Only resolve ids in known keywords

It looks like we were too permissive in: #71

This addresses issues from:

- json-schema-org/JSON-Schema-Test-Suite#471
- json-schema-org/JSON-Schema-Test-Suite#484

The first issue is more important, I think. We were resolving `$id` in
keywords like `enum` and `const`, which is unexpected since those values
are literal.

The second issue is a little trickier. It's possible people are using
non-standard keys to store reference schemas, which will cause issues
since this only looks in `definitions` now.

Author: davishmcclurg

lib/json_schemer/schema/base.rb

@@ -645,13 +645,21 @@ def resolve_ids(schema, ids = {}, parent_uri = nil, pointer = '')
         elsif schema.is_a?(Hash)
           uri = join_uri(parent_uri, schema[id_keyword])
           schema.each do |key, value|
-            if key == id_keyword && uri != parent_uri
-              ids[uri.to_s] = {
-                schema: schema,
-                pointer: pointer
-              }
+            case key
+            when id_keyword
+              unless uri == parent_uri
+                ids[uri.to_s] = {
+                  schema: schema,
+                  pointer: pointer
+                }
+              end
+            when 'items', 'allOf', 'anyOf', 'oneOf', 'additionalItems', 'contains', 'additionalProperties', 'propertyNames', 'if', 'then', 'else', 'not'
+              resolve_ids(value, ids, uri, "#{pointer}/#{key}")
+            when 'properties', 'patternProperties', 'definitions', 'dependencies'
+              value.each do |subkey, subvalue|
+                resolve_ids(subvalue, ids, uri, "#{pointer}/#{key}/#{subkey}")
+              end
             end
-            resolve_ids(value, ids, uri, "#{pointer}/#{key}")
           end
         end
         ids

test/json_schemer_test.rb

@@ -522,7 +522,7 @@ def test_it_returns_correct_pointers_for_ref_id
 
   def test_can_refer_to_subschemas_inside_hashes
     root = {
-     'foo' => {
+     'definitions' => {
         'bar' => {
           '$id' => '#bar',
           'type' => 'string'
@@ -537,17 +537,17 @@ def test_can_refer_to_subschemas_inside_hashes
     assert errors.first == {
       'data' => 42,
       'data_pointer' => '',
-      'schema' => root['foo']['bar'],
-      'schema_pointer' => '/foo/bar',
+      'schema' => root['definitions']['bar'],
+      'schema_pointer' => '/definitions/bar',
       'root_schema' => root,
       'type' => 'string'
     }
   end
 
   def test_can_refer_to_subschemas_inside_arrays
     root = {
-     'foo' => [{
-        'bar' => {
+     'allOf' => [{
+        'if' => {
           '$id' => '#bar',
           'type' => 'string'
         }
@@ -565,8 +565,8 @@ def test_can_refer_to_subschemas_inside_arrays
     assert errors.first == {
       'data' => 1,
       'data_pointer' => '/a/x',
-      'schema' => root['foo'].first['bar'],
-      'schema_pointer' => '/foo/0/bar',
+      'schema' => root['allOf'].first['if'],
+      'schema_pointer' => '/allOf/0/if',
       'root_schema' => root,
       'type' => 'string'
     }
@@ -575,7 +575,7 @@ def test_can_refer_to_subschemas_inside_arrays
   def test_can_refer_to_subschemas_in_hash_with_remote_pointer
     ref_schema = {
       '$id' => 'http://example.com/ref_schema.json',
-      'foo' => {
+      'definitions' => {
         'bar' => {
           '$id' => '#bar',
           'type' => 'string'
@@ -599,8 +599,8 @@ def test_can_refer_to_subschemas_in_hash_with_remote_pointer
     assert errors.first == {
       'data' => 1,
       'data_pointer' => '/a/x',
-      'schema' => ref_schema['foo']['bar'],
-      'schema_pointer' => '/foo/bar',
+      'schema' => ref_schema['definitions']['bar'],
+      'schema_pointer' => '/definitions/bar',
       'root_schema' => ref_schema,
       'type' => 'string'
     }
@@ -609,18 +609,16 @@ def test_can_refer_to_subschemas_in_hash_with_remote_pointer
   def test_can_refer_to_multiple_subschemas_in_hash
     ref_schema = {
       '$id' => 'http://example.com/ref_schema.json',
-      'types' => {
+      'definitions' => {
         'uuid' => {
            '$id' => "#uuid",
            'type' => 'string',
            'pattern' => "^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$"
         }
       },
-      'foo' => {
-        'bar' => {
-          '$id' => '#bar',
-          'allOf' => [{ "$ref" => "#uuid"}]
-        }
+      'not' => {
+        '$id' => '#bar',
+        'allOf' => [{ "$ref" => "#uuid"}]
       }
     }
     root = {
@@ -640,8 +638,8 @@ def test_can_refer_to_multiple_subschemas_in_hash
     assert errors.first == {
       'data' => "1122-112",
       'data_pointer' => '/a/x',
-      'schema' => ref_schema['types']['uuid'],
-      'schema_pointer' => '/types/uuid',
+      'schema' => ref_schema['definitions']['uuid'],
+      'schema_pointer' => '/definitions/uuid',
       'root_schema' => ref_schema,
       'type' => 'pattern'
     }