x/tools/gopls: suggest testing.F if function name starts with Fuzz*

[hyangah]

$ go version -m ~/go/bin/gopls
/Users/hakim/go/bin/gopls: devel go1.17-3fa42437b5 Wed Jun 23 16:05:25 2021 +0000
        path    golang.org/x/tools/gopls
        mod     golang.org/x/tools/gopls        v0.7.0  h1:JQBHW81Gsyim6iDjUwGoPeSpXrSqwen3isPJLfDfaYU=
        dep     github.com/BurntSushi/toml      v0.3.1  h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
        dep     github.com/google/go-cmp        v0.5.5  h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
        dep     github.com/sergi/go-diff        v1.1.0  h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0=
        dep     golang.org/x/mod        v0.4.2  h1:Gz96sIWK3OalVv/I/qNygP42zyoKp3xptRVCWRFEBvo=
        dep     golang.org/x/sync       v0.0.0-20210220032951-036812b2e83c      h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
        dep     golang.org/x/sys        v0.0.0-20210510120138-977fb7262007      h1:gG67DSER+11cZvqIMb8S8bt0vZtiN6xWYARwirrOSfE=
        dep     golang.org/x/tools      v0.1.3-0.20210608163600-9ed039809d4c    h1:Pv9gNyJFYVdpUAVZYJ1BDSU4eGgXQ+0f3DIGAdolO5s=
        dep     golang.org/x/xerrors    v0.0.0-20200804184101-5ec99f83aff1      h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
        dep     honnef.co/go/tools      v0.2.0  h1:ws8AfbgTX3oIczLPNPCu5166oBg9ST2vNs0rcht+mDE=
        dep     mvdan.cc/gofumpt        v0.1.1  h1:bi/1aS/5W00E2ny5q65w9SnKpWEF/UIOqDYBILpo9rA=
        dep     mvdan.cc/xurls/v2       v2.2.0  h1:NSZPykBXJFCetGZykLAxaL6SIpvbVy/UFEniIfHAa8A=

[danishprakash]

Would like to work on this cc/ @hyangah

[hyangah]

And I wonder if gopls can handle autocomplete specially for f.Fuzz since its function signature itself is not very informative, but it is meant to take only function type arg of a special form. And analyzer on this param would be nice. @findleyr do you want to keep track of this as a separate feature request?

cc @katiehockman

[findleyr]

And analyzer on this param would be nice. @findleyr do you want to keep track of this as a separate feature request?

That is a very good idea, and easy to implement! Please open a separate issue, in gopls/on-deck. It can be help-wanted too as this should be straightforward to add.

[danishprakash]

I completely forgot about this issue, will work on this over the weekend, thanks for the ping :)

[danishprakash]

Sorry for the huge delay on this.

@hyangah while looking into this, I realized we don't show/order completions based on the function name, please correct me If I'm wrong here.

Based on the above, I tried a very brittle implementation which essentially compares the enclosing function with all the shortlisted candidates and orders them accordingly. The output looks something like this:

Bench*	Fuzz*

It does the same for Test* too but again, the heuristic is relatively straightforward. I can polish this up and raise a CL for the team to review for further discussion.

danishprakash/tools@bc8097d

cc: @findleyr

[pjweinb]

I'm unclear on what's being requested/proposed in this issue. In a test file, after the '.', there's only one legal completion in
'TestFoo(t *testing.)', 'TestMain(t *testing.)', 'BenchmarkFoo(t *testing.', or 'FuzzFoo(t *testing.'. So the top gopls suggestion then should be 'T', or 'M', or 'B' or 'F'. This seems doable, but doesn't save the user much.

Best would be to offer to complete the whole signature after the user types the '(', but gopls does not generate completions when it sees '('.

Intermediate would be to offer ' *testing.T' when the user types the formal parameter in 'func TestFoo(t' (and ' *testing.F' for 'FuzzFoo(f' etc).

[hyangah]

Throughout typing, I've never seen testing.F suggested as top candidates. Ideally, it would be nice if testing.F was presented as soon as I start typing inside () or after t *. (gopls v0.8.0-pre.1 with go1.18beta2)

Finally -

As @danishprakash found out, there is no specialization for test/bench functions either so same problem exists for testing.T. testing.B may be just lucky one because it's one of the first candidates in alphabetical order.

[gopherbot]

Change https://go.dev/cl/385974 mentions this issue: internal/lsp: Provide completions for test function definitions

[zikaeroh]

I would definitely like to see this completion list prioritized to put the "right" struct type at the top; I suggested using snippet completion on above CL (to complete the full signature with an empty placeholder or something), but for those that don't use snippet completions, the sorting would be a marked improvement. For me, it's definitely more useful than "doesn't save the user much" would imply.