perf(oas2): cache body generation for allOf's with ref

Author: kylef

packages/openapi2-parser/CHANGELOG.md

@@ -1,5 +1,13 @@
 # API Elements: OpenAPI 2 Parser Changelog
 
+## Master
+
+### Bug Fixes
+
+- This release includes performance improvements to parsing documents which
+  contain the same schema re-used via a reference (`$ref`) many times in
+  request parameters and response bodies under an `allOf` key.
+
 ## 0.31.0 (2020-05-12)
 
 ### Bug Fixes

packages/openapi2-parser/lib/parser.js

@@ -1611,7 +1611,16 @@ class Parser {
     const referencedPathValue = this.referencedPathValue();
     let cacheKey;
     if (referencedPathValue && referencedPathValue.$ref) {
+      // schema object with $ref
       cacheKey = `${referencedPathValue.$ref};${contentType}`;
+    } else if (
+      referencedPathValue
+      && referencedPathValue.allOf
+      && Object.keys(referencedPathValue).length === 1
+      && referencedPathValue.allOf.length === 1
+      && referencedPathValue.allOf[0].$ref) {
+      // schema object with single ref in allOf (`allOf: [{$ref: path}]`)
+      cacheKey = `${referencedPathValue.allOf[0].$ref};${contentType}`;
     }
 
     if (this.generateMessageBody || this.generateMessageBodySchema) {