Manifest.from(Object...) does not support merging Manifest implementations

[bjhargrave]

Expected Behavior

One should be able to pass an implementation of org.gradle.api.java.archives.Manifest to Manifest.from(Object...) to get the argument manifest merged into the receiver manifest.

The javadoc indicates this is supported.

Current Behavior

The current implementation of DefaultManifestMergeSpec requires the manifest object to be an instance of the internal DefaultManifest type:

gradle/subprojects/platform-jvm/src/main/java/org/gradle/api/java/archives/internal/DefaultManifestMergeSpec.java

Line 152 in 270f942

if (mergePath instanceof DefaultManifest) {

rather than the Manifest type. When the manifest object is not an instance of the internal DefaultManifest type, the code attempts to resolve the manifest object as a file path which fails.

Context

The is affecting the use of custom manifest object in plugins as they cannot merge a manifest object unless it is of the internal DefaultManifest type.

Steps to Reproduce

This can be seen when using the latest fix bndtools/bnd#5276 to the Bnd Gradle plugin (6.4.0-SNAPSHOT) when building JUnit 5 which also uses the com.github.johnrengelman.shadow plugin. These two plugins interact over the jar task's manifest object. With the Bnd fix, the following exception occurs.

Caused by: org.gradle.internal.typeconversion.UnsupportedNotationException: Cannot convert the provided notation to a File or URI: org.gradle.api.java.archives.internal.DefaultManifest@1ab3a446.
The following types/formats are supported:
  - A String or CharSequence path, for example 'src/main/java' or '/usr/include'.
  - A String or CharSequence URI, for example 'file:/usr/include'.
  - A File instance.
  - A Path instance.
  - A Directory instance.
  - A RegularFile instance.
  - A URI or URL instance.
  - A TextResource instance.
        at org.gradle.internal.typeconversion.ErrorHandlingNotationParser.parseNotation(ErrorHandlingNotationParser.java:57)
        at org.gradle.api.internal.file.AbstractFileResolver.convertObjectToFile(AbstractFileResolver.java:105)
        at org.gradle.api.internal.file.AbstractBaseDirFileResolver.doResolve(AbstractBaseDirFileResolver.java:63)
        at org.gradle.api.internal.file.AbstractFileResolver.resolve(AbstractFileResolver.java:74)
        at org.gradle.api.internal.file.AbstractFileResolver.resolve(AbstractFileResolver.java:48)
        at org.gradle.api.java.archives.internal.DefaultManifest.read(DefaultManifest.java:281)
        at org.gradle.api.java.archives.internal.DefaultManifest.<init>(DefaultManifest.java:77)
        at org.gradle.api.java.archives.internal.DefaultManifestMergeSpec.createManifest(DefaultManifestMergeSpec.java:155)
        at org.gradle.api.java.archives.internal.DefaultManifestMergeSpec.merge(DefaultManifestMergeSpec.java:84)
        at org.gradle.api.java.archives.internal.DefaultManifestMergeSpec$merge.call(Unknown Source)
        at com.github.jengelman.gradle.plugins.shadow.tasks.DefaultInheritManifest$_getEffectiveManifest_closure1.doCall(DefaultInheritManifest.groovy:65)

I have a PR I will submit with the fix for this issue.

Your Environment

Build scan URL:
https://scans.gradle.com/s/huhyrwmnaz73w