packer crash

[hanwen-flow]

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Overview of the Issue

packer crash, after removing some sections from a working hcl file.

Reproduction Steps

unfortunately, I lost the repro while trying to reduce the input file.

Packer version

$ packer version
Packer v1.12.0

Simplified Packer Template

Operating system and Environment details

ubuntu 24.04

Log Fragments and crash.log files

$ cat crash.log~
2025/02/10 10:26:28 [INFO] Packer version: 1.12.0 [go1.22.9 linux amd64]
2025/02/10 10:26:28 [INFO] PACKER_CONFIG env var not set; checking the default config file path
2025/02/10 10:26:28 [INFO] PACKER_CONFIG env var set; attempting to open config file: /home/hanwen/.packerconfig
2025/02/10 10:26:28 [WARN] Config file doesn't exist: /home/hanwen/.packerconfig
2025/02/10 10:26:28 [INFO] Setting cache directory: /home/hanwen/.cache/packer
2025/02/10 10:26:28 [TRACE] listing potential installations for <nil> that match "". plugingetter.ListInstallationsOptions{PluginDirectory:"/home/hanwen/.config/packer/plugins", BinaryInstallationOptions:plugingetter.BinaryInstallationOptions{APIVersionMajor:"5", APIVersionMinor:"0", OS:"linux", ARCH:"amd64", Ext:"", Checksummers:[]plugingetter.Checksummer{plugingetter.Checksummer{Type:"sha256", Hash:(*sha256.digest)(0xc0004e4080)}}, ReleasesOnly:false}}
2025/02/10 10:26:28 [INFO] found external [chroot ebs ebssurrogate ebsvolume instance] builders from amazon plugin
2025/02/10 10:26:28 [INFO] found external [import] post-processors from amazon plugin
2025/02/10 10:26:28 found external [ami parameterstore secretsmanager] datasource from amazon plugin
2025/02/10 10:26:28 plugin "/home/hanwen/.config/packer/plugins/github.com/hashicorp/amazon/packer-plugin-amazon_v1.3.4_x5.0_linux_amd64" does not support Protobuf, forcing use of Gob
2025/02/10 10:26:28 [INFO] found external [-packer-default-plugin-name-] builders from docker plugin
2025/02/10 10:26:28 [INFO] found external [import push save tag] post-processors from docker plugin
2025/02/10 10:26:28 [TRACE] validateValue: not active for gcp_base_image_windows_2022_x86_64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for prerelease, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_debian12_arm64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_ubuntu2404_arm64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for version, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_customers, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for gcp_builder_project, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_windows_2022_x86_64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for gcp_builder_zone, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for gcp_builder_zone_arm, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for gcp_base_image_debian12_x86_64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for gcp_base_image_debian12_arm64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for script_debug, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_ubuntu2004_arm64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_macos14_x86_64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_ubuntu2004_x86_64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for gcp_base_image_debian11_x86_64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_debian11_arm64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_macos14_arm64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_builder_region, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_debian12_x86_64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_macos_builder_region, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_xxxxx_debian_11_x86_64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_debian11_x86_64, so skipping
2025/02/10 10:26:28 [TRACE] validateValue: not active for aws_base_image_ubuntu2404_x86_64, so skipping
2025/02/10 10:26:28 waiting for all plugin processes to complete...
panic: interface conversion: interface is nil, not dag.Vertex

goroutine 1 [running]:
github.com/hashicorp/packer/internal/dag.stronglyConnected(0xc0008f88e0, 0xc000527300, {0x1771840, 0xc0006dd9a0})
	github.com/hashicorp/packer/internal/dag/tarjan.go:31 +0x4fb
github.com/hashicorp/packer/internal/dag.StronglyConnected(0xc000527300)
	github.com/hashicorp/packer/internal/dag/tarjan.go:19 +0x267
github.com/hashicorp/packer/internal/dag.(*AcyclicGraph).Cycles(0x5041a6?)
	github.com/hashicorp/packer/internal/dag/dag.go:62 +0x19
github.com/hashicorp/packer/internal/dag.(*AcyclicGraph).Validate(0xc000527300)
	github.com/hashicorp/packer/internal/dag/dag.go:34 +0x2a
github.com/hashicorp/packer/hcl2template.(*PackerConfig).buildPrereqsDAG(0xc00058c000)
	github.com/hashicorp/packer/hcl2template/parser.go:446 +0x732
github.com/hashicorp/packer/hcl2template.(*PackerConfig).evaluateBuildPrereqs(0xc00058c000, 0x0)
	github.com/hashicorp/packer/hcl2template/parser.go:459 +0x69
github.com/hashicorp/packer/hcl2template.(*PackerConfig).Initialize(0xc00058c000, {0x60?, 0x2f?})
	github.com/hashicorp/packer/hcl2template/parser.go:524 +0x32e
github.com/hashicorp/packer/command.(*BuildCommand).RunContext(0xc0005dede0, {0x1fea400, 0xc000540140}, 0xc000736000)
	github.com/hashicorp/packer/command/build.go:105 +0xed
github.com/hashicorp/packer/command.(*BuildCommand).Run(0xc0005dede0, {0xc00003e0c0, 0x3, 0x3})
	github.com/hashicorp/packer/command/build.go:45 +0xbb
github.com/mitchellh/cli.(*CLI).Run(0xc00058cf00)
	github.com/mitchellh/[email protected]/cli.go:262 +0x5b8
main.wrappedMain()
	github.com/hashicorp/packer/main.go:274 +0xeac
main.realMain()
	github.com/hashicorp/packer/main.go:51 +0xd5
main.main()