NullPointerException in OpenAPIDeserializer.getHeader() after upgrading to 2.1.26

[bvo42]

Description

After upgrading from version 2.1.25 to 2.1.26, a NullPointerException occurs when parsing an OpenAPI definition. The error appears to be caused by a missing "description" field in a response header. Although "description" is optional according to the OpenAPI 3.0 specification, the parser tries to call .equals() on it unconditionally.

This issue did not occur with version 2.1.25.

Stacktrace

java.lang.NullPointerException: Cannot invoke "String.equals(Object)" because "value" is null
	at io.swagger.v3.parser.util.OpenAPIDeserializer.getHeader(OpenAPIDeserializer.java:2249)
	at io.swagger.v3.parser.util.OpenAPIDeserializer.getHeaders(OpenAPIDeserializer.java:2183)
	at io.swagger.v3.parser.util.OpenAPIDeserializer.getResponse(OpenAPIDeserializer.java:3490)
	at io.swagger.v3.parser.util.OpenAPIDeserializer.getResponses(OpenAPIDeserializer.java:3440)
	at io.swagger.v3.parser.util.OpenAPIDeserializer.getOperation(OpenAPIDeserializer.java:3586)
	at io.swagger.v3.parser.util.OpenAPIDeserializer.getPathItem(OpenAPIDeserializer.java:1060)
	at io.swagger.v3.parser.util.OpenAPIDeserializer.getPathItems(OpenAPIDeserializer.java:904)
	at io.swagger.v3.parser.util.OpenAPIDeserializer.getPaths(OpenAPIDeserializer.java:846)
	at io.swagger.v3.parser.util.OpenAPIDeserializer.parseRoot(OpenAPIDeserializer.java:378)
	at io.swagger.v3.parser.util.OpenAPIDeserializer.deserialize(OpenAPIDeserializer.java:309)
	at io.swagger.v3.parser.OpenAPIV3Parser.parseJsonNode(OpenAPIV3Parser.java:147)
	at io.swagger.v3.parser.OpenAPIV3Parser.readContents(OpenAPIV3Parser.java:178)
	at io.swagger.v3.parser.OpenAPIV3Parser.readLocation(OpenAPIV3Parser.java:97)
	at io.swagger.v3.parser.OpenAPIV3Parser.read(OpenAPIV3Parser.java:124)

Minimal Reproducible Example

Try to parse the following OpenAPI 3.0.1 JSON using swagger-parser 2.1.26:

{
  "openapi": "3.0.1",
  "info": {
    "title": "foo",
    "version": "foo"
  },
  "paths": {
    "/foo": {
      "post": {
        "responses": {
          "201": {
            "description": "Created",
            "headers": {
              "Location": {
                "required": true,
                "schema": {
                  "type": "string"
                },
                "style": "simple"
              }
            }
          }
        }
      }
    }
  }
}

Expected Behavior

The parser should handle headers without a "description" field gracefully and not throw a NullPointerException.

Workaround

Downgrading to 2.1.25 avoids the issue.

Environment

• swagger-parser version: 2.1.26
• Java version: OpenJDK 21
• OS: Ubuntu 22.04

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Thank you for your work!

[djankows]

Hey @bvo42 , thank you for reporting this.
Issue was fixed in #2166