find_*: Add support for REQUIRED keyword

In the same spirit as the REQUIRED keyword on find_package, this will
stop cmake execution with an error on a failed find_program, find_file,
find_path or find_library.

Help/command/FIND_XXX.txt

@@ -15,6 +15,7 @@ The general signature is:
              [PATHS path1 [path2 ... ENV var]]
              [PATH_SUFFIXES suffix1 [suffix2 ...]]
              [DOC "cache documentation string"]
+             [REQUIRED]
              [NO_DEFAULT_PATH]
              [NO_PACKAGE_ROOT_PATH]
              [NO_CMAKE_PATH]
@@ -31,8 +32,9 @@ A cache entry named by ``<VAR>`` is created to store the result
 of this command.
 If the |SEARCH_XXX| is found the result is stored in the variable
 and the search will not be repeated unless the variable is cleared.
-If nothing is found, the result will be
-``<VAR>-NOTFOUND``, and the search will be attempted again the
+If nothing is found, the result will be ``<VAR>-NOTFOUND``.
+The ``REQUIRED`` option stops processing with an error message if nothing
+is found, otherwise the search will be attempted again the
 next time |FIND_XXX| is invoked with the same variable.
 
 Options include:
@@ -57,6 +59,9 @@ Options include:
 ``DOC``
   Specify the documentation string for the ``<VAR>`` cache entry.
 
+``REQUIRED``
+  Stop processing with an error message if nothing is found.
+
 If ``NO_DEFAULT_PATH`` is specified, then no additional paths are
 added to the search.
 If ``NO_DEFAULT_PATH`` is not specified, the search process is as follows:

Help/release/dev/required_find_commands.rst

@@ -0,0 +1,6 @@
+required_find_commands
+----------------------
+
+* The :command:`find_program`, :command:`find_library`, :command:`find_path`
+  and :command:`find_file` commands gained a new ``REQUIRED`` option that will
+  stop processing with an error message if nothing is found.

Source/cmFindBase.cxx

@@ -111,6 +111,10 @@ bool cmFindBase::ParseArguments(std::vector<std::string> const& argsIn)
     } else if (args[j] == "NO_SYSTEM_PATH") {
       doing = DoingNone;
       this->NoDefaultPath = true;
+    } else if (args[j] == "REQUIRED") {
+      doing = DoingNone;
+      this->Required = true;
+      newStyle = true;
     } else if (this->CheckCommonArgument(args[j])) {
       doing = DoingNone;
     } else {

Source/cmFindBase.h

@@ -53,6 +53,8 @@ protected:
   bool AlreadyInCache = false;
   bool AlreadyInCacheWithoutMetaInfo = false;
 
+  bool Required = false;
+
 private:
   // Add pieces of the search.
   void FillPackageRootPath();

Source/cmFindLibraryCommand.cxx

@@ -12,6 +12,7 @@
 
 #include "cmGlobalGenerator.h"
 #include "cmMakefile.h"
+#include "cmMessageType.h"
 #include "cmState.h"
 #include "cmStateTypes.h"
 #include "cmStringAlgorithms.h"
@@ -84,6 +85,13 @@ bool cmFindLibraryCommand::InitialPass(std::vector<std::string> const& argsIn)
   this->Makefile->AddCacheDefinition(this->VariableName, notfound.c_str(),
                                      this->VariableDocumentation.c_str(),
                                      cmStateEnums::FILEPATH);
+  if (this->Required) {
+    this->Makefile->IssueMessage(
+      MessageType::FATAL_ERROR,
+      "Could not find " + this->VariableName +
+        " using the following names: " + cmJoin(this->Names, ", "));
+    cmSystemTools::SetFatalErrorOccured();
+  }
   return true;
 }
 

Source/cmFindPathCommand.cxx

@@ -5,6 +5,7 @@
 #include "cmsys/Glob.hxx"
 
 #include "cmMakefile.h"
+#include "cmMessageType.h"
 #include "cmStateTypes.h"
 #include "cmStringAlgorithms.h"
 #include "cmSystemTools.h"
@@ -51,6 +52,13 @@ bool cmFindPathCommand::InitialPass(std::vector<std::string> const& argsIn)
     this->VariableName, (this->VariableName + "-NOTFOUND").c_str(),
     this->VariableDocumentation.c_str(),
     (this->IncludeFileInPath) ? cmStateEnums::FILEPATH : cmStateEnums::PATH);
+  if (this->Required) {
+    this->Makefile->IssueMessage(
+      MessageType::FATAL_ERROR,
+      "Could not find " + this->VariableName +
+        " using the following files: " + cmJoin(this->Names, ", "));
+    cmSystemTools::SetFatalErrorOccured();
+  }
   return true;
 }
 

Source/cmFindProgramCommand.cxx

@@ -3,6 +3,7 @@
 #include "cmFindProgramCommand.h"
 
 #include "cmMakefile.h"
+#include "cmMessageType.h"
 #include "cmStateTypes.h"
 #include "cmStringAlgorithms.h"
 #include "cmSystemTools.h"
@@ -136,6 +137,13 @@ bool cmFindProgramCommand::InitialPass(std::vector<std::string> const& argsIn)
   this->Makefile->AddCacheDefinition(
     this->VariableName, (this->VariableName + "-NOTFOUND").c_str(),
     this->VariableDocumentation.c_str(), cmStateEnums::FILEPATH);
+  if (this->Required) {
+    this->Makefile->IssueMessage(
+      MessageType::FATAL_ERROR,
+      "Could not find " + this->VariableName +
+        " using the following names: " + cmJoin(this->Names, ", "));
+    cmSystemTools::SetFatalErrorOccured();
+  }
   return true;
 }
 

Tests/RunCMake/find_file/Required-result.txt

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

Tests/RunCMake/find_file/Required-stderr.txt

@@ -0,0 +1,4 @@
+CMake Error at Required.cmake:9 \(find_file\):
+  Could not find FILE_doNotExists using the following files: doNotExists.h
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)

Tests/RunCMake/find_file/Required-stdout.txt

@@ -0,0 +1 @@
+-- FILE_exists='[^']*/Tests/RunCMake/find_file/include/PrefixInPATH.h'

Tests/RunCMake/find_file/Required.cmake

@@ -0,0 +1,12 @@
+find_file(FILE_exists
+  NAMES PrefixInPATH.h
+  PATHS ${CMAKE_CURRENT_SOURCE_DIR}/include
+  NO_DEFAULT_PATH
+  REQUIRED
+  )
+message(STATUS "FILE_exists='${FILE_exists}'")
+
+find_file(FILE_doNotExists
+  NAMES doNotExists.h
+  REQUIRED
+  )

Tests/RunCMake/find_file/RunCMakeTest.cmake

@@ -3,3 +3,4 @@ include(RunCMake)
 run_cmake(FromPATHEnv)
 run_cmake(FromPrefixPath)
 run_cmake(PrefixInPATH)
+run_cmake(Required)

Tests/RunCMake/find_library/Required-result.txt

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

Tests/RunCMake/find_library/Required-stderr.txt

@@ -0,0 +1,4 @@
+CMake Error at Required.cmake:11 \(find_library\):
+  Could not find LIB_doNotExists using the following names: doNotExists
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)

Tests/RunCMake/find_library/Required-stdout.txt

@@ -0,0 +1 @@
+-- LIB_exists='[^']*/Tests/RunCMake/find_library/lib/libPrefixInPATH.a'

Tests/RunCMake/find_library/Required.cmake

@@ -0,0 +1,14 @@
+list(APPEND CMAKE_FIND_LIBRARY_PREFIXES lib)
+list(APPEND CMAKE_FIND_LIBRARY_SUFFIXES .a)
+find_library(LIB_exists
+  NAMES PrefixInPATH
+  PATHS ${CMAKE_CURRENT_SOURCE_DIR}/lib
+  NO_DEFAULT_PATH
+  REQUIRED
+  )
+message(STATUS "LIB_exists='${LIB_exists}'")
+
+find_library(LIB_doNotExists
+  NAMES doNotExists
+  REQUIRED
+  )

Tests/RunCMake/find_library/RunCMakeTest.cmake

@@ -7,3 +7,4 @@ if(CMAKE_HOST_UNIX)
   run_cmake(LibArchLink)
 endif()
 run_cmake(PrefixInPATH)
+run_cmake(Required)

Tests/RunCMake/find_path/Required-result.txt

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

Tests/RunCMake/find_path/Required-stderr.txt

@@ -0,0 +1,4 @@
+CMake Error at Required.cmake:9 \(find_path\):
+  Could not find PATH_doNotExists using the following files: doNotExists.h
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)

Tests/RunCMake/find_path/Required-stdout.txt

@@ -0,0 +1 @@
+-- PATH_exists='[^']*/Tests/RunCMake/find_path/include'

Tests/RunCMake/find_path/Required.cmake

@@ -0,0 +1,12 @@
+find_path(PATH_exists
+  NAMES PrefixInPATH.h
+  PATHS ${CMAKE_CURRENT_SOURCE_DIR}/include
+  NO_DEFAULT_PATH
+  REQUIRED
+  )
+message(STATUS "PATH_exists='${PATH_exists}'")
+
+find_path(PATH_doNotExists
+  NAMES doNotExists.h
+  REQUIRED
+  )

Tests/RunCMake/find_path/RunCMakeTest.cmake

@@ -3,6 +3,7 @@ include(RunCMake)
 run_cmake(EmptyOldStyle)
 run_cmake(FromPATHEnv)
 run_cmake(PrefixInPATH)
+run_cmake(Required)
 
 if(APPLE)
   run_cmake(FrameworksWithSubdirs)

Tests/RunCMake/find_program/Required-result.txt

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

Tests/RunCMake/find_program/Required-stderr.txt

@@ -0,0 +1,4 @@
+CMake Error at Required.cmake:9 \(find_program\):
+  Could not find PROG_AandB using the following names: testAandB
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)

Tests/RunCMake/find_program/Required-stdout.txt

@@ -0,0 +1 @@
+-- PROG_A='[^']*/Tests/RunCMake/find_program/A/testA'

Tests/RunCMake/find_program/Required.cmake

@@ -0,0 +1,12 @@
+find_program(PROG_A
+  NAMES testA
+  PATHS ${CMAKE_CURRENT_SOURCE_DIR}/A
+  NO_DEFAULT_PATH
+  REQUIRED
+  )
+message(STATUS "PROG_A='${PROG_A}'")
+
+find_program(PROG_AandB
+  NAMES testAandB
+  REQUIRED
+  )

Tests/RunCMake/find_program/RunCMakeTest.cmake

@@ -4,6 +4,7 @@ run_cmake(EnvAndHints)
 run_cmake(DirsPerName)
 run_cmake(NamesPerDir)
 run_cmake(RelAndAbsPath)
+run_cmake(Required)
 
 if(CMAKE_SYSTEM_NAME MATCHES "^(Windows|CYGWIN)$")
   run_cmake(WindowsCom)