project: Add optional LANGUAGES keyword

Teach the project() command to recognize an optional "LANGUAGES"
keyword after the project name and prior to the list of languages.
Do not allow multiple copies of the keyword.  If the keyword is
specified and no languages are listed, imply NONE.

14 files changed, 53 insertions, 5 deletions

diff --git a/Help/command/project.rst b/Help/command/project.rst
index cb7d3fc..aabab65 100644
--- a/Help/command/project.rst
+++ b/Help/command/project.rst
@@ -5,7 +5,7 @@ Set a name and enable languages for the entire project.
 
 .. code-block:: cmake
 
- project(<PROJECT-NAME> [<language-name>...])
+ project(<PROJECT-NAME> [LANGUAGES] [<language-name>...])
 
 Sets the name of the project and stores the name in the
 :variable:`PROJECT_NAME` variable.  Additionally this sets variables
@@ -18,7 +18,8 @@ Sets the name of the project and stores the name in the
 Optionally you can specify which languages your project supports.
 Example languages are ``C``, ``CXX`` (i.e.  C++), ``Fortran``, etc.
 By default ``C`` and ``CXX`` are enabled if no language options are
-given.  Specify language ``NONE`` to skip enabling any languages.
+given.  Specify language ``NONE``, or use the ``LANGUAGES`` keyword
+and list no languages, to skip enabling any languages.
 
 If a variable exists called :variable:`CMAKE_PROJECT_<PROJECT-NAME>_INCLUDE`,
 the file pointed to by that variable will be included as the last step of the
diff --git a/Source/cmProjectCommand.cxx b/Source/cmProjectCommand.cxx
index 11f9a76..1dcb72b 100644
--- a/Source/cmProjectCommand.cxx
+++ b/Source/cmProjectCommand.cxx
@@ -62,15 +62,33 @@ bool cmProjectCommand
        "Value Computed by CMake", cmCacheManager::STATIC);
     }
 
+  bool haveLanguages = false;
   std::vector<std::string> languages;
-  if(args.size() > 1)
+  for(size_t i = 1; i < args.size(); ++i)
     {
-    for(size_t i =1; i < args.size(); ++i)
+    if(args[i] == "LANGUAGES")
+      {
+      if(haveLanguages)
+        {
+        this->Makefile->IssueMessage
+          (cmake::FATAL_ERROR, "LANGUAGES may be specified at most once.");
+        cmSystemTools::SetFatalErrorOccured();
+        return true;
+        }
+      haveLanguages = true;
+      }
+    else
       {
       languages.push_back(args[i]);
       }
     }
-  else
+
+  if (haveLanguages && languages.empty())
+    {
+    languages.push_back("NONE");
+    }
+
+  if (languages.empty())
     {
     // if no language is specified do c and c++
     languages.push_back("C");
diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index 9646e67..c29b736 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -82,6 +82,7 @@ add_RunCMake_test(include)
 add_RunCMake_test(include_directories)
 add_RunCMake_test(list)
 add_RunCMake_test(message)
+add_RunCMake_test(project)
 add_RunCMake_test(string)
 add_RunCMake_test(try_compile)
 add_RunCMake_test(set)
diff --git a/Tests/RunCMake/project/CMakeLists.txt b/Tests/RunCMake/project/CMakeLists.txt
new file mode 100644
index 0000000..12cd3c7
--- /dev/null
+++ b/Tests/RunCMake/project/CMakeLists.txt
@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 2.8.4)
+project(${RunCMake_TEST} NONE)
+include(${RunCMake_TEST}.cmake)
diff --git a/Tests/RunCMake/project/LanguagesEmpty-stdout.txt b/Tests/RunCMake/project/LanguagesEmpty-stdout.txt
new file mode 100644
index 0000000..fb9c7e8
--- /dev/null
+++ b/Tests/RunCMake/project/LanguagesEmpty-stdout.txt
@@ -0,0 +1 @@
+ENABLED_LANGUAGES='NONE'
diff --git a/Tests/RunCMake/project/LanguagesEmpty.cmake b/Tests/RunCMake/project/LanguagesEmpty.cmake
new file mode 100644
index 0000000..4de2cca
--- /dev/null
+++ b/Tests/RunCMake/project/LanguagesEmpty.cmake
@@ -0,0 +1,3 @@
+project(ProjectA LANGUAGES)
+get_property(langs GLOBAL PROPERTY ENABLED_LANGUAGES)
+message(STATUS "ENABLED_LANGUAGES='${langs}'")
diff --git a/Tests/RunCMake/project/LanguagesImplicit-stdout.txt b/Tests/RunCMake/project/LanguagesImplicit-stdout.txt
new file mode 100644
index 0000000..fb9c7e8
--- /dev/null
+++ b/Tests/RunCMake/project/LanguagesImplicit-stdout.txt
@@ -0,0 +1 @@
+ENABLED_LANGUAGES='NONE'
diff --git a/Tests/RunCMake/project/LanguagesImplicit.cmake b/Tests/RunCMake/project/LanguagesImplicit.cmake
new file mode 100644
index 0000000..e408454
--- /dev/null
+++ b/Tests/RunCMake/project/LanguagesImplicit.cmake
@@ -0,0 +1,3 @@
+project(ProjectA NONE)
+get_property(langs GLOBAL PROPERTY ENABLED_LANGUAGES)
+message(STATUS "ENABLED_LANGUAGES='${langs}'")
diff --git a/Tests/RunCMake/project/LanguagesNONE-stdout.txt b/Tests/RunCMake/project/LanguagesNONE-stdout.txt
new file mode 100644
index 0000000..fb9c7e8
--- /dev/null
+++ b/Tests/RunCMake/project/LanguagesNONE-stdout.txt
@@ -0,0 +1 @@
+ENABLED_LANGUAGES='NONE'
diff --git a/Tests/RunCMake/project/LanguagesNONE.cmake b/Tests/RunCMake/project/LanguagesNONE.cmake
new file mode 100644
index 0000000..2c0125f
--- /dev/null
+++ b/Tests/RunCMake/project/LanguagesNONE.cmake
@@ -0,0 +1,3 @@
+project(ProjectA LANGUAGES NONE)
+get_property(langs GLOBAL PROPERTY ENABLED_LANGUAGES)
+message(STATUS "ENABLED_LANGUAGES='${langs}'")
diff --git a/Tests/RunCMake/project/LanguagesTwice-result.txt b/Tests/RunCMake/project/LanguagesTwice-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/project/LanguagesTwice-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/project/LanguagesTwice-stderr.txt b/Tests/RunCMake/project/LanguagesTwice-stderr.txt
new file mode 100644
index 0000000..9c69dd0
--- /dev/null
+++ b/Tests/RunCMake/project/LanguagesTwice-stderr.txt
@@ -0,0 +1,4 @@
+CMake Error at LanguagesTwice.cmake:1 \(project\):
+  LANGUAGES may be specified at most once.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)$
diff --git a/Tests/RunCMake/project/LanguagesTwice.cmake b/Tests/RunCMake/project/LanguagesTwice.cmake
new file mode 100644
index 0000000..6c4a3dc
--- /dev/null
+++ b/Tests/RunCMake/project/LanguagesTwice.cmake
@@ -0,0 +1,2 @@
+project(ProjectA LANGUAGES NONE LANGUAGES)
+message("This line not reached.")
diff --git a/Tests/RunCMake/project/RunCMakeTest.cmake b/Tests/RunCMake/project/RunCMakeTest.cmake
new file mode 100644
index 0000000..cac0f46
--- /dev/null
+++ b/Tests/RunCMake/project/RunCMakeTest.cmake
@@ -0,0 +1,6 @@
+include(RunCMake)
+
+run_cmake(LanguagesImplicit)
+run_cmake(LanguagesEmpty)
+run_cmake(LanguagesNONE)
+run_cmake(LanguagesTwice)