In dynamic (shell) variables, template expansion resulting in an empty (no characters) script block causes type error when referenced

[WinkelCode]

Sample taskfile showcasing the bug:

version: '3'

vars:
  ITEMS:
    - "a"
    - "b"

tasks:
  default:
    vars:
      FILTERED_STR:
        sh: |-
          {{range .ITEMS -}}
          {{if eq . "c" -}}
          echo {{.}}
          {{end -}}
          {{end -}}
      FILTERED:
        ref: compact (splitList "\n" .FILTERED_STR)
    cmds:
      - echo "{{.FILTERED}}"

Explanation

When a sh: block becomes completely empty after template expansion and its value is referenced later, Task throws a type error instead of treating it as an empty string.

$ task
template: resolver:1:26: executing "resolver" at <.FILTERED_STR>: wrong type for value; expected string; got interface {}

Workaround

The workaround is to ensure any character always remains in the script block. For instance, a # could be added, or whitespace trimming - }} could be omited.

[...]
      FILTERED_STR:
        sh: |-
          #
          {{range .ITEMS -}}
          {{if eq . "c" -}}
          echo {{.}}
          {{end -}}
          {{end -}}
[...]

$ task
task: [default] echo "[]"
[]

---

• Task version:

$ task --version
Task version: 3.39.2 ()

• Operating system: macOS Sequoia 15.1
• Experiments enabled: None

[pd93]

Thanks for the detailed repro. #1904 should fix this.