Implement WFJT prompting for limit & scm_branch

add feature to UI and awxkit

restructure some details of create_unified_job
  for workflows to allow use of char_prompts
  hidden field
avoid conflict with sliced jobs in char_prompts copy logic

update developer docs

update migration reference

bump migration

awx/main/utils/common.py

@@ -19,9 +19,14 @@ from functools import reduce, wraps
 from decimal import Decimal
 
 # Django
-from django.core.exceptions import ObjectDoesNotExist
+from django.core.exceptions import ObjectDoesNotExist, FieldDoesNotExist
 from django.utils.translation import ugettext_lazy as _
+from django.utils.functional import cached_property
 from django.db.models.fields.related import ForeignObjectRel, ManyToManyField
+from django.db.models.fields.related_descriptors import (
+    ForwardManyToOneDescriptor,
+    ManyToManyDescriptor
+)
 from django.db.models.query import QuerySet
 from django.db.models import Q
 
@@ -42,7 +47,7 @@ __all__ = ['get_object_or_400', 'camelcase_to_underscore', 'underscore_to_camelc
            'get_current_apps', 'set_current_apps',
            'extract_ansible_vars', 'get_search_fields', 'get_system_task_capacity', 'get_cpu_capacity', 'get_mem_capacity',
            'wrap_args_with_proot', 'build_proot_temp_dir', 'check_proot_installed', 'model_to_dict',
-           'model_instance_diff', 'parse_yaml_or_json', 'RequireDebugTrueOrTest',
+           'NullablePromptPsuedoField', 'model_instance_diff', 'parse_yaml_or_json', 'RequireDebugTrueOrTest',
            'has_model_field_prefetched', 'set_environ', 'IllegalArgumentError', 'get_custom_venv_choices', 'get_external_account',
            'task_manager_bulk_reschedule', 'schedule_task_manager', 'classproperty', 'create_temporary_fifo']
 
@@ -435,6 +440,39 @@ def model_to_dict(obj, serializer_mapping=None):
     return attr_d
 
 
+class CharPromptDescriptor:
+    """Class used for identifying nullable launch config fields from class
+    ex. Schedule.limit
+    """
+    def __init__(self, field):
+        self.field = field
+
+
+class NullablePromptPsuedoField:
+    """
+    Interface for psuedo-property stored in `char_prompts` dict
+    Used in LaunchTimeConfig and submodels, defined here to avoid circular imports
+    """
+    def __init__(self, field_name):
+        self.field_name = field_name
+
+    @cached_property
+    def field_descriptor(self):
+        return CharPromptDescriptor(self)
+
+    def __get__(self, instance, type=None):
+        if instance is None:
+            # for inspection on class itself
+            return self.field_descriptor
+        return instance.char_prompts.get(self.field_name, None)
+
+    def __set__(self, instance, value):
+        if value in (None, {}):
+            instance.char_prompts.pop(self.field_name, None)
+        else:
+            instance.char_prompts[self.field_name] = value
+
+
 def copy_model_by_class(obj1, Class2, fields, kwargs):
     '''
     Creates a new unsaved object of type Class2 using the fields from obj1
@@ -442,9 +480,10 @@ def copy_model_by_class(obj1, Class2, fields, kwargs):
     '''
     create_kwargs = {}
     for field_name in fields:
-        # Foreign keys can be specified as field_name or field_name_id.
-        id_field_name = '%s_id' % field_name
-        if hasattr(obj1, id_field_name):
+        descriptor = getattr(Class2, field_name)
+        if isinstance(descriptor, ForwardManyToOneDescriptor):  # ForeignKey
+            # Foreign keys can be specified as field_name or field_name_id.
+            id_field_name = '%s_id' % field_name
             if field_name in kwargs:
                 value = kwargs[field_name]
             elif id_field_name in kwargs:
@@ -454,15 +493,29 @@ def copy_model_by_class(obj1, Class2, fields, kwargs):
             if hasattr(value, 'id'):
                 value = value.id
             create_kwargs[id_field_name] = value
+        elif isinstance(descriptor, CharPromptDescriptor):
+            # difficult case of copying one launch config to another launch config
+            new_val = None
+            if field_name in kwargs:
+                new_val = kwargs[field_name]
+            elif hasattr(obj1, 'char_prompts'):
+                if field_name in obj1.char_prompts:
+                    new_val = obj1.char_prompts[field_name]
+            elif hasattr(obj1, field_name):
+                # extremely rare case where a template spawns a launch config - sliced jobs
+                new_val = getattr(obj1, field_name)
+            if new_val is not None:
+                create_kwargs.setdefault('char_prompts', {})
+                create_kwargs['char_prompts'][field_name] = new_val
+        elif isinstance(descriptor, ManyToManyDescriptor):
+            continue  # not coppied in this method
         elif field_name in kwargs:
             if field_name == 'extra_vars' and isinstance(kwargs[field_name], dict):
                 create_kwargs[field_name] = json.dumps(kwargs['extra_vars'])
             elif not isinstance(Class2._meta.get_field(field_name), (ForeignObjectRel, ManyToManyField)):
                 create_kwargs[field_name] = kwargs[field_name]
         elif hasattr(obj1, field_name):
-            field_obj = obj1._meta.get_field(field_name)
-            if not isinstance(field_obj, ManyToManyField):
-                create_kwargs[field_name] = getattr(obj1, field_name)
+            create_kwargs[field_name] = getattr(obj1, field_name)
 
     # Apply class-specific extra processing for origination of unified jobs
     if hasattr(obj1, '_update_unified_job_kwargs') and obj1.__class__ != Class2:
@@ -481,7 +534,10 @@ def copy_m2m_relationships(obj1, obj2, fields, kwargs=None):
     '''
     for field_name in fields:
         if hasattr(obj1, field_name):
-            field_obj = obj1._meta.get_field(field_name)
+            try:
+                field_obj = obj1._meta.get_field(field_name)
+            except FieldDoesNotExist:
+                continue
             if isinstance(field_obj, ManyToManyField):
                 # Many to Many can be specified as field_name
                 src_field_value = getattr(obj1, field_name)