Panic caused by using read for dynamic variables

[rupkoe]

I am trying to use an interactive script for setting dynamic variables. If read is used directly in the Taskfile, this results in a panic (see below).
If a script file containing a read statement is used instead, this also fails, but without panic (task: ... failed: exit status 1). However the culprit also seems to be the read statement, script just runs until there.

Is interactive input supported for setting dynamic variables? I was expecting so, since it does work for commands, but maybe that is just a false assumption.

• Task version: 3.3.0
• Operating System: macOS 11.2.

Taskfile

version: '3'

tasks:
  test1:
    cmds: 
      - echo {{ .dynval }}
    vars:
      dynval:
        sh: read -r; echo $REPLY

Result

$ task test1
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x1228644]

goroutine 1 [running]:
mvdan.cc/sh/v3/interp.(*Runner).readLine(0xc0001ae200, 0x1, 0x1, 0x0, 0xffffffffffffffff, 0x16718d0, 0x290)
	/home/runner/go/pkg/mod/mvdan.cc/sh/v3@v3.2.4/interp/builtin.go:676 +0x84
mvdan.cc/sh/v3/interp.(*Runner).builtinCode(0xc0001ae200, 0x13b4720, 0xc0000a0000, 0x1000100000000, 0xc0001de030, 0x4, 0xc00019a410, 0x1, 0x1, 0x0)
	/home/runner/go/pkg/mod/mvdan.cc/sh/v3@v3.2.4/interp/builtin.go:490 +0xbaa
mvdan.cc/sh/v3/interp.(*Runner).call(0xc0001ae200, 0x13b4720, 0xc0000a0000, 0x1000100000000, 0xc00019a3f0, 0x3, 0x3)
	/home/runner/go/pkg/mod/mvdan.cc/sh/v3@v3.2.4/interp/runner.go:746 +0x373
mvdan.cc/sh/v3/interp.(*Runner).cmd(0xc0001ae200, 0x13b4720, 0xc0000a0000, 0x13b31e0, 0xc0001ee000)
	/home/runner/go/pkg/mod/mvdan.cc/sh/v3@v3.2.4/interp/runner.go:345 +0x14c8
mvdan.cc/sh/v3/interp.(*Runner).stmtSync(0xc0001ae200, 0x13b4720, 0xc0000a0000, 0xc0001b7800)
	/home/runner/go/pkg/mod/mvdan.cc/sh/v3@v3.2.4/interp/runner.go:285 +0x312
mvdan.cc/sh/v3/interp.(*Runner).stmt(0xc0001ae200, 0x13b4720, 0xc0000a0000, 0xc0001b7800)
	/home/runner/go/pkg/mod/mvdan.cc/sh/v3@v3.2.4/interp/runner.go:266 +0x1e7
mvdan.cc/sh/v3/interp.(*Runner).stmts(0xc0001ae200, 0x13b4720, 0xc0000a0000, 0xc0001f0000, 0x2, 0x4)
	/home/runner/go/pkg/mod/mvdan.cc/sh/v3@v3.2.4/interp/runner.go:603 +0x57
mvdan.cc/sh/v3/interp.(*Runner).Run(0xc0001ae200, 0x13b4720, 0xc0000a0000, 0x13b0160, 0xc00018c140, 0x0, 0xc00019a360)
	/home/runner/go/pkg/mod/mvdan.cc/sh/v3@v3.2.4/interp/api.go:504 +0x2ea
github.com/go-task/task/v3/internal/execext.RunCommand(0x13b4720, 0xc0000a0000, 0xc000129370, 0x18, 0x1583520)
	/home/runner/work/task/task/internal/execext/exec.go:58 +0x352
github.com/go-task/task/v3/internal/compiler/v3.(*CompilerV3).HandleDynamicVar(0xc0000b2580, 0x0, 0x0, 0x0, 0x0, 0xc0001e2020, 0x18, 0x0, 0x0, 0x0, ...)
	/home/runner/work/task/task/internal/compiler/v3/compiler_v3.go:127 +0x26f
github.com/go-task/task/v3/internal/compiler/v3.(*CompilerV3).getVariables.func1.1(0xc0000a0a50, 0x6, 0x0, 0x0, 0x0, 0x0, 0xc0001e2020, 0x18, 0x0, 0x0, ...)
	/home/runner/work/task/task/internal/compiler/v3/compiler_v3.go:61 +0x245
github.com/go-task/task/v3/taskfile.(*Vars).Range(0xc0000aa6e0, 0xc00019a0c0, 0xc00019a0c0, 0x0)
	/home/runner/work/task/task/taskfile/var.go:68 +0x142
github.com/go-task/task/v3/internal/compiler/v3.(*CompilerV3).getVariables(0xc0000b2580, 0xc0000c4d80, 0x7ffeefbffacd, 0x5, 0x0, 0xc00009d501, 0xc0000e4100, 0xc00009d5f0, 0x1)
	/home/runner/work/task/task/internal/compiler/v3/compiler_v3.go:93 +0x2c5
github.com/go-task/task/v3/internal/compiler/v3.(*CompilerV3).GetVariables(0xc0000b2580, 0xc0000c4d80, 0x7ffeefbffacd, 0x5, 0x0, 0x1, 0x1, 0xc000129c08)
	/home/runner/work/task/task/internal/compiler/v3/compiler_v3.go:33 +0x58
github.com/go-task/task/v3.(*Executor).compiledTask(0xc0000fe000, 0x7ffeefbffacd, 0x5, 0x0, 0x100d401, 0xc00019a030, 0x30, 0x30)
	/home/runner/work/task/task/variables.go:33 +0xe4
github.com/go-task/task/v3.(*Executor).CompiledTask(...)
	/home/runner/work/task/task/variables.go:16
github.com/go-task/task/v3.(*Executor).RunTask(0xc0000fe000, 0x13b46e0, 0xc00018c040, 0x7ffeefbffacd, 0x5, 0x0, 0x0, 0x0)
	/home/runner/work/task/task/task.go:261 +0x8c
github.com/go-task/task/v3.(*Executor).Run(0xc0000fe000, 0x13b46e0, 0xc00018c000, 0xc0000aa7a0, 0x1, 0x1, 0x0, 0x0)
	/home/runner/work/task/task/task.go:96 +0x39a
main.main()
	/home/runner/work/task/task/cmd/task/task.go:187 +0xe85

[rupkoe]

Seems this could be fixed by simply adding Stdin: os.Stdin, here:

task/internal/compiler/v3/compiler_v3.go

Line 124 in fe917af

Stdout: &stdout,

This would also enable some form of interactive prompts without adding an extra feature to Task (like asked for in #236):

tasks:
  test1:
    cmds: 
      - 'echo "you just entered {{.dynval}}"'
    vars:
      dynval:
        sh: 'printf "enter: ">&2; read -r; echo $REPLY'

Could this be a viable solution?

[andreynering]

Hi @rupkoe,

Unfortunately read on variables isn't supported.

This panic was reported before at #420 and was fixed already. I tried your example and couldn't reproduce on the last release.

If you somehow can still reproduce on the most recent release, please let me know.