[REQ] Generated date should be reproducible (or disabled by default)

[bdemers]

Is your feature request related to a problem? Please describe.

To meet the requirements of Reproducible Builds, generated timestamps should be predicable (so that packages can be rebuild with the same source and produce the same output)

Describe the solution you'd like

For projects using the Maven plugin, this could mean that the generatedDate would be set to Maven's project.build.outputTimestamp property.

openapi-generator/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java

Line 289 in 6da343a

config.additionalProperties().put("generatedDate", ZonedDateTime.now().toString());

Gradle's approach to this is to use a fixed date:
https://github.com/gradle/gradle/blob/f4fcd0b4f2c6a1903f80a4299a540d73d722f127/platforms/core-runtime/files/src/main/java/org/gradle/api/internal/file/archive/ZipEntryConstants.java#L24-L39

Describe alternatives you've considered

Alternatively configOptions.hideGenerationTimestamp could be set to true by default.

Another alternative would be to use the timestamp of the openapi spec file. There are a lot of edge cases around this, the file could be downloaded and timestamp not preserved, file could be copied at build time (and timestamp not preserved). Additionally, other inputs to the generator could change resulting in different code using the same source spec. So this probably isn't a valid option.

Additional context

See:

• Maven Artifact Plugin (list of non-compliant and fixed plugin versions)
• Maven Reproducible Builds Guide
• Maven Reproducible Builds wiki page

[bdemers]

Current workaround, set configOptions.hideGenerationTimestamp to true

[hboutemy]

if the plugin was using the standard project.build.outputTimestamp value to detect if Reproducible Builds is activated, there would not even be any manual parameter to configure
= what is promoted in Maven

[clayburn]

In Gradle builds, this dynamic timestamp causes cache misses, leading to degraded build performance. In working with users, we find that most users do not even realize the timestamps are there, so they are getting no value from them, but the default inadvertently slows down their build.