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fix: dereference header before normalizing#22613

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fix: dereference header before normalizing#22613
adrianhj wants to merge 1 commit intoOpenAPITools:masterfrom
adrianhj:master

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@adrianhj adrianhj commented Jan 2, 2026 •
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Fixes null pointer issue within #22576.

Without fix applied:

$ java -Dlog.level=warn -jar openapi-generator-cli.jar generate -i containers_4.yaml -g spring -o generated
[main] ERROR o.o.codegen.DefaultGenerator - An exception occurred in OpenAPI Normalizer. Please report the issue via https://github.com/openapitools/openapi-generator/issues/new/:
[main] ERROR o.o.codegen.DefaultGenerator - An exception occurred in OpenAPI Normalizer. Please report the issue via https://github.com/openapitools/openapi-generator/issues/new/:
java.lang.NullPointerException: Cannot invoke "io.swagger.v3.oas.models.media.Schema.get$ref()" because "schema" is null
	at org.openapitools.codegen.OpenAPINormalizer.normalizeSchema(OpenAPINormalizer.java:699)
	at org.openapitools.codegen.OpenAPINormalizer.normalizeHeaders(OpenAPINormalizer.java:561)
	at org.openapitools.codegen.OpenAPINormalizer.normalizeResponse(OpenAPINormalizer.java:545)
	at org.openapitools.codegen.OpenAPINormalizer.normalizeResponses(OpenAPINormalizer.java:533)
	at org.openapitools.codegen.OpenAPINormalizer.normalizePaths(OpenAPINormalizer.java:426)
	at org.openapitools.codegen.OpenAPINormalizer.normalize(OpenAPINormalizer.java:355)
	at org.openapitools.codegen.DefaultGenerator.configureGeneratorProperties(DefaultGenerator.java:266)
	at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:1277)
	at org.openapitools.codegen.cmd.Generate.execute(Generate.java:535)
	at org.openapitools.codegen.cmd.OpenApiGeneratorCommand.run(OpenApiGeneratorCommand.java:32)
	at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:66)
[main] WARN  o.o.codegen.utils.ExamplesUtils - No application/json content media type found in response. Response examples can currently only be generated for application/json media type.
############################################################################################
# Thanks for using OpenAPI Generator.                                                      #
# We appreciate your support! Please consider donation to help us maintain this project.   #
# https://opencollective.com/openapi_generator/donate                                      #
############################################################################################

With fix applied:

$ java -Dlog.level=warn -jar openapi-generator-cli.jar generate -i containers_4.yaml -g spring -o generated
[main] WARN  o.o.codegen.utils.ExamplesUtils - No application/json content media type found in response. Response examples can currently only be generated for application/json media type.
############################################################################################
# Thanks for using OpenAPI Generator.                                                      #
# We appreciate your support! Please consider donation to help us maintain this project.   #
# https://opencollective.com/openapi_generator/donate                                      #
############################################################################################

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Summary by cubic

Dereference header references before normalizing to prevent a NullPointerException when a header schema is missing. Fixes #22576 and stops generator crashes for OAS 3.1 specs with $ref headers.

  • Bug Fixes
    • In normalizeHeaders, dereference headers with $ref and normalize only when schema exists.
    • Added a unit test and 3.1 spec fixture to confirm normalization runs without exceptions.

Written for commit 149eca2. Summary will update on new commits.

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No issues found across 3 files

@adrianhj adrianhj mentioned this pull request Jan 2, 2026
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adrianhj commented Jan 5, 2026

@wing328 FYI

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wing328 commented Jan 5, 2026

thanks for the PR

will get it reviewed and merged soon later this week

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wing328 commented Jan 11, 2026

UPDATE: I've merged #22671 instead (better null check and sample update to catch the issue moving forward).

Please give it a try with the latest master: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-to-test-with-the-latest-master-of-openapi-generator

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wing328 commented Jan 12, 2026

FYI. I just merged #22672 to normalize headers in components as well.

Closing this one for now. Happy to reopen if needed.

Thanks again for contributing a fix

@wing328 wing328 closed this Jan 12, 2026
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java.lang.NullPointerException: Cannot invoke "io.swagger.v3.oas.models.media.Schema.get$ref()" because "schema" is null

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