ExternalProject: Improve error when SOURCE_DIR is missing (#15560)

Mention the SOURCE_DIR that we checked and found empty or missing
so that the user can see the full path to what we expected to find.

Modules/ExternalProject.cmake

@@ -1866,7 +1866,18 @@ function(_ep_add_download_command name)
   else()
     _ep_is_dir_empty("${source_dir}" empty)
     if(${empty})
-      message(SEND_ERROR "error: no download info for '${name}' -- please specify existing/non-empty SOURCE_DIR or one of URL, CVS_REPOSITORY and CVS_MODULE, SVN_REPOSITORY, GIT_REPOSITORY, HG_REPOSITORY or DOWNLOAD_COMMAND")
+      message(SEND_ERROR
+        "No download info given for '${name}' and its source directory:\n"
+        " ${source_dir}\n"
+        "is not an existing non-empty directory.  Please specify one of:\n"
+        " * SOURCE_DIR with an existing non-empty directory\n"
+        " * URL\n"
+        " * GIT_REPOSITORY\n"
+        " * HG_REPOSITORY\n"
+        " * CVS_REPOSITORY and CVS_MODULE\n"
+        " * SVN_REVISION\n"
+        " * DOWNLOAD_COMMAND"
+        )
     endif()
   endif()
 

Tests/RunCMake/ExternalProject/NoOptions-result.txt

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

Tests/RunCMake/ExternalProject/NoOptions-stderr.txt

@@ -0,0 +1,18 @@
+^CMake Error at .*/Modules/ExternalProject.cmake:[0-9]+ \(message\):
+  No download info given for 'MyProj' and its source directory:
+
+   .*/Tests/RunCMake/ExternalProject/NoOptions-build/MyProj-prefix/src/MyProj
+
+  is not an existing non-empty directory.  Please specify one of:
+
+   \* SOURCE_DIR with an existing non-empty directory
+   \* URL
+   \* GIT_REPOSITORY
+   \* HG_REPOSITORY
+   \* CVS_REPOSITORY and CVS_MODULE
+   \* SVN_REVISION
+   \* DOWNLOAD_COMMAND
+Call Stack \(most recent call first\):
+  .*/Modules/ExternalProject.cmake:[0-9]+ \(_ep_add_download_command\)
+  NoOptions.cmake:[0-9]+ \(ExternalProject_Add\)
+  CMakeLists.txt:[0-9]+ \(include\)$

Tests/RunCMake/ExternalProject/NoOptions.cmake

@@ -0,0 +1,2 @@
+include(ExternalProject)
+ExternalProject_Add(MyProj)

Tests/RunCMake/ExternalProject/RunCMakeTest.cmake

@@ -1,5 +1,8 @@
 include(RunCMake)
 
+run_cmake(NoOptions)
+run_cmake(SourceEmpty)
+run_cmake(SourceMissing)
 run_cmake(CMAKE_CACHE_ARGS)
 run_cmake(CMAKE_CACHE_DEFAULT_ARGS)
 run_cmake(CMAKE_CACHE_mix)

Tests/RunCMake/ExternalProject/SourceEmpty-result.txt

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

Tests/RunCMake/ExternalProject/SourceEmpty-stderr.txt

@@ -0,0 +1,18 @@
+^CMake Error at .*/Modules/ExternalProject.cmake:[0-9]+ \(message\):
+  No download info given for 'MyProj' and its source directory:
+
+   .*/Tests/RunCMake/ExternalProject/SourceEmpty-build/SourceEmpty
+
+  is not an existing non-empty directory.  Please specify one of:
+
+   \* SOURCE_DIR with an existing non-empty directory
+   \* URL
+   \* GIT_REPOSITORY
+   \* HG_REPOSITORY
+   \* CVS_REPOSITORY and CVS_MODULE
+   \* SVN_REVISION
+   \* DOWNLOAD_COMMAND
+Call Stack \(most recent call first\):
+  .*/Modules/ExternalProject.cmake:[0-9]+ \(_ep_add_download_command\)
+  SourceEmpty.cmake:[0-9]+ \(ExternalProject_Add\)
+  CMakeLists.txt:[0-9]+ \(include\)$

Tests/RunCMake/ExternalProject/SourceEmpty.cmake

@@ -0,0 +1,5 @@
+include(ExternalProject)
+set(source_dir "${CMAKE_CURRENT_BINARY_DIR}/SourceEmpty")
+file(REMOVE_RECURSE "${source_dir}")
+file(MAKE_DIRECTORY "${source_dir}")
+ExternalProject_Add(MyProj SOURCE_DIR "${source_dir}")

Tests/RunCMake/ExternalProject/SourceMissing-result.txt

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

Tests/RunCMake/ExternalProject/SourceMissing-stderr.txt

@@ -0,0 +1,18 @@
+^CMake Error at .*/Modules/ExternalProject.cmake:[0-9]+ \(message\):
+  No download info given for 'MyProj' and its source directory:
+
+   .*/Tests/RunCMake/ExternalProject/SourceMissing-build/SourceMissing
+
+  is not an existing non-empty directory.  Please specify one of:
+
+   \* SOURCE_DIR with an existing non-empty directory
+   \* URL
+   \* GIT_REPOSITORY
+   \* HG_REPOSITORY
+   \* CVS_REPOSITORY and CVS_MODULE
+   \* SVN_REVISION
+   \* DOWNLOAD_COMMAND
+Call Stack \(most recent call first\):
+  .*/Modules/ExternalProject.cmake:[0-9]+ \(_ep_add_download_command\)
+  SourceMissing.cmake:[0-9]+ \(ExternalProject_Add\)
+  CMakeLists.txt:[0-9]+ \(include\)$

Tests/RunCMake/ExternalProject/SourceMissing.cmake

@@ -0,0 +1,2 @@
+include(ExternalProject)
+ExternalProject_Add(MyProj SOURCE_DIR SourceMissing)