proposal: cmd/go: add transitive Deps for TestImports and XTestImports

[jehiah]

go list provides a .Deps which has the recursive list of dependencies for .Imports. This is important because it provides the complete list of dependencies that must be fulfilled to run go build

Unfortunately there is no recursive dependency provided for TestImports or XTestImports. Those have a dependency tree that needs to be fulfilled in order to go test but it's non-trivial to retrieve that dependency list. (especially when trying to filter out stdlib entries)

Currently

// Dependency information
Imports      []string // import paths used by this package
Deps         []string // all (recursively) imported dependencies
TestImports  []string // imports from TestGoFiles
XTestImports []string // imports from XTestGoFiles

What's expected?

// Dependency information
Imports      []string // import paths used by this package
Deps         []string // all (recursively) imported dependencies
TestImports  []string // imports from TestGoFiles
TestDeps     []string // all (recursively) imported dependencies from TestGoFiles
XTestImports []string // imports from XTestGoFiles
XTestDeps    []string // all (recursively) imported dependencies from XTestGoFiles

This would allow a command like the following to output the complete set of dependencies needed to run go build or go test.

go list -f '{{join .Deps "\n"}}{{if len .TestDeps}}{{"\n"}}{{end}}{{join .TestDeps "\n"}}{{if len .XTestDeps}}{{"\n"}}{{end}}{{join .XTestDeps "\n"}}' | sort | uniq

Currently you have to run go list '{{join .Deps "\n"}}' $import_path on each import path from .TestImports and .XTestImports.

[mvdan]

How about one single .TestDeps, holding .Deps plus all the transitive test dependencies?

That would mirror what the get command has. For example, .Deps is the same that it uses in go get, while .TestDeps would be the same that it uses in go get -t.

[jehiah]

@mvdan that seems reasonable and targets my use case equally well.

[mvdan]

Happy to give it a go if others agree on the design.

[mvdan]

Also, I'm thinking now that it probably requires a better name, if we are to mirror go get -t. TestDeps seems to mean "only the test dependencies", not "all dependencies including the test ones".

Perhaps DepsWithTest or DepsInclTest. Or perhaps we should make TestDeps be the transitive test dependencies only, and it's up to the user to use both Deps and TestDeps if required (or merge the lists, somehow).

[stapelberg]

The discussed change would be valuable for Debian as well, where we currently query {{ .Deps }}, and entirely miss dependencies which are only used for testing.

Edit: it was pointed out to me that in the particular use-case (generating the Built-Using field), excluding testing deps is actually correct, so nevermind :).

[mvdan]

I'm repurposing this as a proposal, in the hopes that a decision will be made on it while the Go 1.11 tree is open. The proposed change isn't trivial either, so it makes sense to have a proposal.

[jehiah]

Thanks @mvdan. Let me know if i can be of any assistance with context related to my use.

[rsc]

We will need to address this more generally for the new go/loader package. I think this can wait until after that's done - it will probably just fall out naturally.