fix for resolving looping relative references

In vacuum, a usecase was reported where an infinite loop occurred due to re-parsing the same reference over and over in a loop. It was re-creatable and it was because the loop happened before the index was ready.

This should be resolved now, at least for this use case. To be sure, I have included the specs as a new test.

https://github.com/daveshanley/vacuum/issues/268
Signed-off-by: Dave Shanley <dave@quobix.com>

test_specs/first.yaml

@@ -0,0 +1,33 @@
+openapi: 3.0.0
+info:
+  title: title
+  description: description
+  version: 0.0.0
+
+paths:
+
+  /items:
+    get:
+      tags:
+        - items
+      summary: summary
+      description: description
+      parameters: []
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                title: Schema
+                description: description
+                type: object
+
+                additionalProperties:
+                  type: object
+                  title: first title
+                  description: first description
+                  additionalProperties: false
+                  properties:
+                    second:
+                      $ref: "second.yaml"

test_specs/second.yaml

@@ -0,0 +1,31 @@
+title: second doc title
+description: second doc description
+type: object
+
+additionalProperties: false
+
+properties:
+
+  property1:
+    title: title
+    description: property 1 description
+    type: array
+    items:
+      title: item
+      description: third description
+      type: object
+      additionalProperties: false
+      properties:
+        details:
+          $ref: "third.yaml"
+
+  property2:
+    title: title
+    description: property 2 description
+    type: object
+    additionalProperties: false
+    properties:
+      property:
+        title: title
+        description: tasty description
+        type: integer

test_specs/third.yaml

@@ -0,0 +1,15 @@
+title: third doc title
+description: third doc description
+type: object
+
+additionalProperties: false
+maxProperties: 1
+
+properties:
+
+  property:
+    title: title of third prop in third doc
+    type: object
+    properties:
+      statistics:
+        $ref: 'second.yaml#/properties/property2'