Fix testonly attribute handling

[meteorcloudy]

Fix the following error when using test_only in Bzlmod

ERROR: Traceback (most recent call last):
	File "/private/var/tmp/_bazel_pcloudy/829441223e9fec5a5a2e3d1dd743fdf0/external/rules_jvm_external~5.2/private/extensions/maven.bzl", line 304, column 52, in _maven_impl
		artifacts_json = [_json.write_artifact_spec(a) for a in artifacts]
	File "/private/var/tmp/_bazel_pcloudy/829441223e9fec5a5a2e3d1dd743fdf0/external/rules_jvm_external~5.2/specs.bzl", line 230, column 38, in _artifact_spec_to_json
		"\", \"version\": \"" + artifact_spec["version"] + "\""
Error: unsupported binary operation: string + bool

[meteorcloudy]

Is there any way we can improve the quality of Bzlmod support and have more test coverage perhaps?

[meteorcloudy]

Also I noticed "fetch_sources": attr.bool(default = True), in Bzlmod: https://github.com/bazelbuild/rules_jvm_external/blob/5.2/private/extensions/maven.bzl#L41

And eventually it's an OR of all maven installs. Is there any reason for this attribute to be True by default in Bzlmod?

[shs96c]

Ooops. Nice catch. Thank you! LGTM

[shs96c]

We set the default to be True because the common case is for people to use an IDE for working on their code, and having the sources available makes that experience significantly nicer. We can change it to False if necessary, and it's probably best if we take the value from the root module only.

[meteorcloudy]

We can change it to False if necessary, and it's probably best if we take the value from the root module only.

Agree, in fact, currently it's not possible for the root module to turn this off if another dependency is using maven install without overriding it to False.