Crash when planning with an invalid module source in a parent module

[Octogonapus]

Terraform Version

Terraform v1.1.9
on linux_amd64
+ provider registry.terraform.io/hashicorp/aws v4.13.0
+ provider registry.terraform.io/hashicorp/external v2.2.2
+ provider registry.terraform.io/hashicorp/local v2.2.2
+ provider registry.terraform.io/hashicorp/null v3.1.1
+ provider registry.terraform.io/hashicorp/random v3.1.3

Terraform Configuration Files

I have a shell script instead of configuration files because the order in which the environments are created, and the order in which the configuration files are edited, is important to reproducing this.

mkdir terraformbug && cd terraformbug
echo 'resource "null_resource" "foo" {}\nmodule "foo" { source = "./submod2" }' > main.tf
mkdir submod1
echo 'module "foo" { source = "../" }' > submod1/main.tf
mkdir submod2
touch submod2/main.tf
terraform init
cd submod1
terraform init
echo 'resource "null_resource" "foo" {}\nmodule "foo" { source = "${path.module}/submod2" }' > ../main.tf
terraform plan

Debug Output

Expected Behavior

I would expect an error like Variables may not be used here. instead of a crash.

Actual Behavior

!!!!!!!!!!!!!!!!!!!!!!!!!!! TERRAFORM CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!!

Terraform crashed! This is always indicative of a bug within Terraform.
Please report the crash with Terraform[1] so that we can fix this.

When reporting bugs, please include your terraform version, the stack trace
shown below, and any additional information which may help replicate the issue.

[1]: https://github.com/hashicorp/terraform/issues

!!!!!!!!!!!!!!!!!!!!!!!!!!! TERRAFORM CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!!

runtime error: invalid memory address or nil pointer dereference
goroutine 54 [running]:
runtime/debug.Stack()
	/usr/local/go/src/runtime/debug/stack.go:24 +0x65
runtime/debug.PrintStack()
	/usr/local/go/src/runtime/debug/stack.go:16 +0x19
github.com/hashicorp/terraform/internal/logging.PanicHandler()
	/home/circleci/project/project/internal/logging/panic.go:55 +0x154
panic({0x2328bc0, 0x418c6d0})
	/usr/local/go/src/runtime/panic.go:1038 +0x215
github.com/hashicorp/terraform/internal/configs/configload.(*Loader).moduleWalkerLoad(0xc00066c460, 0xc0001f7c20)
	/home/circleci/project/project/internal/configs/configload/loader_load.go:64 +0x16c
github.com/hashicorp/terraform/internal/configs/configload.(*Loader).makeModuleWalkerSnapshot.func1(0xc0001f7c20)
	/home/circleci/project/project/internal/configs/configload/loader_snapshot.go:134 +0x54
github.com/hashicorp/terraform/internal/configs.ModuleWalkerFunc.LoadModule(0x2301e80, 0xc00094dba0)
	/home/circleci/project/project/internal/configs/config_build.go:131 +0x1f
github.com/hashicorp/terraform/internal/configs.buildChildModules(0xc00032e8c0, {0x2c05840, 0xc000a80d80})
	/home/circleci/project/project/internal/configs/config_build.go:69 +0x4bd
github.com/hashicorp/terraform/internal/configs.buildChildModules(0xc00032e700, {0x2c05840, 0xc000a80d80})
	/home/circleci/project/project/internal/configs/config_build.go:89 +0x77a
github.com/hashicorp/terraform/internal/configs.BuildConfig(0xc000b7c370, {0x2c05840, 0xc000a80d80})
	/home/circleci/project/project/internal/configs/config_build.go:24 +0x85
github.com/hashicorp/terraform/internal/configs/configload.(*Loader).LoadConfigWithSnapshot(0xc00066c460, {0x26bcd4b, 0x1})
	/home/circleci/project/project/internal/configs/configload/loader_snapshot.go:31 +0xbc
github.com/hashicorp/terraform/internal/backend/local.(*Local).localRunDirect(0x27905f8, 0xc000528b40, 0xc000a952f0, 0x278b954, {0x2c6e728, 0xc00079b080})
	/home/circleci/project/project/internal/backend/local/backend_local.go:135 +0x73
github.com/hashicorp/terraform/internal/backend/local.(*Local).localRun(0xc000325cc0, 0xc000528b40)
	/home/circleci/project/project/internal/backend/local/backend_local.go:98 +0x8d4
github.com/hashicorp/terraform/internal/backend/local.(*Local).opPlan(0xc000325cc0, {0x2c4f078, 0xc000b7a200}, {0x2c4f078, 0xc000b7a240}, 0xc000528b40, 0xc000b7a1c0)
	/home/circleci/project/project/internal/backend/local/backend_plan.go:58 +0x12b
github.com/hashicorp/terraform/internal/backend/local.(*Local).Operation.func1()
	/home/circleci/project/project/internal/backend/local/backend.go:323 +0xc3
created by github.com/hashicorp/terraform/internal/backend/local.(*Local).Operation
	/home/circleci/project/project/internal/backend/local/backend.go:316 +0x445

Steps to Reproduce

Additional Context

References

[alisdair]

Thanks for reporting this and for the helpful reproduction script! I'm able to reproduce the issue on both the v1.1 and v1.2 branches.

[github-actions]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.