fix(oas3): disallow non-string text examples

Author: kylef

packages/openapi3-parser/CHANGELOG.md

@@ -1,5 +1,14 @@
 # API Elements: OpenAPI 3 Parser Changelog
 
+## Master
+
+### Bug Fixes
+
+- Return a warning when parsing a document with a 'Media Type Object'
+  using a text based media type when the example value is not a string.
+  Previously an invalid asset element was created which contained non-string
+  content.
+
 ## 0.14.2 (2020-07-20)
 
 ### Bug Fixes

packages/openapi3-parser/lib/parser/oas/parseMediaTypeObject.js

@@ -3,7 +3,7 @@ const contentTyper = require('content-type');
 const mediaTyper = require('media-typer');
 const pipeParseResult = require('../../pipeParseResult');
 const {
-  isExtension, hasKey, getKey, getValue,
+  isString, isExtension, hasKey, getKey, getValue,
 } = require('../../predicates');
 const {
   createWarning,
@@ -89,19 +89,28 @@ const createTextMessageBodyAsset = R.curry((namespace, mediaType, value) => {
   return asset;
 });
 
-function parseExample(namespace, mediaType) {
-  const createExampleNotJSONWarning = createWarning(namespace,
+function parseExample(context, mediaType) {
+  const { namespace } = context;
+
+  const createExampleNotSupportedForMediaTypeWarning = createWarning(namespace,
     `'${name}' 'example' is not supported for media type '${mediaType}'`);
 
+  const createExampleNotStringWarning = createWarning(namespace,
+    `'${name}' 'example' should be a string for media type '${mediaType}'`);
+
   const isTextBasedType = R.anyPass([
     () => isTextMediaType(mediaType),
     () => isXMLMediaType(mediaType),
   ]);
 
+  const parseTextExample = pipeParseResult(namespace,
+    R.unless(isString, createExampleNotStringWarning),
+    createTextMessageBodyAsset(namespace, mediaType));
+
   return R.compose(R.cond([
     [() => isJSONMediaType(mediaType), createJSONMessageBodyAsset(namespace, mediaType)],
-    [() => isTextBasedType(mediaType), createTextMessageBodyAsset(namespace, mediaType)],
-    [R.T, createExampleNotJSONWarning],
+    [() => isTextBasedType(mediaType), parseTextExample],
+    [R.T, createExampleNotSupportedForMediaTypeWarning],
   ]), getValue);
 }
 
@@ -167,7 +176,7 @@ function parseMediaTypeObject(context, MessageBodyClass, element) {
     createJSONMessageBodyAsset(namespace, mediaType));
 
   const parseMember = R.cond([
-    [hasKey('example'), parseExample(namespace, mediaType)],
+    [hasKey('example'), parseExample(context, mediaType)],
     [hasKey('examples'), R.compose(parseExamples, getValue)],
     [hasKey('schema'), R.compose(parseSchemaObjectOrRef(context), getValue)],
 

packages/openapi3-parser/test/unit/parser/oas/parseMediaTypeObject-test.js

@@ -143,6 +143,22 @@ describe('Media Type Object', () => {
         "'Media Type Object' 'example' is not supported for media type 'application/plist'"
       );
     });
+
+    it('warns for non-string example with text type', () => {
+      const mediaType = new namespace.elements.Member('text/plain', {
+        example: { message: 'Hello World' },
+      });
+
+      const parseResult = parse(context, messageBodyClass, mediaType);
+
+      expect(parseResult).to.contain.warning(
+        "'Media Type Object' 'example' should be a string for media type 'text/plain'"
+      );
+
+      const message = parseResult.get(0);
+      expect(message).to.be.instanceof(messageBodyClass);
+      expect(message.messageBody).to.be.undefined;
+    });
   });
 
   describe('#examples', () => {