code review 10336044: go.tools/cmd/vet: check for missing printf verb

go.tools/cmd/vet: check for missing printf verb
A trailing % resulted in a bad error message.
Also clean up a couple of dregs left over from the
refactoring to add indexed formats.

[r, 2013-06-17 18:17:21]

Hello dsymonds (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go.tools

[dsymonds, 2013-06-17 23:46:27]

https://codereview.appspot.com/10336044/diff/1/cmd/vet/testdata/print.go
File cmd/vet/testdata/print.go (right):

https://codereview.appspot.com/10336044/diff/1/cmd/vet/testdata/print.go#newc...
cmd/vet/testdata/print.go:128: fmt.Sprintf("%[3]d", 2)       // ERROR "wrong
number of args for format in Sprintf call"
this one looks wrong. there's a single format specifier, and a single argument,
so the number of args is correct. It is that the argument number is out of
range. I guess you could claim that the "3" is correct and so there's the wrong
number of arguments to support it, but I think that's backwards from what most
people would expect.

[r, 2013-06-18 00:38:44]

https://codereview.appspot.com/10336044/diff/1/cmd/vet/testdata/print.go
File cmd/vet/testdata/print.go (right):

https://codereview.appspot.com/10336044/diff/1/cmd/vet/testdata/print.go#newc...
cmd/vet/testdata/print.go:128: fmt.Sprintf("%[3]d", 2)       // ERROR "wrong
number of args for format in Sprintf call"
you're right, it's bad wording.

[r, 2013-06-18 00:38:48]

Hello dsymonds@golang.org (cc: golang-dev@googlegroups.com),

Please take another look.

[dsymonds, 2013-06-18 02:23:45]

sorry, I realise this is a bit like nailing jelly to a wall.

https://codereview.appspot.com/10336044/diff/5001/cmd/vet/testdata/print.go
File cmd/vet/testdata/print.go (right):

https://codereview.appspot.com/10336044/diff/5001/cmd/vet/testdata/print.go#n...
cmd/vet/testdata/print.go:121: Printf(format, "hi") // ERROR "Printf accesses
argument number 2 after format for verb %s; 1 present"
I think this is a regression; shouldn't this still be "wrong number of args"? I
think this "... accesses argument number ..." error should only occur for
%[2]d-style printf argument indexes.

[r, 2013-06-18 03:57:41]

Printf("%s %s", 2)

it could be "wrong number of args". i was trying to be helpful. it
*is* trying to access an extra argument.

[dsymonds, 2013-06-18 03:59:40]

On 18 June 2013 13:57, Rob Pike <r@golang.org> wrote:

> Printf("%s %s", 2)
>
> it could be "wrong number of args". i was trying to be helpful. it
> *is* trying to access an extra argument.

Yeah, but I think the most common way someone is going to trip over
that is that they forget to write an argument. The "accessing an extra
argument" terminology is also a bit obscure.

[r, 2013-06-18 06:05:05]

Hello dsymonds@golang.org (cc: golang-dev@googlegroups.com),

Please take another look.

[dsymonds, 2013-06-18 06:22:44]

LGTM

[r, 2013-06-18 15:21:11]

*** Submitted as
https://code.google.com/p/go/source/detail?r=e3e3e4be74ef&repo=tools ***

go.tools/cmd/vet: check for missing printf verb
A trailing % resulted in a bad error message.
Also clean up a couple of dregs left over from the
refactoring to add indexed formats.

R=dsymonds
CC=golang-dev
https://codereview.appspot.com/10336044

[dsymonds, 2013-06-20 04:09:30]

This latest code is still producing extra output. For a line of code such as
  t.Errorf("Foo(%v) = %s, want bar")
I get these three vet errors:
  argument number 1 for verb %v out of range
  argument number 2 for verb %s out of range
  wrong number of args for format in Errorf call: 2 needed but 0 args

Only the last one should be printed.

[r, 2013-06-20 17:30:41]

I can't reproduce this. At tip, I see only one message:

testdata/print.go:160: missing argument for Errorf verb %v: need 1, only have 0

The 'only' is silly and I'll delete that word on the next refresh.