Proxmox ISO build fails with packer panic

[weavel]

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Overview of the Issue

So I've been following the tutorials by ChristianLempa, using his boilerplate templates for Packer on his Github. I've corrected some deprecated values pointed out by packer validate and the template passes validation.

When running an build it fails instantly with the following error:

...
Build 'ubuntu-server-jammy.proxmox-iso.ubuntu-server-jammy' errored after 9 milliseconds 581 microseconds: unexpected EOF

==> Wait completed after 9 milliseconds 581 microseconds

==> Some builds didn't complete successfully and had errors:
--> ubuntu-server-jammy.proxmox-iso.ubuntu-server-jammy: unexpected EOF

==> Builds finished but no artifacts were created.
panic: runtime error: index out of range [1] with length 1
2025/01/26 14:44:24 packer-plugin-proxmox_v1.2.2_x5.0_windows_amd64.exe plugin:
2025/01/26 14:44:24 packer-plugin-proxmox_v1.2.2_x5.0_windows_amd64.exe plugin: goroutine 9 [running]:
2025/01/26 14:44:24 packer-plugin-proxmox_v1.2.2_x5.0_windows_amd64.exe plugin: github.com/hashicorp/packer-plugin-proxmox/builder/proxmox/common.generateProxmoxDisks({0x209ea00, 0x0, 0x0?}, {0xc000132000, 0x1, 0x1?}, {0x0?, 0x0, 0x0?})
...

Other things I've checked

• Nothing is done on the proxmox side as far as I can see.
• I've verified my Proxmox API-token to be working.
• I've tried plugin version 1.2.1 also to no avail.
• I've run this on my Mac as well as on my W11 machine without any difference.
• I've searched the issue list for similar cases.

Reproduction Steps

Simply run packer build with the correct var file.

Plugin and Packer version

PS C:\Users\rikvt> packer version Packer v1.12.0

Simplified Packer Buildfile

See https://gist.github.com/weavel/28c1b130d96cd3294911047403acd821

Operating system and Environment details

• Proxmox v8.3.3
• Windows 11 24H2 with VScode 1.96.4 and Posh5 but also MacOs 15.2 on arm.

Log Fragments and crash.log files

These are all in the above mentioned gist.