From 353da6cce4228f0520585dc12b9b77ed7032d59d Mon Sep 17 00:00:00 2001
From: jhendersonHDF <jhenderson@hdfgroup.org>
Date: Wed, 18 Mar 2026 12:35:43 -0500
Subject: [PATCH] Fix some filters testing issues (#6299)

---
 .github/workflows/cygwin.yml          |  1 +
 .github/workflows/macos-26-matrix.yml |  1 +
 .github/workflows/par-source.yml      |  2 ++
 .github/workflows/script.yml          |  7 +++++++
 CMakePlugins.cmake                    | 12 ++++++++++--
 CMakePresets.json                     |  4 +++-
 6 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/cygwin.yml b/.github/workflows/cygwin.yml
index db371c70cef..e0f8170af8b 100644
--- a/.github/workflows/cygwin.yml
+++ b/.github/workflows/cygwin.yml
@@ -103,6 +103,7 @@ jobs:
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_ZLIB_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_SZIP_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_PLUGIN_SUPPORT:BOOL=ON")
+            set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_EXTERNAL:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DLIBAEC_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DZLIB_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_LOCALCONTENT:BOOL=OFF")
diff --git a/.github/workflows/macos-26-matrix.yml b/.github/workflows/macos-26-matrix.yml
index 6c60558c83e..033ed088643 100644
--- a/.github/workflows/macos-26-matrix.yml
+++ b/.github/workflows/macos-26-matrix.yml
@@ -218,6 +218,7 @@ jobs:
         if [[ "${{ matrix.plugins }}" == "ON" ]]; then
           CMAKE_OPTS="$CMAKE_OPTS -DHDF5_ENABLE_PLUGIN_SUPPORT=ON"
           CMAKE_OPTS="$CMAKE_OPTS -DHDF5_ALLOW_EXTERNAL_SUPPORT=TGZ"
+          CMAKE_OPTS="$CMAKE_OPTS -DPLUGIN_USE_EXTERNAL=ON"
           CMAKE_OPTS="$CMAKE_OPTS -DPLUGIN_USE_LOCALCONTENT=OFF"
         fi
 
diff --git a/.github/workflows/par-source.yml b/.github/workflows/par-source.yml
index ae2f93a0d58..d4ee8c7b7f9 100644
--- a/.github/workflows/par-source.yml
+++ b/.github/workflows/par-source.yml
@@ -146,6 +146,7 @@ jobs:
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_ZLIB_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_SZIP_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_PLUGIN_SUPPORT:BOOL=ON")
+            set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_EXTERNAL:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DLIBAEC_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DZLIB_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_LOCALCONTENT:BOOL=OFF")
@@ -262,6 +263,7 @@ jobs:
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_ZLIB_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_SZIP_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_PLUGIN_SUPPORT:BOOL=ON")
+            set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_EXTERNAL:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DLIBAEC_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DZLIB_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_LOCALCONTENT:BOOL=OFF")
diff --git a/.github/workflows/script.yml b/.github/workflows/script.yml
index 4e39ef3f024..a2caed95240 100644
--- a/.github/workflows/script.yml
+++ b/.github/workflows/script.yml
@@ -124,6 +124,7 @@ jobs:
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_ZLIB_SUPPORT:BOOL=ON")
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_SZIP_SUPPORT:BOOL=ON")
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_PLUGIN_SUPPORT:BOOL=ON")
+              set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_EXTERNAL:BOOL=ON")
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DLIBAEC_USE_LOCALCONTENT:BOOL=OFF")
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DZLIB_USE_LOCALCONTENT:BOOL=OFF")
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_LOCALCONTENT:BOOL=OFF")
@@ -221,6 +222,7 @@ jobs:
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_ZLIB_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_SZIP_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_PLUGIN_SUPPORT:BOOL=ON")
+            set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_EXTERNAL:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DLIBAEC_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DZLIB_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_LOCALCONTENT:BOOL=OFF")
@@ -342,6 +344,7 @@ jobs:
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_ZLIB_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_SZIP_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_PLUGIN_SUPPORT:BOOL=ON")
+            set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_EXTERNAL:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DLIBAEC_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DZLIB_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_LOCALCONTENT:BOOL=OFF")
@@ -459,6 +462,7 @@ jobs:
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_ZLIB_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_SZIP_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_PLUGIN_SUPPORT:BOOL=ON")
+            set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_EXTERNAL:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DLIBAEC_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DZLIB_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_LOCALCONTENT:BOOL=OFF")
@@ -573,6 +577,7 @@ jobs:
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_ZLIB_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_SZIP_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_PLUGIN_SUPPORT:BOOL=ON")
+            set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_EXTERNAL:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DLIBAEC_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DZLIB_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_LOCALCONTENT:BOOL=OFF")
@@ -680,6 +685,7 @@ jobs:
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_ZLIB_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_SZIP_SUPPORT:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_PLUGIN_SUPPORT:BOOL=ON")
+            set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_EXTERNAL:BOOL=ON")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DLIBAEC_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DZLIB_USE_LOCALCONTENT:BOOL=OFF")
             set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_LOCALCONTENT:BOOL=OFF")
@@ -795,6 +801,7 @@ jobs:
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_ZLIB_SUPPORT:BOOL=ON")
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_SZIP_SUPPORT:BOOL=ON")
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_ENABLE_PLUGIN_SUPPORT:BOOL=ON")
+              set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_EXTERNAL:BOOL=ON")
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DLIBAEC_USE_LOCALCONTENT:BOOL=OFF")
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DZLIB_USE_LOCALCONTENT:BOOL=OFF")
               set (ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DPLUGIN_USE_LOCALCONTENT:BOOL=OFF")
diff --git a/CMakePlugins.cmake b/CMakePlugins.cmake
index 6d17ad99b14..408bfb356ae 100644
--- a/CMakePlugins.cmake
+++ b/CMakePlugins.cmake
@@ -141,7 +141,8 @@ function (external_hdf5_plugins_library)
   # Include HDF5 filter plugins CMake cache configuration
   include (${HDF_RESOURCES_DIR}/HDF5PluginCache.cmake)
 
-  # Set other options for build
+  # Set other options for build. Set CMake policy CMP0077 so that option()
+  # commands in Blosc(2) don't override values we set here
   set (CMAKE_POLICY_DEFAULT_CMP0077 NEW)
 
   if (HDF5_ALLOW_EXTERNAL_SUPPORT MATCHES "GIT" OR NOT PLUGIN_USE_LOCALCONTENT)
@@ -150,11 +151,18 @@ function (external_hdf5_plugins_library)
     message (VERBOSE "Configuring HDF5 filter plugins project")
   endif ()
 
+  # If building zlib externally when building HDF5, instruct Blosc(2) to prefer
+  # using a system zlib for building so that it doesn't build its own zlib that
+  # will conflict with the one HDF5 will build.
+  if (HDF5_ENABLE_ZLIB_SUPPORT AND ZLIB_USE_EXTERNAL)
+    set (PREFER_EXTERNAL_ZLIB ON)
+  endif ()
+
   # Make HDF5 filter plugins project available for the build
   FetchContent_MakeAvailable (HDF5_FILTER_PLUGINS)
 
   # Set HDF5 filter plugins directory and status variables
-  set (PLUGIN_BINARY_DIR "${plugin_BINARY_DIR}" PARENT_SCOPE)
+  set (PLUGIN_BINARY_DIR "${hdf5_filter_plugins_BINARY_DIR}" PARENT_SCOPE)
 
   set (HDF5_PLUGINS_FOUND TRUE PARENT_SCOPE)
 endfunction ()
diff --git a/CMakePresets.json b/CMakePresets.json
index 2c4d58a9c87..fb4609cf44a 100644
--- a/CMakePresets.json
+++ b/CMakePresets.json
@@ -220,7 +220,9 @@
         "HDF5_FILTER_PLUGINS_TGZ_NAME": {
           "type": "STRING",
           "value": "hdf5_plugins-master.tar.gz"
-        }
+        },
+        "HDF_ENABLE_BLOSC_ZLIB_SUPPORT": "OFF",
+        "BLOSC_ZLIB_USE_EXTERNAL": "0"
       }
     },
     {