Make it possible for the output from the BuildInfo task to be repeatable

[sdavids]

Follow-up to #8391

The build-info.properties file contains a timestamp in the header comment, this leads to non-reproducible builds.

https://docs.spring.io/spring-boot/docs/2.0.5.RELEASE/gradle-plugin/reference/html/#integrating-with-actuator-build-info

springBoot {
  buildInfo {
    properties {
      time = null
    }
  }
}

Will remove the build.time property, but the timestamp in the header comment will be changed on every build:

#Properties
#Mon Sep 17 17:34:11 CEST 2018
build.artifact=example-artifact
build.group=example-group
build.name=example-name
build.version=1.0.0

[wilkinsona]

Thanks for the report. Nulling out the time is aimed at up-to-date checking rather than repeatability. It works fine for up-to-date checks as Gradle compares the property key-value pairs and doesn't care about any comments. Unfortunately, the writing of the date is baked into java.util.Properties and can't be disabled. Short of implementing our own class for writing the properties to disk, or using a custom Writer that suppresses the output of the comment, there's not a lot we can do about this.

[sdavids]

Also, the order of the keys could be sorted to be independent of their hash values.

[sdavids]

https://docs.gradle.org/current/dsl/org.gradle.api.tasks.WriteProperties.html

• no timestamp comment is generated at the beginning of the file
• the lines in the resulting files are separated by a pre-set separator (defaults to '\n') instead of the system default line separator
• the properties are sorted alphabetically

[wilkinsona]

Thanks for the pointer to WriteProperties. I wasn't aware of that Gradle task. Unfortunately, the code in question here is shared between our Gradle plugin and our Maven plugin so changing it to depend on something that's Gradle-specific isn't an option. It does, however, open up the option of reworking things to no longer use the shared code and use WriteProperties in the Gradle case. We've done something similar in other places in the plugin where the shared code didn't work well with Gradle.

[pgilad]

This is what I do in the meantime:

springBoot {
    mainClassName = 'com.sample.sample.SampleApplication'
    buildInfo {
        properties {
             time = null
        }

        // Watch https://github.com/spring-projects/spring-boot/issues/14494
        doLast {
            File f = new File(destinationDir, 'build-info.properties')
            f.text = f.filterLine { !it.startsWith('#') }
        }
    }
}

And I get the same md5 for each jar