fix(ProtoBuf,XML): component data repeatable

[jkowalleck]

fixes #518

[jkowalleck]

@nscuro , could I ask you for a review?

would you consider the proposed changes as non-breaking?
I got the impression this would be a non-breaking based on this: #518 (comment)

Despite bufbuild/buf:1.30.1 thinks this would be a breaking change ...

[nscuro]

@jkowalleck You are using the config category FILE for buf's breaking change detection:

specification/tools/src/test/proto/buf_breaking-version.yaml

Lines 3 to 7 in 19a1530

	version: v1
	breaking: # https://buf.build/docs/configuration/v1/buf-yaml#breaking
	use: # see https://buf.build/docs/breaking/overview#rules-and-categories
	- FILE
	- WIRE_JSON

The docs define FILE as:

Detects generated source code breakage on a per-file basis

So, while the proposed change is compatible WRT the wire format, source code generated from the schema will break. For example in Java, optional ComponentData data would be accessible as:

// Returns ComponentData
component.getData()

whereas repeated ComponentData data would be:

// Returns List<ComponentData>
component.getDataList()

Similarly, construction of Proto objects will be different, too.

It's safe to assume that almost all language bindings will mirror this behavior.

IMO this is fine. I think the spec should focus on wire compatibility.

[jkowalleck]

thank you so much, @nscuro.

I am not very experienced with ProtoBuf, so I might have configured the checks unideal.

IMO this is fine. I think the spec should focus on wire compatibility.

This sounds plausible.
Would you say it is safe to change the breaking detection to use "wire" only, by dropping "file"?
If so, I will change the applied configs via #532

[stevespringett]

LGTM