cmake: Add internal -E mode to run include-what-you-use with the compiler

Add an internal "cmake -E __run_iwyu" mode to wrap the compiler call.
Run a given include-what-you-use command line with the compiler options
and report a warning if it finds anything.  Then run the real compiler.

Co-Author: Brad King <brad.king@kitware.com>

Source/cmcmd.cxx

@@ -211,6 +211,88 @@ int cmcmd::ExecuteCMakeCommand(std::vector<std::string>& args)
       return 0;
       }
 
+    // run include what you use command and then run the compile
+    // command. This is an internal undocumented option and should
+    // only be used by CMake itself when running iwyu.
+    else if (args[1] == "__run_iwyu")
+      {
+      if (args.size() < 3)
+        {
+        std::cerr << "__run_iwyu Usage: -E __run_iwyu [--iwyu=/path/iwyu]"
+          " -- compile command\n";
+        return 1;
+        }
+      bool doing_options = true;
+      std::vector<std::string> orig_cmd;
+      std::string iwyu;
+      for (std::string::size_type cc = 2; cc < args.size(); cc ++)
+        {
+        std::string const& arg = args[cc];
+        if (arg == "--")
+          {
+          doing_options = false;
+          }
+        else if (doing_options && cmHasLiteralPrefix(arg, "--iwyu="))
+          {
+          iwyu = arg.substr(7);
+          }
+        else if (doing_options)
+          {
+          std::cerr << "__run_iwyu given unknown argument: " << arg << "\n";
+          return 1;
+          }
+        else
+          {
+          orig_cmd.push_back(arg);
+          }
+        }
+      if (iwyu.empty())
+        {
+        std::cerr << "__run_iwyu missing --iwyu=\n";
+        return 1;
+        }
+      if (orig_cmd.empty())
+        {
+        std::cerr << "__run_iwyu missing compile command after --\n";
+        return 1;
+        }
+
+      // Construct the iwyu command line by taking what was given
+      // and adding all the arguments we give to the compiler.
+      std::vector<std::string> iwyu_cmd;
+      cmSystemTools::ExpandListArgument(iwyu, iwyu_cmd, true);
+      iwyu_cmd.insert(iwyu_cmd.end(), orig_cmd.begin()+1, orig_cmd.end());
+
+      // Run the iwyu command line.  Capture its stderr and hide its stdout.
+      int ret = 0;
+      std::string stdErr;
+      if(!cmSystemTools::RunSingleCommand(iwyu_cmd, 0, &stdErr, &ret,
+                                          0, cmSystemTools::OUTPUT_NONE))
+        {
+        std::cerr << "Error running '" << iwyu_cmd[0] << "': "
+                  << stdErr << "\n";
+        return 1;
+        }
+
+      // Warn if iwyu reported anything.
+      if(stdErr.find("should remove these lines:") != stdErr.npos
+         || stdErr.find("should add these lines:") != stdErr.npos)
+        {
+        std::cerr << "Warning: include-what-you-use reported diagnostics:\n"
+                  << stdErr << "\n";
+        }
+
+      // Now run the real compiler command and return its result value.
+      if(!cmSystemTools::RunSingleCommand(orig_cmd, 0, &stdErr, &ret, 0,
+                                          cmSystemTools::OUTPUT_PASSTHROUGH))
+        {
+        std::cerr << "Error running '" << orig_cmd[0] << "': "
+                  << stdErr << "\n";
+        return 1;
+        }
+      return ret;
+      }
+
     // Echo string
     else if (args[1] == "echo" )
       {

Tests/RunCMake/CommandLine/E___run_iwyu-bad-iwyu-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/CommandLine/E___run_iwyu-bad-iwyu-stderr.txt

@@ -0,0 +1,2 @@
+^Error running 'iwyu-does-not-exist': [^
+]+$

Tests/RunCMake/CommandLine/E___run_iwyu-no----result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/CommandLine/E___run_iwyu-no----stderr.txt

@@ -0,0 +1 @@
+^__run_iwyu given unknown argument: command-does-not-exist$

Tests/RunCMake/CommandLine/E___run_iwyu-no-cc-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/CommandLine/E___run_iwyu-no-cc-stderr.txt

@@ -0,0 +1 @@
+^__run_iwyu missing compile command after --$

Tests/RunCMake/CommandLine/E___run_iwyu-no-iwyu-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/CommandLine/E___run_iwyu-no-iwyu-stderr.txt

@@ -0,0 +1 @@
+^__run_iwyu missing --iwyu=$

Tests/RunCMake/CommandLine/RunCMakeTest.cmake

@@ -12,6 +12,11 @@ run_cmake_command(E_echo_append ${CMAKE_COMMAND} -E echo_append)
 run_cmake_command(E_rename-no-arg ${CMAKE_COMMAND} -E rename)
 run_cmake_command(E_touch_nocreate-no-arg ${CMAKE_COMMAND} -E touch_nocreate)
 
+run_cmake_command(E___run_iwyu-no-iwyu ${CMAKE_COMMAND} -E __run_iwyu -- command-does-not-exist)
+run_cmake_command(E___run_iwyu-bad-iwyu ${CMAKE_COMMAND} -E __run_iwyu --iwyu=iwyu-does-not-exist -- command-does-not-exist)
+run_cmake_command(E___run_iwyu-no--- ${CMAKE_COMMAND} -E __run_iwyu --iwyu=iwyu-does-not-exist command-does-not-exist)
+run_cmake_command(E___run_iwyu-no-cc ${CMAKE_COMMAND} -E __run_iwyu --iwyu=iwyu-does-not-exist --)
+
 run_cmake_command(G_no-arg ${CMAKE_COMMAND} -G)
 run_cmake_command(G_bad-arg ${CMAKE_COMMAND} -G NoSuchGenerator)
 run_cmake_command(P_no-arg ${CMAKE_COMMAND} -P)