POC: Add option to disable Classic UI.

Products/CMFPlone/_disable_classic_ui.py

@@ -0,0 +1,75 @@
+"""Hang on, this is funny.
+
+The summary is: if you want to (partially) disable Classic UI,
+you can set an environment variable DISABLE_CLASSIC_UI=true.
+This is a temporary measure for Plone 6.1+.
+In Plone 7, Classic UI would be disabled by default,
+unless the plone.classicui package is available.
+
+How does this work?
+
+In meta.zcml, we check if this module can be imported.
+If the import works, we register a zcml feature "disable-classic-ui".
+If the import doesn't work, we do nothing, and all is normal.
+
+In this module, we check for an environment variable DISABLE_CLASSIC_UI.
+We check if this has been set, and has a "truthy" value.
+
+If it is truthy, we do nothing.
+Result: this module can be imported.
+
+If it is not set, or not truthy, we raise an ImportError.
+Result: this module can't be imported.
+This is actually the expected default case in Plone 6.
+
+Now we can use zcml:condition="not-have disable-classic-ui"
+around zcml parts that load zcml that is only of interest for Classic UI.
+
+Some potential targets:
+
+* portlets
+* viewlets
+* plonetheme.barceloneta
+* plone.staticresources
+
+In the first tests with portlets, we can see that it can be tricky to get this right.
+
+* We can avoid loading the zcml of plone.portlets, plone.app.portlets,
+  and plone.portlet.static/collection in CMFPlone, but plone.portlet.static
+  has autoinclude of its zcml turned on setup.py, and loading it fails.
+  This is something to fix in plone.portlet.static.
+* plone.app.event defines two own portlets, so it needs to use the same
+  conditional loading of this part of its zcml.
+* The rolemap.xml of CMFPlone wants to set roles for a permission
+  "Portlets: Manage portlets" and this fails unless we load the
+  permissions.zcml from plone.app.portlets anyway.
+* In metadata.xml of the CMFPlone dependencies profile, we want to install
+  the default profiles of plone.portlet.collection/static, which fails.
+  A solution would be to integrate the portlets.xml from these two packages in our own.
+* Note that it is fine that CMFPlone has a portlets.xml: if the plone.app.portlets
+  zcml is not loaded, no import handler is defined that reads this.
+* plone.app.contentmenu defines a Portlets menu, which leads to non-existing urls.
+  The contentmenu is specific for Classic UI though, so we might want to avoid
+  loading this as well.
+* Obviously lots of tests will fail.
+  Nicest would be to have an extra job on Jenkins or GitHub Actions that installs
+  only Products.CMFPlone and its test dependencies, and disable Classic UI there,
+  and run the tests.
+* It might be easier to first "unify" the portlets:
+  * Move the portlets from plone.portlet.collection/static and plone.app.event
+    to plone.app.portlets.
+  * Keep BBB imports in place, to avoid breaking existing portlets.
+  * Be careful to not introduce circular imports.
+  * Move portlets.xml from CMFPlone to plone.app.portlets in a new profile.
+  * Move the portlet part of rolemap.xml to plone.app.portlets.
+  * Make sure to install the new profile by default: we only want to change
+    this in Plone 7.
+* Perhaps disabling plone.app.layout.viewlets is an easier first target
+  for disabling a part of Classic UI. :-)
+
+"""
+import os
+
+
+if os.getenv("DISABLE_CLASSIC_UI", "").lower() not in ("true", "yes", "on", "1"):
+    raise ImportError("Explicitly raised ImportError to disable Classic UI.")

Products/CMFPlone/configure.zcml

@@ -26,7 +26,6 @@
   <include package="plone.locking" />
   <include package="plone.memoize" />
   <include package="plone.outputfilters" />
-  <include package="plone.portlets" />
   <include package="plone.protect" />
   <include package="plone.registry" />
   <include package="plone.resource" />
@@ -50,7 +49,6 @@
   <include package="plone.app.linkintegrity" />
   <include package="plone.app.locales" />
   <include zcml:condition="installed plone.app.multilingual" package="plone.app.multilingual" />
-  <include package="plone.app.portlets" />
   <include package="plone.app.redirector" />
   <include package="plone.app.registry" />
   <include package="plone.app.theming" />
@@ -61,8 +59,17 @@
   <include package="plone.app.workflow" />
 
   <!-- plone extra -->
-  <include package="plone.portlet.static" />
-  <include package="plone.portlet.collection" />
+  <configure zcml:condition="not-have disable-classic-ui">
+    <include zcml:condition="installed plone.portlets" package="plone.portlets" />
+    <include zcml:condition="installed plone.app.portlets" package="plone.app.portlets" />
+    <include zcml:condition="installed plone.portlet.static" package="plone.portlet.static" />
+    <include zcml:condition="installed plone.portlet.collection" package="plone.portlet.collection" />
+  </configure>
+  <configure zcml:condition="have disable-classic-ui">
+    <!-- We must include this, otherwise the CMFPlone rolemap.xml cannot be imported. -->
+    <include package="plone.app.portlets" file="permissions.zcml" />
+  </configure>
+
   <include package="plonetheme.barceloneta" />
 
   <!-- conditional -->

Products/CMFPlone/meta.zcml

@@ -21,6 +21,14 @@
   <meta:provides feature="plone-52" />
   <meta:provides feature="plone-60" />
   <meta:provides feature="plone-61" />
+  <!-- XXX plone.portlet.static has autoinclude, which does not help here.
+       So temporarily switch this off.
+       See remarks in _disable_classic_ui.py -->
+  <meta:provides feature="disable-autoinclude" />
+
+  <configure zcml:condition="installed Products.CMFPlone._disable_classic_ui">
+    <meta:provides feature="disable-classic-ui" />
+  </configure>
 
   <include
       package="Products.CMFCore"
@@ -43,10 +51,13 @@
       package="plone.app.dexterity"
       file="meta.zcml"
       />
-  <include
-      package="plone.app.portlets"
-      file="meta.zcml"
-      />
+  <configure zcml:condition="not-have disable-classic-ui">
+    <include
+        package="plone.app.portlets"
+        file="meta.zcml"
+        zcml:condition="installed plone.app.portlets"
+        />
+  </configure>
   <include
       package="plone.contentrules"
       file="meta.zcml"

Products/CMFPlone/overrides.zcml

@@ -17,12 +17,16 @@
       package="plone.i18n"
       file="overrides.zcml"
       />
+  <configure zcml:condition="not-have disable-classic-ui">
+    <include package="disable.override" />
+    <include
+        package="plone.app.portlets"
+        file="overrides.zcml"
+        zcml:condition="installed plone.app.portlets"
+        />
+  </configure>
   <include
-      package="plone.app.portlets"
-      file="overrides.zcml"
-      />
-  <include
-      zcml:condition="installed plone.app.multilingual"     
+      zcml:condition="installed plone.app.multilingual"
       package="plone.app.multilingual"
       file="overrides.zcml"
       />

Products/CMFPlone/profiles/dependencies/metadata.xml

@@ -12,8 +12,9 @@
     <dependency>profile-plone.app.theming:default</dependency>
     <dependency>profile-plone.app.users:default</dependency>
     <dependency>profile-plone.outputfilters:default</dependency>
-    <dependency>profile-plone.portlet.collection:default</dependency>
-    <dependency>profile-plone.portlet.static:default</dependency>
+    <!-- TODO Integrate the portlets.xml from these two packages in our own. -->
+    <!-- <dependency>profile-plone.portlet.collection:default</dependency> -->
+    <!-- <dependency>profile-plone.portlet.static:default</dependency> -->
     <dependency>profile-plone.protect:default</dependency>
     <dependency>profile-plone.staticresources:default</dependency>
   </dependencies>