Defer subcommand context creation until later.

This fixes a regression that was introduced with the 3.0
release.  This broke well established patters and was never
intended to break.

This fixes pallets#200

CHANGES

@@ -8,6 +8,10 @@ Version 3.1
 
 (bugfix release, release date to be decided)
 
+- Fixed a regression that caused contexts of subcommands to be
+  created before the parent command was invoked which was a
+  regression from earlier Click versions.
+
 Version 3.0
 -----------
 

click/core.py

@@ -883,33 +883,33 @@ def _process_result(value):
         # single command but we also inform the current context about the
         # name of the command to invoke.
         if not self.chain:
-            sub_ctx = self.handle_subcommand(ctx, args)
-            ctx.invoked_subcommands = [sub_ctx.info_name]
-
             # Make sure the context is entered so we do not clean up
             # resources until the result processor has worked.
             with ctx:
                 Command.invoke(self, ctx)
+                sub_ctx = self.handle_subcommand(ctx, args)
+                ctx.invoked_subcommands = [sub_ctx.info_name]
                 with sub_ctx:
                     return _process_result(sub_ctx.command.invoke(sub_ctx))
 
-        # Otherwise we make every single context and invoke them in a
-        # chain.  In that case the return value to the result processor
-        # is the list of all invoked subcommand's results.
-        contexts = []
-        while args:
-            sub_ctx = self.handle_subcommand(ctx, args, allow_extra_args=True,
-                                             allow_interspersed_args=False)
-            contexts.append(sub_ctx)
-            args = sub_ctx.args
-
-        # Now that we have all contexts, we can invoke them.
-        ctx.invoked_subcommands = [x.info_name for x in contexts]
-
         # Make sure the context is entered so we do not clean up
         # resources until the result processor has worked.
         with ctx:
             Command.invoke(self, ctx)
+
+            # Otherwise we make every single context and invoke them in a
+            # chain.  In that case the return value to the result processor
+            # is the list of all invoked subcommand's results.
+            contexts = []
+            while args:
+                sub_ctx = self.handle_subcommand(ctx, args, allow_extra_args=True,
+                                                 allow_interspersed_args=False)
+                contexts.append(sub_ctx)
+                args = sub_ctx.args
+
+            # Now that we have all contexts, we can invoke them.
+            ctx.invoked_subcommands = [x.info_name for x in contexts]
+
             rv = []
             for sub_ctx in contexts:
                 with sub_ctx:

tests/test_commands.py

@@ -174,3 +174,23 @@ def test_callback(args, filename, verbose):
         '  -f FILE, --file=FILE  write report to FILE',
         '  -q, --quiet           don\'t print status messages to stdout',
     ]
+
+
+def test_object_propagation(runner):
+    for chain in False, True:
+        @click.group(chain=chain)
+        @click.option('--debug/--no-debug', default=False)
+        @click.pass_context
+        def cli(ctx, debug):
+            if ctx.obj is None:
+                ctx.obj = {}
+            ctx.obj['DEBUG'] = debug
+
+        @cli.command()
+        @click.pass_context
+        def sync(ctx):
+            click.echo('Debug is %s' % (ctx.obj['DEBUG'] and 'on' or 'off'))
+
+        result = runner.invoke(cli, ['sync'])
+        assert result.exception is None
+        assert result.output == 'Debug is off\n'