Fix traceback with `only` directives preceded by targets.

CHANGES

@@ -1,6 +1,8 @@
 Release 1.0.7 (in development)
 ==============================
 
+* Fix traceback with ``only`` directives preceded by targets.
+
 * Fix tracebacks occurring for duplicate C++ domain objects.
 
 

sphinx/environment.py

@@ -1363,7 +1363,9 @@ class BuildEnvironment:
                 if ret:
                     node.replace_self(node.children)
                 else:
-                    node.replace_self([])
+                    # replacing by [] would result in an "Losing ids" exception
+                    # if there is a target node before the only node
+                    node.replace_self(nodes.comment())
 
         # allow custom references to be resolved
         builder.app.emit('doctree-resolved', doctree, fromdocname)