Improve RelatedField and callable default handling

- callable default values will now be properly called 
  - PrimaryKeyRelatedField and SlugRelatedField will now return an appropriate type based on the relation model's Field
  - mock views now have a request object bound even when public is True

testproj/snippets/migrations/0001_initial.py

@@ -1,8 +1,8 @@
-# -*- coding: utf-8 -*-
-# Generated by Django 1.11.7 on 2017-11-29 21:28
-from __future__ import unicode_literals
+# Generated by Django 2.0 on 2017-12-23 09:07
 
+from django.conf import settings
 from django.db import migrations, models
+import django.db.models.deletion
 
 
 class Migration(migrations.Migration):
@@ -10,6 +10,7 @@ class Migration(migrations.Migration):
     initial = True
 
     dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
     ]
 
     operations = [
@@ -19,10 +20,11 @@ class Migration(migrations.Migration):
                 ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                 ('created', models.DateTimeField(auto_now_add=True)),
                 ('title', models.CharField(blank=True, default='', max_length=100)),
-                ('code', models.TextField()),
+                ('code', models.TextField(help_text='code model help text')),
                 ('linenos', models.BooleanField(default=False)),
                 ('language', models.CharField(choices=[('abap', 'ABAP'), ('abnf', 'ABNF'), ('ada', 'Ada'), ('adl', 'ADL'), ('agda', 'Agda'), ('aheui', 'Aheui'), ('ahk', 'autohotkey'), ('alloy', 'Alloy'), ('ampl', 'Ampl'), ('antlr', 'ANTLR'), ('antlr-as', 'ANTLR With ActionScript Target'), ('antlr-cpp', 'ANTLR With CPP Target'), ('antlr-csharp', 'ANTLR With C# Target'), ('antlr-java', 'ANTLR With Java Target'), ('antlr-objc', 'ANTLR With ObjectiveC Target'), ('antlr-perl', 'ANTLR With Perl Target'), ('antlr-python', 'ANTLR With Python Target'), ('antlr-ruby', 'ANTLR With Ruby Target'), ('apacheconf', 'ApacheConf'), ('apl', 'APL'), ('applescript', 'AppleScript'), ('arduino', 'Arduino'), ('as', 'ActionScript'), ('as3', 'ActionScript 3'), ('aspectj', 'AspectJ'), ('aspx-cs', 'aspx-cs'), ('aspx-vb', 'aspx-vb'), ('asy', 'Asymptote'), ('at', 'AmbientTalk'), ('autoit', 'AutoIt'), ('awk', 'Awk'), ('basemake', 'Base Makefile'), ('bash', 'Bash'), ('bat', 'Batchfile'), ('bbcode', 'BBCode'), ('bc', 'BC'), ('befunge', 'Befunge'), ('bib', 'BibTeX'), ('blitzbasic', 'BlitzBasic'), ('blitzmax', 'BlitzMax'), ('bnf', 'BNF'), ('boo', 'Boo'), ('boogie', 'Boogie'), ('brainfuck', 'Brainfuck'), ('bro', 'Bro'), ('bst', 'BST'), ('bugs', 'BUGS'), ('c', 'C'), ('c-objdump', 'c-objdump'), ('ca65', 'ca65 assembler'), ('cadl', 'cADL'), ('camkes', 'CAmkES'), ('capdl', 'CapDL'), ('capnp', "Cap'n Proto"), ('cbmbas', 'CBM BASIC V2'), ('ceylon', 'Ceylon'), ('cfc', 'Coldfusion CFC'), ('cfengine3', 'CFEngine3'), ('cfm', 'Coldfusion HTML'), ('cfs', 'cfstatement'), ('chai', 'ChaiScript'), ('chapel', 'Chapel'), ('cheetah', 'Cheetah'), ('cirru', 'Cirru'), ('clay', 'Clay'), ('clean', 'Clean'), ('clojure', 'Clojure'), ('clojurescript', 'ClojureScript'), ('cmake', 'CMake'), ('cobol', 'COBOL'), ('cobolfree', 'COBOLFree'), ('coffee-script', 'CoffeeScript'), ('common-lisp', 'Common Lisp'), ('componentpascal', 'Component Pascal'), ('console', 'Bash Session'), ('control', 'Debian Control file'), ('coq', 'Coq'), ('cpp', 'C++'), ('cpp-objdump', 'cpp-objdump'), ('cpsa', 'CPSA'), ('cr', 'Crystal'), ('crmsh', 'Crmsh'), ('croc', 'Croc'), ('cryptol', 'Cryptol'), ('csharp', 'C#'), ('csound', 'Csound Orchestra'), ('csound-document', 'Csound Document'), ('csound-score', 'Csound Score'), ('css', 'CSS'), ('css+django', 'CSS+Django/Jinja'), ('css+erb', 'CSS+Ruby'), ('css+genshitext', 'CSS+Genshi Text'), ('css+lasso', 'CSS+Lasso'), ('css+mako', 'CSS+Mako'), ('css+mozpreproc', 'CSS+mozpreproc'), ('css+myghty', 'CSS+Myghty'), ('css+php', 'CSS+PHP'), ('css+smarty', 'CSS+Smarty'), ('cucumber', 'Gherkin'), ('cuda', 'CUDA'), ('cypher', 'Cypher'), ('cython', 'Cython'), ('d', 'D'), ('d-objdump', 'd-objdump'), ('dart', 'Dart'), ('delphi', 'Delphi'), ('dg', 'dg'), ('diff', 'Diff'), ('django', 'Django/Jinja'), ('docker', 'Docker'), ('doscon', 'MSDOS Session'), ('dpatch', 'Darcs Patch'), ('dtd', 'DTD'), ('duel', 'Duel'), ('dylan', 'Dylan'), ('dylan-console', 'Dylan session'), ('dylan-lid', 'DylanLID'), ('earl-grey', 'Earl Grey'), ('easytrieve', 'Easytrieve'), ('ebnf', 'EBNF'), ('ec', 'eC'), ('ecl', 'ECL'), ('eiffel', 'Eiffel'), ('elixir', 'Elixir'), ('elm', 'Elm'), ('emacs', 'EmacsLisp'), ('erb', 'ERB'), ('erl', 'Erlang erl session'), ('erlang', 'Erlang'), ('evoque', 'Evoque'), ('extempore', 'xtlang'), ('ezhil', 'Ezhil'), ('factor', 'Factor'), ('fan', 'Fantom'), ('fancy', 'Fancy'), ('felix', 'Felix'), ('fish', 'Fish'), ('flatline', 'Flatline'), ('forth', 'Forth'), ('fortran', 'Fortran'), ('fortranfixed', 'FortranFixed'), ('foxpro', 'FoxPro'), ('fsharp', 'FSharp'), ('gap', 'GAP'), ('gas', 'GAS'), ('genshi', 'Genshi'), ('genshitext', 'Genshi Text'), ('glsl', 'GLSL'), ('gnuplot', 'Gnuplot'), ('go', 'Go'), ('golo', 'Golo'), ('gooddata-cl', 'GoodData-CL'), ('gosu', 'Gosu'), ('groff', 'Groff'), ('groovy', 'Groovy'), ('gst', 'Gosu Template'), ('haml', 'Haml'), ('handlebars', 'Handlebars'), ('haskell', 'Haskell'), ('haxeml', 'Hxml'), ('hexdump', 'Hexdump'), ('hsail', 'HSAIL'), ('html', 'HTML'), ('html+cheetah', 'HTML+Cheetah'), ('html+django', 'HTML+Django/Jinja'), ('html+evoque', 'HTML+Evoque'), ('html+genshi', 'HTML+Genshi'), ('html+handlebars', 'HTML+Handlebars'), ('html+lasso', 'HTML+Lasso'), ('html+mako', 'HTML+Mako'), ('html+myghty', 'HTML+Myghty'), ('html+ng2', 'HTML + Angular2'), ('html+php', 'HTML+PHP'), ('html+smarty', 'HTML+Smarty'), ('html+twig', 'HTML+Twig'), ('html+velocity', 'HTML+Velocity'), ('http', 'HTTP'), ('hx', 'Haxe'), ('hybris', 'Hybris'), ('hylang', 'Hy'), ('i6t', 'Inform 6 template'), ('idl', 'IDL'), ('idris', 'Idris'), ('iex', 'Elixir iex session'), ('igor', 'Igor'), ('inform6', 'Inform 6'), ('inform7', 'Inform 7'), ('ini', 'INI'), ('io', 'Io'), ('ioke', 'Ioke'), ('irc', 'IRC logs'), ('isabelle', 'Isabelle'), ('j', 'J'), ('jags', 'JAGS'), ('jasmin', 'Jasmin'), ('java', 'Java'), ('javascript+mozpreproc', 'Javascript+mozpreproc'), ('jcl', 'JCL'), ('jlcon', 'Julia console'), ('js', 'JavaScript'), ('js+cheetah', 'JavaScript+Cheetah'), ('js+django', 'JavaScript+Django/JiLine truncated
                 ('style', models.CharField(choices=[('abap', 'abap'), ('algol', 'algol'), ('algol_nu', 'algol_nu'), ('arduino', 'arduino'), ('autumn', 'autumn'), ('borland', 'borland'), ('bw', 'bw'), ('colorful', 'colorful'), ('default', 'default'), ('emacs', 'emacs'), ('friendly', 'friendly'), ('fruity', 'fruity'), ('igor', 'igor'), ('lovelace', 'lovelace'), ('manni', 'manni'), ('monokai', 'monokai'), ('murphy', 'murphy'), ('native', 'native'), ('paraiso-dark', 'paraiso-dark'), ('paraiso-light', 'paraiso-light'), ('pastie', 'pastie'), ('perldoc', 'perldoc'), ('rainbow_dash', 'rainbow_dash'), ('rrt', 'rrt'), ('tango', 'tango'), ('trac', 'trac'), ('vim', 'vim'), ('vs', 'vs'), ('xcode', 'xcode')], default='friendly', max_length=100)),
+                ('owner', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='snippets', to=settings.AUTH_USER_MODEL)),
             ],
             options={
                 'ordering': ('created',),

testproj/snippets/migrations/0002_auto_20171205_0505.py

@@ -1,27 +0,0 @@
-# Generated by Django 2.0 on 2017-12-05 04:05
-
-from django.conf import settings
-from django.db import migrations, models
-import django.db.models.deletion
-
-
-class Migration(migrations.Migration):
-
-    dependencies = [
-        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
-        ('snippets', '0001_initial'),
-    ]
-
-    operations = [
-        migrations.AddField(
-            model_name='snippet',
-            name='owner',
-            field=models.ForeignKey(default='', on_delete=django.db.models.deletion.CASCADE, related_name='snippets', to=settings.AUTH_USER_MODEL),
-            preserve_default=False,
-        ),
-        migrations.AlterField(
-            model_name='snippet',
-            name='code',
-            field=models.TextField(help_text='code model help text'),
-        ),
-    ]

testproj/snippets/serializers.py

@@ -1,3 +1,4 @@
+from django.contrib.auth import get_user_model
 from rest_framework import serializers
 
 from snippets.models import Snippet, LANGUAGE_CHOICES, STYLE_CHOICES
@@ -23,7 +24,18 @@ class SnippetSerializer(serializers.Serializer):
     create: docstring for create from serializer classdoc
     """
     id = serializers.IntegerField(read_only=True, help_text="id serializer help text")
-    owner = serializers.ReadOnlyField(source='owner.username')
+    owner = serializers.PrimaryKeyRelatedField(
+        queryset=get_user_model().objects.all(),
+        default=serializers.CurrentUserDefault(),
+        help_text="The ID of the user that created this snippet; if none is provided, "
+                  "defaults to the currently logged in user."
+    )
+    owner_as_string = serializers.PrimaryKeyRelatedField(
+        help_text="The ID of the user that created this snippet.",
+        pk_field=serializers.CharField(help_text="this help text should not show up"),
+        read_only=True,
+        source='owner',
+    )
     title = serializers.CharField(required=False, allow_blank=True, max_length=100)
     code = serializers.CharField(style={'base_template': 'textarea.html'})
     linenos = serializers.BooleanField(required=False)
@@ -31,7 +43,8 @@ class SnippetSerializer(serializers.Serializer):
     styles = serializers.MultipleChoiceField(choices=STYLE_CHOICES, default=['friendly'])
     lines = serializers.ListField(child=serializers.IntegerField(), allow_empty=True, allow_null=True, required=False)
     example_projects = serializers.ListSerializer(child=ExampleProjectSerializer(), read_only=True)
-    difficulty_factor = serializers.FloatField(help_text="this is here just to test FloatField", read_only=True)
+    difficulty_factor = serializers.FloatField(help_text="this is here just to test FloatField",
+                                               read_only=True, default=lambda: 6.9)
 
     def create(self, validated_data):
         """
@@ -39,6 +52,7 @@ class SnippetSerializer(serializers.Serializer):
         """
         del validated_data['styles']
         del validated_data['lines']
+        del validated_data['difficulty_factor']
         return Snippet.objects.create(**validated_data)
 
     def update(self, instance, validated_data):