CI : Disable GafferArnold for pull requests from forks

In this case, the Arnold download authentication secrets aren't available, so we have no choice.

.github/workflows/main.yml

@@ -209,6 +209,12 @@ jobs:
         ARNOLD_DOWNLOAD_USER: ${{ secrets.ARNOLD_DOWNLOAD_USER }}
         ARNOLD_DOWNLOAD_PASSWORD: ${{ secrets.ARNOLD_DOWNLOAD_PASSWORD }}
       shell: python
+      # We can't build GafferArnold for pull requests from forks, because the
+      # authentication secrets for downloading Arnold aren't available (this is
+      # a GitHub security restriction). The core development team can still build
+      # GafferArnold for pull requests by pushing a branch to the main repo and
+      # making a pull request from there.
+      if: ${{ env.ARNOLD_DOWNLOAD_USER != '' }}
 
     - name: Build Docs and Package
       # Docs builds should be relatively quick. If there is a problem, this
@@ -226,7 +232,7 @@ jobs:
     - name: Validate
       run: |
         echo "::add-matcher::./.github/workflows/main/problemMatchers/validateRelease.json"
-        python ./config/validateRelease.py --archive ${{ env.GAFFER_BUILD_NAME }}.${{ env.PACKAGE_EXTENSION }} ${{ env.GAFFER_VALIDATE_EXTRA_FLAGS }}
+        python ./config/validateRelease.py --archive ${{ env.GAFFER_BUILD_NAME }}.${{ env.PACKAGE_EXTENSION }} ${{ env.GAFFER_VALIDATE_EXTRA_FLAGS }} ${{ env.ARNOLD_DOWNLOAD_USER == '' && '--skipPaths arnold' || '' }}
         echo "::remove-matcher owner=validateRelease::"
       if: matrix.publish
 

config/validateRelease.py

@@ -58,6 +58,13 @@
 	help = "If set, validation will not check for documentation in the archive"
 )
 
+parser.add_argument(
+	"--skipPaths",
+	nargs = '+',
+	default = [],
+	help = "A list of paths to skip the checks for."
+)
+
 args = parser.parse_args()
 
 if not os.path.exists( args.archive ) :
@@ -93,6 +100,10 @@
 	requiredPaths.append( os.path.join( "python", "GafferAppleseed" ) )
 	requiredPaths.append( os.path.join( "python", "%sUI" % "GafferAppleseed" ) )
 
+for path in args.skipPaths :
+	if path in requiredPaths :
+		requiredPaths.remove( path )
+
 rawMembers = []
 
 if args.archive.endswith( ".tar.gz" ) :

doc/source/Reference/NodeReference/generate.py

@@ -11,6 +11,6 @@
 	import GafferArnoldUI
 	modules = [ GafferArnold ]
 except ImportError :
-	modules = modules
+	modules = []
 
 GafferUI.DocumentationAlgo.exportNodeReference( "./", modules = modules, modulePath = "$GAFFER_ROOT/python" )