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element() function is broken with negative indices #36369

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yermulnik opened this issue Jan 20, 2025 · 2 comments · Fixed by #36376
Closed

element() function is broken with negative indices #36369

yermulnik opened this issue Jan 20, 2025 · 2 comments · Fixed by #36376
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bug confirmed a Terraform Core team member has reproduced this issue cty Use in conjunction with "upstream" when cty is the relevant upstream upstream

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@yermulnik
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Terraform Version

Terraform v1.10.4
on linux_amd64

Terraform Configuration Files

> cat ~/.terraformrc
plugin_cache_dir = "$HOME/.terraform.d/plugin-cache"

Debug Output

# running in empty directory
> echo 'element([1,2,3], -1)' | TF_LOG=trace terraform console -no-color
2025-01-21T00:34:03.385+0200 [INFO]  Terraform version: 1.10.4
2025-01-21T00:34:03.385+0200 [DEBUG] using github.com/hashicorp/go-tfe v1.70.0
2025-01-21T00:34:03.385+0200 [DEBUG] using github.com/hashicorp/hcl/v2 v2.23.0
2025-01-21T00:34:03.385+0200 [DEBUG] using github.com/hashicorp/terraform-svchost v0.1.1
2025-01-21T00:34:03.385+0200 [DEBUG] using github.com/zclconf/go-cty v1.16.0
2025-01-21T00:34:03.385+0200 [INFO]  Go runtime version: go1.23.3
2025-01-21T00:34:03.385+0200 [INFO]  CLI args: []string{"terraform", "console", "-no-color"}
2025-01-21T00:34:03.385+0200 [TRACE] Stdout is not a terminal
2025-01-21T00:34:03.385+0200 [TRACE] Stderr is not a terminal
2025-01-21T00:34:03.385+0200 [TRACE] Stdin is not a terminal
2025-01-21T00:34:03.385+0200 [DEBUG] Attempting to open CLI config file: /home/georgii/.terraformrc
2025-01-21T00:34:03.385+0200 [INFO]  Loading CLI configuration from /home/georgii/.terraformrc
2025-01-21T00:34:03.385+0200 [INFO]  Loading CLI configuration from /home/georgii/.terraform.d/credentials.tfrc.json
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory terraform.d/plugins
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory /home/georgii/.terraform.d/plugins
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory /home/georgii/.local/share/terraform/plugins
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory /home/linuxbrew/.linuxbrew/share/terraform/plugins
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory /usr/share/mate/terraform/plugins
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory /usr/share/gnome/terraform/plugins
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory /home/georgii/.local/share/flatpak/exports/share/terraform/plugins
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory /var/lib/flatpak/exports/share/terraform/plugins
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory /usr/local/share/terraform/plugins
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory /usr/share/terraform/plugins
2025-01-21T00:34:03.386+0200 [DEBUG] ignoring non-existing provider search directory /var/lib/snapd/desktop/terraform/plugins
2025-01-21T00:34:03.386+0200 [INFO]  CLI command args: []string{"console", "-no-color"}
2025-01-21T00:34:03.387+0200 [TRACE] Meta.Backend: no config given or present on disk, so returning nil config
2025-01-21T00:34:03.387+0200 [TRACE] Meta.Backend: backend has not previously been initialized in this working directory
2025-01-21T00:34:03.387+0200 [TRACE] Meta.Backend: using default local state only (no backend configuration, and no existing initialized backend)
2025-01-21T00:34:03.387+0200 [TRACE] Meta.Backend: instantiated backend of type <nil>
2025-01-21T00:34:03.387+0200 [DEBUG] checking for provisioner in "."
2025-01-21T00:34:03.387+0200 [DEBUG] checking for provisioner in "/home/georgii/.terraform.versions"
2025-01-21T00:34:03.387+0200 [TRACE] Meta.Backend: backend <nil> does not support operations, so wrapping it in a local backend
2025-01-21T00:34:03.387+0200 [TRACE] backend/local: CLI option -state is overriding state path to terraform.tfstate
2025-01-21T00:34:03.388+0200 [TRACE] backend/local: requesting state manager for workspace "default"
2025-01-21T00:34:03.388+0200 [TRACE] backend/local: state manager for workspace "default" will:
 - read initial snapshot from terraform.tfstate
 - write new snapshots to terraform.tfstate
 - create any backup at terraform.tfstate.backup
2025-01-21T00:34:03.388+0200 [TRACE] backend/local: requesting state lock for workspace "default"
2025-01-21T00:34:03.388+0200 [TRACE] statemgr.Filesystem: preparing to manage state snapshots at terraform.tfstate
2025-01-21T00:34:03.388+0200 [TRACE] statemgr.Filesystem: no previously-stored snapshot exists
2025-01-21T00:34:03.388+0200 [TRACE] statemgr.Filesystem: locking terraform.tfstate using fcntl flock
2025-01-21T00:34:03.388+0200 [TRACE] statemgr.Filesystem: writing lock metadata to .terraform.tfstate.lock.info
2025-01-21T00:34:03.388+0200 [TRACE] backend/local: reading remote state for workspace "default"
2025-01-21T00:34:03.388+0200 [TRACE] statemgr.Filesystem: reading latest snapshot from terraform.tfstate
2025-01-21T00:34:03.388+0200 [TRACE] statemgr.Filesystem: snapshot file has nil snapshot, but that's okay
2025-01-21T00:34:03.388+0200 [TRACE] statemgr.Filesystem: read nil snapshot
2025-01-21T00:34:03.388+0200 [TRACE] backend/local: populating backendrun.LocalRun for current working directory
2025-01-21T00:34:03.389+0200 [TRACE] terraform.NewContext: starting
2025-01-21T00:34:03.389+0200 [TRACE] terraform.NewContext: complete
2025-01-21T00:34:03.389+0200 [DEBUG] Building and walking 'eval' graph
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.ConfigTransformer
2025-01-21T00:34:03.389+0200 [TRACE] ConfigTransformer: Starting for path:
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.ConfigTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.RootVariableTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.RootVariableTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.ModuleVariableTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.ModuleVariableTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.variableValidationTransformer
2025-01-21T00:34:03.389+0200 [TRACE] variableValidationTransformer: adding validation nodes for any existing variable evaluation nodes
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.variableValidationTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.LocalTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.LocalTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.OutputTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.OutputTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.AttachResourceConfigTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.AttachResourceConfigTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.AttachStateTransformer
2025-01-21T00:34:03.389+0200 [DEBUG] Not attaching any node states: overall state is nil
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.AttachStateTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.graphTransformerMulti
2025-01-21T00:34:03.389+0200 [TRACE] (graphTransformerMulti) Executing graph transform *terraform.externalProviderTransformer
2025-01-21T00:34:03.389+0200 [TRACE] (graphTransformerMulti) Completed graph transform *terraform.externalProviderTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] (graphTransformerMulti) Executing graph transform *terraform.ProviderConfigTransformer
2025-01-21T00:34:03.389+0200 [TRACE] (graphTransformerMulti) Completed graph transform *terraform.ProviderConfigTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] (graphTransformerMulti) Executing graph transform *terraform.MissingProviderTransformer
2025-01-21T00:34:03.389+0200 [TRACE] (graphTransformerMulti) Completed graph transform *terraform.MissingProviderTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] (graphTransformerMulti) Executing graph transform *terraform.ProviderTransformer
2025-01-21T00:34:03.389+0200 [TRACE] (graphTransformerMulti) Completed graph transform *terraform.ProviderTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] (graphTransformerMulti) Executing graph transform *terraform.PruneProviderTransformer
2025-01-21T00:34:03.389+0200 [TRACE] (graphTransformerMulti) Completed graph transform *terraform.PruneProviderTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.graphTransformerMulti (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.AttachSchemaTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.AttachSchemaTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.ModuleExpansionTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.ModuleExpansionTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.ReferenceTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.ReferenceTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.CloseProviderTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.CloseProviderTransformer (no changes)
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.CloseRootModuleTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.CloseRootModuleTransformer with new graph:
  root - *terraform.nodeCloseModule
  ------
2025-01-21T00:34:03.389+0200 [TRACE] Executing graph transform *terraform.TransitiveReductionTransformer
2025-01-21T00:34:03.389+0200 [TRACE] Completed graph transform *terraform.TransitiveReductionTransformer (no changes)
2025-01-21T00:34:03.389+0200 [DEBUG] Starting graph walk: walkEval
2025-01-21T00:34:03.389+0200 [TRACE] vertex "root": starting visit (*terraform.nodeCloseModule)
2025-01-21T00:34:03.389+0200 [TRACE] vertex "root": does not belong to any module instance
2025-01-21T00:34:03.389+0200 [TRACE] vertex "root": visit complete

Error: Error in function call

  on <console-input> line 1:
  (source code not available)

Call to function "element" failed: panic in function implementation: runtime
error: index out of range [-1]
goroutine 1 [running]:
runtime/debug.Stack()
	runtime/debug/stack.go:26 +0x5e
github.com/zclconf/go-cty/cty/function.errorForPanic(...)
	github.com/zclconf/go-cty@v1.16.0/cty/function/error.go:44
github.com/zclconf/go-cty/cty/function.Function.returnTypeForValues.func1()
	github.com/zclconf/go-cty@v1.16.0/cty/function/function.go:226 +0x7b
panic({0x352be40?, 0xc0007d1428?})
	runtime/panic.go:785 +0x132
github.com/zclconf/go-cty/cty/function/stdlib.init.func12({0xc0009f5ec0,
0xc0001959e8?, 0x3e20e58?})
	github.com/zclconf/go-cty@v1.16.0/cty/function/stdlib/collection.go:173
+0x25f
github.com/zclconf/go-cty/cty/function.Function.returnTypeForValues({0x0?},
{0xc0009f5ec0, 0x2, 0x0?})
	github.com/zclconf/go-cty@v1.16.0/cty/function/function.go:230 +0x778
github.com/zclconf/go-cty/cty/function.Function.Call({0x3e20e58?},
{0xc0009f5ec0, 0x2, 0x2})
	github.com/zclconf/go-cty@v1.16.0/cty/function/function.go:250 +0x7a
github.com/hashicorp/hcl/v2/hclsyntax.(*FunctionCallExpr).Value(0xc0003ceb40,
0xc0009fa588)
	github.com/hashicorp/hcl/v2@v2.23.0/hclsyntax/expression.go:528 +0x1acf
github.com/hashicorp/terraform/internal/lang.(*Scope).EvalExpr(0xc0007b6480,
{0x3e217e8, 0xc0003ceb40}, {{0x3e218d8?, 0x5a431a0?}})
	github.com/hashicorp/terraform/internal/lang/eval.go:179 +0x1a5
github.com/hashicorp/terraform/internal/repl.(*Session).handleEval(0xc00088f8e8,
{0xc00088f6d8?, 0xc00088f6d8?})
	github.com/hashicorp/terraform/internal/repl/session.go:58 +0x14e
github.com/hashicorp/terraform/internal/repl.(*Session).Handle(0xc00088f8e8,
{0xc00088f6d8, 0x14})
	github.com/hashicorp/terraform/internal/repl/session.go:43 +0xbc
github.com/hashicorp/terraform/internal/command.(*ConsoleCommand).modePiped(0xc000685a40,
0xc00088f8e8, {0x3e290f0, 0xc0009f0330})
	github.com/hashicorp/terraform/internal/command/console.go:191 +0xee
github.com/hashicorp/terraform/internal/command.(*ConsoleCommand).Run(0xc000685a40,
{0xc00018a170?, 0x0?, 0x0?})
	github.com/hashicorp/terraform/internal/command/console.go:181 +0x1073
github.com/hashicorp/cli.(*CLI).Run(0xc0009d2140)
	github.com/hashicorp/cli@v1.1.6/cli.go:265 +0x55f
main.realMain()
	github.com/hashicorp/terraform/main.go:339 +0x1deb
main.main()
	github.com/hashicorp/terraform/main.go:64 +0x13
.

2025-01-21T00:34:03.390+0200 [TRACE] statemgr.Filesystem: removing lock metadata file .terraform.tfstate.lock.info
2025-01-21T00:34:03.390+0200 [TRACE] statemgr.Filesystem: unlocking terraform.tfstate using fcntl flock

Expected Behavior

As of TF 1.10.0 release notes and #35501 I'd expect element() function to accept negative indices and not fail.

Actual Behavior

> echo 'element([1,2,3], -1)' | terraform console -no-color

Error: Error in function call

  on <console-input> line 1:
  (source code not available)

Call to function "element" failed: panic in function implementation: runtime error: index out of range [-1]
goroutine 1 [running]:
runtime/debug.Stack()
        runtime/debug/stack.go:26 +0x5e
github.com/zclconf/go-cty/cty/function.errorForPanic(...)
        github.com/zclconf/go-cty@v1.16.0/cty/function/error.go:44
github.com/zclconf/go-cty/cty/function.Function.returnTypeForValues.func1()
        github.com/zclconf/go-cty@v1.16.0/cty/function/function.go:226 +0x7b
panic({0x352be40?, 0xc000c106a8?})
        runtime/panic.go:785 +0x132
github.com/zclconf/go-cty/cty/function/stdlib.init.func12({0xc000a34780, 0xc000013bf8?, 0x3e20e58?})
        github.com/zclconf/go-cty@v1.16.0/cty/function/stdlib/collection.go:173 +0x25f
github.com/zclconf/go-cty/cty/function.Function.returnTypeForValues({0x0?}, {0xc000a34780, 0x2, 0x0?})
        github.com/zclconf/go-cty@v1.16.0/cty/function/function.go:230 +0x778
github.com/zclconf/go-cty/cty/function.Function.Call({0x3e20e58?}, {0xc000a34780, 0x2, 0x2})
        github.com/zclconf/go-cty@v1.16.0/cty/function/function.go:250 +0x7a
github.com/hashicorp/hcl/v2/hclsyntax.(*FunctionCallExpr).Value(0xc00089a5a0, 0xc000c09d10)
        github.com/hashicorp/hcl/v2@v2.23.0/hclsyntax/expression.go:528 +0x1acf
github.com/hashicorp/terraform/internal/lang.(*Scope).EvalExpr(0xc0002c2ab0, {0x3e217e8, 0xc00089a5a0}, {{0x3e218d8?, 0x5a431a0?}})
        github.com/hashicorp/terraform/internal/lang/eval.go:179 +0x1a5
github.com/hashicorp/terraform/internal/repl.(*Session).handleEval(0xc00081b8e8, {0xc00081b6d8?, 0xc00081b6d8?})
        github.com/hashicorp/terraform/internal/repl/session.go:58 +0x14e
github.com/hashicorp/terraform/internal/repl.(*Session).Handle(0xc00081b8e8, {0xc00081b6d8, 0x14})
        github.com/hashicorp/terraform/internal/repl/session.go:43 +0xbc
github.com/hashicorp/terraform/internal/command.(*ConsoleCommand).modePiped(0xc000584c40, 0xc00081b8e8, {0x3e290f0, 0xc000a0ee10})
        github.com/hashicorp/terraform/internal/command/console.go:191 +0xee
github.com/hashicorp/terraform/internal/command.(*ConsoleCommand).Run(0xc000584c40, {0xc0000721a0?, 0x0?, 0x0?})
        github.com/hashicorp/terraform/internal/command/console.go:181 +0x1073
github.com/hashicorp/cli.(*CLI).Run(0xc000760280)
        github.com/hashicorp/cli@v1.1.6/cli.go:265 +0x55f
main.realMain()
        github.com/hashicorp/terraform/main.go:339 +0x1deb
main.main()
        github.com/hashicorp/terraform/main.go:64 +0x13
.

Steps to Reproduce

echo 'element([1,2,3], -1)' | terraform console

Additional Context

No response

References

Generative AI / LLM assisted development?

No response
@yermulnik yermulnik added bug new new issue not yet triaged labels Jan 20, 2025
@liamcervante liamcervante mentioned this issue Jan 21, 2025
Closed
@liamcervante liamcervante added upstream confirmed a Terraform Core team member has reproduced this issue cty Use in conjunction with "upstream" when cty is the relevant upstream labels Jan 21, 2025
@liamcervante
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Hi @yermulnik, thanks for filing this! I've raised zclconf/go-cty#200 with the upstream function library to resolve this.

I'll note here the difference between a tuple and a list. A tuple is of concrete known length, and so the maintainer of the upstream library may not want to add support for unknown indices when referencing a tuple. I do also note the CHANGELOG for the library (and for Terraform) just said the element function supports negative indices and didn't clarify the difference between a tuple and a list.

While we wait for a response there, you can force the input into a list using the tolist(...) function, so element(tolist([0, 1, 2]), -1) does work as expected.

Thanks again!

@liamcervante liamcervante removed the new new issue not yet triaged label Jan 21, 2025
@yermulnik
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@liamcervante Thanks for filing PR for the underlying library and for the pointer to use list() meanwhile 👍🏻

@liamcervante liamcervante mentioned this issue Jan 22, 2025
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@github-actions github-actions bot mentioned this issue Jan 22, 2025
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update go-cty to latest patch release hashicorp/terraform
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@yermulnik @liamcervante