feat: TF_CLI_ARGS_* Handling

[milldr]

what

• Added logic and warning messages when the user specifies any TF_CLI_* environment variable, since this may conflict with Atmos behavior.
• Added to 2 places: terraform shell and to any terraform command, since these are handled separately
• Append any TF_CLI env vars to the determined TF_CLI env var for terraform shell

why

• When executing Terraform Shell, we should append generate var file to the (if) specified env var rather than overwriting it
• When executing Terraform, var files are already appended (merged). We should add a warning nonetheless

references

• DEV-2793

atmos terraform shell

atmos terraform plan

Summary by CodeRabbit

Summary by CodeRabbit

• New Features

  • Enhanced logging to alert users about potential conflicts with Terraform environment variables.
  • Improved handling of -var-file arguments to respect existing configurations.

• Bug Fixes

  • Enhanced management of Terraform command-line arguments to prevent unintentional overwriting of variable files.

[coderabbitai]

📝 Walkthrough

Walkthrough

The pull request modifies the handling of Terraform command-line arguments and environment variables within the Atmos shell utility functions. It introduces a structured approach to manage -var-file arguments and implements a warning system for existing environment variables. The changes ensure that existing configurations are respected, preventing unintentional overwrites and enhancing logging for potential conflicts with Terraform-related environment variables.

Changes

File	Change Summary
internal/exec/shell_utils.go	Updated execTerraformShellCommand to improve handling of -var-file arguments for Terraform commands.
internal/exec/terraform.go	Introduced logging for environment variables starting with TF_ to warn users about potential conflicts.

Assessment against linked issues

Objective	Addressed	Explanation
Warn about TF_CLI_ env variable replacement [DEV-2793]	✅
Append to existing environment variables instead of replacing	✅

Possibly related PRs

• add support for disabling custom terraform shell prompt #786: Modifies the execTerraformShellCommand function in the same file, focusing on shell command execution logic.
• increment ATMOS_SHLVL each time atmos terraform shell is called #803: Alters the execTerraformShellCommand function to manage the ATMOS_SHLVL environment variable.
• Export configuration information in shell launched by Atmos #827: Changes to the execTerraformShellCommand function to add environment variables for Terraform operations.
• Add support for atmos terraform providers commands #866: Introduces new commands related to Terraform providers, which may interact with the command execution logic.

Suggested reviewers

• Gowiem
• aknysh
• osterman

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📥 Commits

Reviewing files that changed from the base of the PR and between b8245ca and a9969ad.

📒 Files selected for processing (1)

• internal/exec/shell_utils.go (2 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• internal/exec/shell_utils.go

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

internal/exec/terraform.go (1)

262-264: Catching var-file collisions in component environment ensures thorough coverage.
These lines do a great job of warning users when environment-level settings might be overridden.

📜 Review details

Configuration used: .coderabbit.yaml
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 1aa75c6 and 42c3026.

📒 Files selected for processing (2)

• internal/exec/shell_utils.go (1 hunks)
• internal/exec/terraform.go (1 hunks)

🔇 Additional comments (4)

internal/exec/shell_utils.go (3)

188-190: Neat definition of terraform commands.
This approach centralizes the commands that may require var-file handling, simplifying future maintenance and extension.

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191-197: Clear warning message for potential collisions.
It is helpful to log a warning whenever these TF_CLI_ARGS variables contain a “-var-file” argument, reducing user confusion.

---

198-200: Appending the var file reference to each command is straightforward.
Ensure users understand that this logic overrides any existing “-var-file” specification at runtime.

internal/exec/terraform.go (1)

248-257: Collisions detection is consistent with shell_utils.
Capturing conflicts across both the shell and terraform commands maintains consistent user visibility.

[osterman]

Here's the misunderstanding.

1. execTerraformShellCommand is only called for atmos terraform shell (in your screenshots you're running other commands)
2. The 5th argument is the var file.
3. When running atmos terraform shell, it will squash the TF_CLI_ARG_* environment variables. Not just when we're passing a -var-file. E.g. Setting TF_CLI_ARG_plan=-non-existant-flag will break Terraform. Atmos warning that the ENV is set, will alert the user during debugging.

Here are the new requirements

1. Anytime we execute terraform we should probably warn emit a warning if any of these variables are set, as it can change the deterministic behavior of atmos
2. Modify execTerraformShellCommand so that it does not squash the values of TF_CLI_ARG_* and instead appends (with a space) to it.