Merge topic 'ExternalProject-declare-download-byproducts'

872daff159 ExternalProject: declare byproducts for the download step

Acked-by: Kitware Robot <[email protected]>
Merge-request: !8823

Help/release/dev/ExternalProject-declare-download-byproducts.rst

@@ -0,0 +1,8 @@
+ExternalProject-declare-download-byproducts
+-------------------------------------------
+
+* The :module:`ExternalProject` module now declares ``BYPRODUCTS`` for the
+  downloaded file for generated ``download`` steps. Previously, if multiple
+  external projects downloaded to the same file, hash verification could fail.
+  Now, when using the :ref:`Ninja Generators`, this scenario is detected and
+  Ninja will raise an error stating that multiple rules generate the same file.

Modules/ExternalProject.cmake

@@ -2825,6 +2825,7 @@ function(_ep_add_download_command name)
   set(comment)
   set(work_dir)
   set(extra_repo_info)
+  set(byproduct_file)
 
   if(cmd_set)
     set(work_dir ${download_dir})
@@ -3105,14 +3106,16 @@ hash=${hash}
           get_filename_component(fname "${fname}" NAME)
         else()
           # Fall back to a default file name.  The actual file name does not
-          # matter because it is used only internally and our extraction tool
-          # inspects the file content directly.  If it turns out the wrong URL
-          # was given that will be revealed during the build which is an easier
-          # place for users to diagnose than an error here anyway.
-          set(fname "archive.tar")
+          # matter as long as it doesn't conflict with other projects because
+          # it is used only internally and our extraction tool inspects the
+          # file content directly.  If it turns out the wrong URL was given
+          # that will be revealed during the build which is an easier place for
+          # users to diagnose than an error here anyway.
+          set(fname "${name}-archive.tar")
         endif()
         string(REPLACE ";" "-" fname "${fname}")
         set(file ${download_dir}/${fname})
+        set(byproduct_file "${download_dir}/${fname}")
         get_property(timeout TARGET ${name} PROPERTY _EP_TIMEOUT)
         get_property(inactivity_timeout
           TARGET ${name}
@@ -3289,6 +3292,7 @@ hash=${hash}
       COMMAND ${__cmdQuoted}
       WORKING_DIRECTORY \${work_dir}
       DEPENDS \${depends}
+      BYPRODUCTS \${byproduct_file}
       DEPENDEES mkdir
       ${log}
       ${uses_terminal}