feat(schema): support for 'variant' schema

Documentation links, at one spot, have been updated as well.
The variant schema is represented natively as enum, it all looks
very good.

Json has been taken care of as well ... .

src/mako/lib/lib.mako

@@ -5,7 +5,7 @@
                       find_fattest_resource, build_all_params, pass_through, parts_from_params,
                       REQUEST_MARKER_TRAIT, RESPONSE_MARKER_TRAIT, supports_scopes, to_api_version,
                       to_fqan, METHODS_RESOURCE, ADD_PARAM_MEDIA_EXAMPLE, PROTOCOL_TYPE_INFO, enclose_in,
-                      upload_action_fn, unique_type_name)  %>\
+                      upload_action_fn, unique_type_name, schema_doc_format)  %>\
 <%namespace name="util" file="util.mako"/>\
 <%namespace name="mbuild" file="mbuild.mako"/>\
 
@@ -78,7 +78,7 @@ It seems there is nothing you can do here ... .
     sn = singular(canonical_type_name(r))
 
     if sn in schemas:
-        md_resource = link(md_resource, 'struct.%s.html' % unique_type_name(singular(canonical_type_name(r))))
+        md_resource = link(md_resource, schema_doc_format(schemas[sn]) % unique_type_name(sn))
 %>\
 * ${md_resource} (${put_and(md_methods)})
 % endfor ## each resource activity

src/mako/lib/schema.mako

@@ -2,7 +2,7 @@
     from util import (schema_markers, rust_doc_comment, mangle_ident, to_rust_type, put_and, 
                       IO_TYPES, activity_split, enclose_in, REQUEST_MARKER_TRAIT, mb_type, indent_all_but_first_by,
                       NESTED_TYPE_SUFFIX, RESPONSE_MARKER_TRAIT, split_camelcase_s, METHODS_RESOURCE, unique_type_name, 
-                      PART_MARKER_TRAIT) 
+                      PART_MARKER_TRAIT, canonical_type_name)
 
     default_traits = ('RustcEncodable', 'Clone', 'Default')
 %>\
@@ -23,6 +23,26 @@ ${struct} {
 }
 % elif 'additionalProperties' in s:
 ${struct}(${to_rust_type(schemas, s.id, NESTED_TYPE_SUFFIX, s, allow_optionals=allow_optionals)});
+% elif 'variant' in s:
+<% 
+    et = unique_type_name(s.id)
+    variant_type = lambda p: canonical_type_name(p.type_value)
+%>
+pub enum ${et} {
+% for p in s.variant.map:
+    ${p.get('description', 'no description provided') | rust_doc_comment, indent_all_but_first_by(1)}
+    % if variant_type(p) != p.type_value:
+    #[serde(alias="${p.type_value}")]
+    % endif
+    ${variant_type(p)}(${to_rust_type(schemas, s.id, None, p, allow_optionals=allow_optionals)}),
+% endfor
+}
+
+impl Default for ${et} {
+    fn default() -> ${et} {
+        ${et}::${variant_type(s.variant.map[0])}(Default::default())
+    }
+}
 % else: ## it's an empty struct, i.e. struct Foo;
 ${struct};
 % endif ## 'properties' in s
@@ -35,7 +55,11 @@ ${struct};
 <%def name="new(s, c)">\
 <% 
     markers = schema_markers(s, c, transitive=True)
-    traits = ['Default', 'Clone', 'Debug']
+    traits = ['Clone', 'Debug']
+
+    # default only works for structs, and 'variant' will be an enum
+    if 'variant' not in s:
+        traits.insert(0, 'Default')
     
     allow_optionals = True
     if REQUEST_MARKER_TRAIT in markers:

src/mako/lib/util.py

@@ -506,6 +506,13 @@ def rust_copy_value_s(n, tn, p):
 def schema_to_required_property(s, n):
     return type(s)({'name': n, TREF: s.id, 'priority': REQUEST_PRIORITY, 'is_query_param': False})
 
+# Return relative URL format to the given schema. Handles structs and enums accordingly
+def schema_doc_format(s):
+    prefix = 'struct.'
+    if 'variant' in s:
+        prefix = 'enum.'
+    return prefix + '%s.html'
+
 def is_required_property(p):
     return p.get('required', False) or p.get('priority', 0) > 0
 
@@ -689,6 +696,9 @@ def new_context(schemas, resources, methods):
                 elif 'items' in p:
                     recurse_properties(nested_type_name(prefix, pn), rs, 
                                                         p.items, append_unique(parent_ids, rs.id))
+                elif 'variant' in p:
+                    for enum in p.variant.map:
+                        recurse_properties(prefix, rs, enum, parent_ids)
                 # end handle prop itself
             # end for each property
         # end utility