Packer: 1.6.0 interprets 'null' user variables as errors with -syntax-only flag

[miketimofeev]

Overview of the Issue

We have a bunch of templates where some required user variables are declared as 'null' as described in the docs.

"variables": {
        "vcenter_server": null,
        "vcenter_username": null,
        "vcenter_password": null,
        "vcenter_datacenter": null,

Starting from version 1.6.0 packer validate -syntax-only command fails with

Error initializing core: 4 errors occurred:
        * required variable not set: vcenter_password
        * required variable not set: vcenter_username
        * required variable not set: vcenter_server
        * required variable not set: vcenter_datacenter

Versions 1.5.6 and below work fine.

Reproduction Steps

Run packer validate -syntax-only <template_path> against template with 'null' user variables

Packer version

1.6.0

Simplified Packer Buildfile

Example in the description

Operating system and Environment details

Happens both on macOS and windows

Log Fragments and crash.log files

Validation log provided in the description

[nywilken]

Thanks for reaching out! This issue is due to the build command parsing logic that is now used by the validation command. We'll work on getting this fixed for the next release.

[hashibot[bot]]

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