216                                input_conversion_value.string_value(), err);
 217 }