Eliminate clang man page generation warning for missing .rst files

[t-tye]

Summary

Update clang/docs/CMakeLists.txt for Sphinx man builder to do the same as for
the html builder to ensure .td generated .rst files are available to prevent
warnings of missing .rst files.

Document SOURCE_DIR named argument to add_sphinx_target function.

[scott.linder]

LGTM, I see no reason why this shouldn't apply for all generators.

clang/docs/CMakeLists.txt

function (gen_rst_file_from_td output_file td_option source docs_target)
   list(APPEND LLVM_TABLEGEN_FLAGS "-I${TABLEGEN_INCLUDE_DIR}")
   clang_tablegen(${output_file} ${td_option} SOURCE ${source} TARGET "gen-${output_file}")
   add_dependencies(${docs_target} "gen-${output_file}")
 endfunction()
 
 if (LLVM_ENABLE_SPHINX)
   include(AddSphinxTarget)
   if (SPHINX_FOUND)
-    if (${SPHINX_OUTPUT_HTML})
-      add_sphinx_target(html clang SOURCE_DIR "${CMAKE_CURRENT_BINARY_DIR}")
 
-      # Copy rst files to build directory before generating the html
-      # documentation.  Some of the rst files are generated, so they
-      # only exist in the build directory.  Sphinx needs all files in
-      # the same directory in order to generate the html, so we need to
-      # copy all the non-gnerated rst files from the source to the build
-      # directory before we run sphinx.
-      add_custom_target(copy-clang-rst-docs
-        COMMAND "${CMAKE_COMMAND}" -E copy_directory
-        "${CMAKE_CURRENT_SOURCE_DIR}"
-        "${CMAKE_CURRENT_BINARY_DIR}")
+    # Copy rst files to build directory before generating the
+    # the same directory in order to generate the files, so we need to
+    # copy all the non-generated rst files from the source to the build
+    # directory before we run Sphinx.
+
+    # Generated files
+    gen_rst_file_from_td(AttributeReference.rst -gen-attr-docs ../include/clang/Basic/Attr.td copy-clang-rst-docs)
+    gen_rst_file_from_td(DiagnosticsReference.rst -gen-diag-docs ../include/clang/Basic/Diagnostic.td copy-clang-rst-docs)
+    gen_rst_file_from_td(ClangCommandLineReference.rst -gen-opt-docs ../include/clang/Driver/ClangOptionDocs.td copy-clang-rst-docs)
+
+    if (${SPHINX_OUTPUT_HTML})
+      add_sphinx_target(html clang SOURCE_DIR "${CMAKE_CURRENT_BINARY_DIR}")
+
       add_dependencies(docs-clang-html copy-clang-rst-docs)
 
       add_custom_command(TARGET docs-clang-html POST_BUILD
         COMMAND "${CMAKE_COMMAND}" -E copy
         "${CMAKE_CURRENT_SOURCE_DIR}/LibASTMatchersReference.html"
         "${CMAKE_CURRENT_BINARY_DIR}/html/LibASTMatchersReference.html")
 
-      # Generated files
-      gen_rst_file_from_td(AttributeReference.rst -gen-attr-docs ../include/clang/Basic/Attr.td docs-clang-html)
-      gen_rst_file_from_td(DiagnosticsReference.rst -gen-diag-docs ../include/clang/Basic/Diagnostic.td docs-clang-html)
-      gen_rst_file_from_td(ClangCommandLineReference.rst -gen-opt-docs ../include/clang/Driver/ClangOptionDocs.td docs-clang-html)
     endif()
+
     if (${SPHINX_OUTPUT_MAN})
-      add_sphinx_target(man clang)
+      add_sphinx_target(man clang SOURCE_DIR "${CMAKE_CURRENT_BINARY_DIR}")
+      add_dependencies(docs-clang-man copy-clang-rst-docs)
     endif()
+
   endif()
 endif()

llvm/cmake/modules/AddSphinxTarget.cmake

 # Handy function for creating the different Sphinx targets.
 #
 # ``builder`` should be one of the supported builders used by
 # the sphinx-build command.
 #
 # ``project`` should be the project name
 #
 # Named arguments:
+# ``SOURCE_DIR`` source directory for Sphinx files. Defaults to
+#                ${CMAKE_CURRENT_SOURCE_DIR}.
+#
 # ``ENV_VARS`` should be a list of environment variables that should be set when
 #              running Sphinx. Each environment variable should be a string with
 #              the form KEY=VALUE.
 function (add_sphinx_target builder project)
   cmake_parse_arguments(ARG "" "SOURCE_DIR" "ENV_VARS" ${ARGN})
   set(SPHINX_BUILD_DIR "${CMAKE_CURRENT_BINARY_DIR}/${builder}")
   set(SPHINX_DOC_TREE_DIR "${CMAKE_CURRENT_BINARY_DIR}/_doctrees-${project}-${builder}")
   set(SPHINX_TARGET_NAME docs-${project}-${builder})