add an include statement

manual.asciidoc

@@ -224,7 +224,9 @@ A file is a series of declarations.  A declaration can be one of:
 
 3. Variable declarations, which look like +_variable_ = _value_+.
 
-4. References to more files, which look like +subninja _path_+.
+4. References to more files, which look like +subninja _path_+ or
+   +include _path_+.  The difference between these is explained below
+   <<ref_scope,in the discussion about scoping>>.
 
 Comments begin with `#` and extend to the end of the line.
 
@@ -299,11 +301,18 @@ introduces a new scope.  The included `subninja` file may use the
 variables from the parent file, and shadow their values for the file's
 scope, but it won't affect values of the variables in the parent.
 
+To include another `.ninja` file in the current scope, much like a C
+`#include` statement, use `include` instead of `subninja`.
+
 Variable declarations indented in a `build` block are scoped to the
 `build` block.  This scope is inherited by the `rule`.  The full
 lookup order for a variable referenced in a rule is:
 
 1. Rule-level variables (i.e. `$in`, `$command`).
+
 2. Build-level variables from the `build` that references this rule.
-3. File-level variables from the current file.
-4. File-level variables from any file that included this file.
+
+3. File-level variables from the file that the `build` line was in.
+
+4. Variables from the file that included that file using the
+   `subninja` keyword.

src/parsers.cc

@@ -15,18 +15,18 @@ string Token::AsString() const {
   case RULE:     return "'rule'";
   case BUILD:    return "'build'";
   case SUBNINJA: return "'subninja'";
+  case INCLUDE:  return "'include'";
   case NEWLINE:  return "newline";
   case EQUALS:   return "'='";
   case COLON:    return "':'";
   case PIPE:     return "'|'";
   case TEOF:     return "eof";
   case INDENT:   return "indenting in";
   case OUTDENT:  return "indenting out";
-  case NONE:
-  default:
-    assert(false);
-    return "";
+  case NONE:     break;
   }
+  assert(false);
+  return "";
 }
 
 void Tokenizer::Start(const char* start, const char* end) {
@@ -168,6 +168,8 @@ Token::Type Tokenizer::PeekToken() {
       token_.type_ = Token::RULE;
     else if (len == 5 && memcmp(token_.pos_, "build", 5) == 0)
       token_.type_ = Token::BUILD;
+    else if (len == 7 && memcmp(token_.pos_, "include", 7) == 0)
+      token_.type_ = Token::INCLUDE;
     else if (len == 8 && memcmp(token_.pos_, "subninja", 8) == 0)
       token_.type_ = Token::SUBNINJA;
     else
@@ -250,7 +252,8 @@ bool ManifestParser::Parse(const string& input, string* err) {
           return false;
         break;
       case Token::SUBNINJA:
-        if (!ParseSubNinja(err))
+      case Token::INCLUDE:
+        if (!ParseFileInclude(tokenizer_.PeekToken(), err))
           return false;
         break;
       case Token::IDENT: {
@@ -469,12 +472,12 @@ bool ManifestParser::ParseEdge(string* err) {
   return true;
 }
 
-bool ManifestParser::ParseSubNinja(string* err) {
-  if (!tokenizer_.ExpectToken(Token::SUBNINJA, err))
+bool ManifestParser::ParseFileInclude(Token::Type type, string* err) {
+  if (!tokenizer_.ExpectToken(type, err))
     return false;
   string path;
   if (!tokenizer_.ReadIdent(&path))
-    return tokenizer_.Error("expected subninja path", err);
+    return tokenizer_.Error("expected path to ninja file", err);
   if (!tokenizer_.Newline(err))
     return false;
 
@@ -483,8 +486,15 @@ bool ManifestParser::ParseSubNinja(string* err) {
     return false;
 
   ManifestParser subparser(state_, file_reader_);
-  subparser.env_ = new BindingEnv;
-  subparser.env_->parent_ = env_;
+  if (type == Token::SUBNINJA) {
+    // subninja: Construct a new scope for the new parser.
+    subparser.env_ = new BindingEnv;
+    subparser.env_->parent_ = env_;
+  } else {
+    // include: Reuse the current scope.
+    subparser.env_ = env_;
+  }
+
   string sub_err;
   if (!subparser.Parse(contents, &sub_err))
     return tokenizer_.Error("in '" + path + "': " + sub_err, err);

src/parsers.h

@@ -16,6 +16,7 @@ struct Token {
     RULE,
     BUILD,
     SUBNINJA,
+    INCLUDE,
     NEWLINE,
     EQUALS,
     COLON,
@@ -87,7 +88,9 @@ struct ManifestParser {
   // within the value immediately.
   bool ParseLet(string* key, string* val, bool expand, string* err);
   bool ParseEdge(string* err);
-  bool ParseSubNinja(string* err);
+
+  // Parse either a 'subninja' or 'include' line.
+  bool ParseFileInclude(Token::Type type, string* err);
 
   State* state_;
   BindingEnv* env_;

src/parsers_test.cc

@@ -278,6 +278,17 @@ TEST_F(ParserTest, SubNinja) {
   EXPECT_EQ("varref outer", state.edges_[2]->EvaluateCommand());
 }
 
+TEST_F(ParserTest, Include) {
+  files_["include.ninja"] = "var = inner\n";
+  ASSERT_NO_FATAL_FAILURE(AssertParse(
+"var = outer\n"
+"include include.ninja\n"));
+
+  ASSERT_EQ(1, files_read_.size());
+  EXPECT_EQ("include.ninja", files_read_[0]);
+  EXPECT_EQ("inner", state.bindings_.LookupVariable("var"));
+}
+
 TEST_F(ParserTest, OrderOnly) {
   ASSERT_NO_FATAL_FAILURE(AssertParse(
 "rule cat\n  command = cat $in > $out\n"