Can't use computed lists in matrix loops

[mjpieters]

Description

You can only use literal lists in matrix loops, either by reference, or directly. Using a list created from some other source, fails.

See the example taskfile, where OS_KEYS is a list produced by the keys template command.

Output for task:

[spew] OS_VAR: ([]interface {}) (len=3 cap=3) {
[spew]  (string) (len=7) "windows",
[spew]  (string) (len=5) "linux",
[spew]  (string) (len=6) "darwin"
[spew] }
[spew] OS_KEYS: ([]string) (len=3 cap=4) {
[spew]  (string) (len=6) "darwin",
[spew]  (string) (len=7) "windows",
[spew]  (string) (len=5) "linux"
[spew] }
[list-ref] windows/amd64
[list-ref] windows/arm64
[list-ref] linux/amd64
[list-ref] linux/arm64
[list-ref] darwin/amd64
[list-ref] darwin/arm64
task: Failed to run task "default": task: Failed to parse /tmp/repro/Taskfile.yml:
matrix reference ".OS_KEYS" must resolve to a list

I do note that spew shows that the keys list a []string array, while OS_VAR is a []interface {} array, but I wouldn't expect that to be the issue.

Version

3.45.5

Operating system

macos 15.6.1

Experiments Enabled

No response

Example Taskfile

version: '3'
output: prefixed

vars:
  OS_MAP:
    map:
      windows: "Microsoft Windows"
      linux: "Linux kernel"
      darwin: "Apple macos"
  OS_VAR: ["windows", "linux", "darwin"]
  OS_KEYS: { ref: keys .OS_MAP }
  ARCH_VAR: ["amd64", "arm64"]
  
tasks:
  spew:
    silent: true
    cmds:
      - "echo -n 'OS_VAR: {{spew .OS_VAR}}'"
      - "echo -n 'OS_KEYS: {{spew .OS_KEYS}}'"
  list-ref:
    silent: true
    cmds:
      - for:
          matrix:
            OS: { ref: .OS_VAR }
            ARCH: { ref: .ARCH_VAR }
        cmd: echo "{{.ITEM.OS}}/{{.ITEM.ARCH}}"
  keys-output:
    silent: true
    cmds:
      - for:
          matrix:
            OS: { ref: .OS_KEYS }
            ARCH: { ref: .ARCH_VAR }
        cmd: echo "{{.ITEM.OS}}/{{.ITEM.ARCH}}"
  default:
    cmds:
      - task: spew
      - task: list-ref
      - task: keys-output

[trulede]

Yeah, the type switch matches on []any but you have a []string and so it does not match.

task/variables.go

Line 419 in 2161f33

case []any:

The solution might be to use reflection:

v := reflect.ValueOf(x)
switch v.Kind() {
case reflect.Slice:
...

[no-hup]

Ran into this too — the matrix ref path only accepts a literal []any, so anything computed via template functions like splitList (which resolve to []string) gets rejected even though it's a perfectly good list. I've got a small fix ready (type-switch mirroring what itemsFromFor already accepts) plus tests; opening a PR shortly.