[BUG][JAVA][SPRING] Nullaways warn with JSpecify

[pkernevez]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

With Java & spring generator, when using JSpecify Nullable annotation, the generated code don't add a @Nullable on the parameter of the generated method toIndentedString.
That creates a warns with nullAway because this private methode is called with parameters that could be nullable.

openapi-generator version

7.18.2, this is not a regression

OpenAPI declaration file content or url

My Maven plugin conf:

                    <configuration>
                        <generatorName>spring</generatorName>
...
                        <importMappings>
                            <importMapping>Nullable=org.jspecify.annotations.Nullable</importMapping>
                        </importMappings>
                    </configuration>

Generation Details

Generated POJO:

package ...

import org.jspecify.annotations.Nullable;
...
@Generated(value = "org.openapitools.codegen.languages.SpringCodegen", date = "2025-12-30T12:03:39.667194+01:00[Europe/Zurich]", comments = "Generator version: 7.18.0")
public class XxxDto {

      private @Nullable String myVar;
....
            @Override
            public String toString() {
              StringBuilder sb = new StringBuilder();
              sb.append("class XxxDto {\n");
              sb.append("    myVar: ").append(toIndentedString(myVar)).append("\n"); /* <=== Clash here as myVar is nullable*/
              sb.append("}");
              return sb.toString();
            }

            /**
            * Convert the given object to string with each line indented by 4 spaces
            * (except the first line).
            */
            private String toIndentedString(Object o) {  /* <=== Clash here because o is not Nullable */
            if (o == null) {
            return "null";
            }
            return o.toString().replace("\n", "\n    ");
            }

Expected POJO

package ...

import org.jspecify.annotations.Nullable;
...
@Generated(value = "org.openapitools.codegen.languages.SpringCodegen", date = "2025-12-30T12:03:39.667194+01:00[Europe/Zurich]", comments = "Generator version: 7.18.0")
public class XxxDto {

      private @Nullable String myVar;
....
            @Override
            public String toString() {
              StringBuilder sb = new StringBuilder();
              sb.append("class XxxDto {\n");
              sb.append("    myVar: ").append(toIndentedString(myVar)).append("\n"); 
              sb.append("}");
              return sb.toString();
            }

            /**
            * Convert the given object to string with each line indented by 4 spaces
            * (except the first line).
            */
            private String toIndentedString(@Nullable Object o) {  /* <== only add @Nullable */
            if (o == null) {
            return "null";
            }
            return o.toString().replace("\n", "\n    ");
            }

Steps to reproduce

Setup JSpecify and NullAway.
Run the generator, when compiling the following Warns are generated:

[INFO] -------------------------------------------------------------
[WARNING] COMPILATION WARNING : 
[INFO] -------------------------------------------------------------
[WARNING] .../shared/target/generated-sources/src/main/java/tech/generated/dto/AboutReadDto.java:[154,57] [NullAway] passing @Nullable parameter 'tenantId' where @NonNull is required
    (see http://t.uber.com/nullaway )

Related issues/PRs

I was using the mechanism introduce in this PR: #21498

Suggest a fix

See the associated PR.