## Description
**Steps to reproduce:**
# Navigate to https://wikifunctions.beta.wmflabs.org/wiki/Special:CreateZObject?zid=Z14&Z14K1=Z801 to create a new Implementation for Z801/Echo
# Select 'Code' for Implementation type and 'JavaScript' for Language
# [Observe contents of Code block]
# Change function to Z802/If
# [Observe contents of Code block]
# Switch Implementation type to 'Composition' and back to 'Code'
# [Observe contents of Code block]
**Observed behavior:**
* Initial code block is pre-filled with `function Z801( ) { … }` – doesn't add the input (`Z801K1`)
* Code block isn't updated when target function is changed – still for Z801
* Re-created code block is correct after switching back from Composition to Code: `function Z802( Z802K1, Z802K2, Z802K3 ) { … }`
**Expected behavior (Acceptance criteria):**
* Initial code block should be `function Z801( Z801K1 ) { … }`
* On changing function, the code block should be updated to `function Z802( Z802K1, Z802K2, Z802K3 ) { … }`
# Switch Implementation type to 'Composition' and back to 'Code' should not create a difference.
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## Completion checklist
* [ ] Before closing this task, review one by one the checklist available here: https://www.mediawiki.org/wiki/Abstract_Wikipedia_team/Definition_of_Done#Front-end_Task/Bug_Completion_Checklist