feat(ENG-13677): Terraform credential helper

[tigh-latte]

Description

Adds a Terraform credentials helper for Cloudsmith registries so
terraform init can authenticate against a Cloudsmith Terraform registry with
no token on disk, reusing the existing Cloudsmith CLI credential chain
(--api-key/CLOUDSMITH_API_KEY, credentials.ini, the OS keyring, or OIDC).

Terraform discovers credentials helpers as executables named
terraform-credentials-<name> and only searches its plugin directories (never
$PATH). This PR ships the helper, a launcher/wrapper that satisfies that
discovery contract, an installer that wires up ~/.terraformrc, and the
repository-scoped token format the registry expects.

What's included

Command (cloudsmith credential-helper terraform)

• Implements Terraform's credentials-helper protocol for the get verb.
  Accepts Terraform's [verb] <hostname> calling convention (verb defaults to
  get; hostname falls back to stdin) so the launcher can forward args
  verbatim.
• Returns {"token": "..."} for a Cloudsmith host and {} for any other host
  (exit 0) so Terraform falls back to its own credential sources.
  store/forget and unknown verbs return an actionable error and a non-zero
  exit. Missing credentials for a Cloudsmith host produce a clean refusal, never
  a traceback.
• Registered on the credential-helper group.

Installer (credential-helper install/uninstall/list terraform)

• Writes the launcher into Terraform's plugin dir (~/.terraform.d/plugins by
  default; --bin-dir overrides) and manages the credentials_helper "cloudsmith" block in ~/.terraformrc via a regex block editor (no HCL
  parser); refuses if a different helper block already exists.
• Bakes the resolved --org, -P/--profile, and --repo into the terraformrc
  args list so terraform init needs no environment variables. Computes the
  terraformrc change before writing the launcher so a conflict leaves no orphan.

Repository-scoped, custom-domain-aware token format

• Terraform never tells a credentials helper which repository is requested, so
  -r/--repo/--repository (or CLOUDSMITH_REPO) is required on get, and
  can also be passed to install to bake it into the terraformrc args.
• Tokens are scoped per repository:
  • Standard *.cloudsmith.io/*.cloudsmith.com hosts → {org}/{repo}/{token}
    (the organisation is required here).
  • Custom domains (already bound to a single organisation) → {repo}/{token}
    (the org is used only to resolve the domain, never emitted in the token).
• Added is_standard_cloudsmith_domain() to credential_helpers/common.py to
  distinguish standard hosts from custom domains (is_cloudsmith_domain was
  refactored to reuse it; behaviour unchanged).

Type of Change

• New feature

Testing

• Unit tests for the runtime (get/store/forget, token / empty-object /
  refusal outcomes, org-required-on-standard-domain, org-omitted-on-custom-
  domain), the CLI shim, the wrapper delegation, the terraformrc block
  helpers, and the installer (launcher + terraformrc, --org/-P/--repo
  baking, conflict handling).
• is_standard_cloudsmith_domain unit coverage (apex/subdomain/scheme/casing
  matches, plus custom-domain and lookalike non-matches).
• A live integration test (@pytest.mark.integration) that runs a real
  terraform init in an isolated HOME and asserts it does not fail for
  authentication reasons; skips cleanly when terraform, the wrapper, or the
  PYTEST_CLOUDSMITH_* vars are absent.

env -u CLOUDSMITH_PROFILE -u CLOUDSMITH_ORG -u CLOUDSMITH_WORKSPACE \
    -u CLOUDSMITH_KEYRING_BACKEND HOME=$(mktemp -d) \
    pytest -m "not integration"

Additional Notes

• Auth with a JWT is dependent on https://github.com/cloudsmith-io/cloudsmith/pull/16538 being merged and released
  terraformrc block management, the required repo flag, and the token format).

[Copilot]

Pull request overview

Adds a Terraform credentials helper integration to Cloudsmith CLI so terraform init can authenticate against Cloudsmith Terraform registries via the existing CLI credential chain (env/config/keyring/OIDC), plus installer logic to wire Terraform’s plugin dir and ~/.terraformrc.

Changes:

• Introduces Terraform helper runtime + terraformrc block editor + installer that writes a terraform-credentials-cloudsmith launcher into Terraform’s plugin directory and manages a credentials_helper "cloudsmith" block.
• Adds CLI wiring for cloudsmith credential-helper terraform and extends credential-helper install to support Terraform-specific baked args (org/profile/repo) and next-steps guidance.
• Adds unit + integration tests and refactors domain detection by introducing is_standard_cloudsmith_domain().

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
cloudsmith_cli/credential_helpers/terraform/terraformrc.py	Text-based add/update/remove of the credentials_helper "cloudsmith" terraformrc block.
cloudsmith_cli/credential_helpers/terraform/runtime.py	Implements Terraform credentials-helper protocol behavior and scoped token formatting.
cloudsmith_cli/credential_helpers/terraform/installer.py	Installs/removes the launcher into Terraform plugin dir and updates terraformrc.
cloudsmith_cli/credential_helpers/terraform/init.py	Exposes Terraform helper runtime functions at package level.
cloudsmith_cli/credential_helpers/common.py	Adds is_standard_cloudsmith_domain() and reuses it in is_cloudsmith_domain().
cloudsmith_cli/cli/commands/credential_helper/terraform.py	Click command shim for Terraform helper (parses verb/hostname, prints JSON).
cloudsmith_cli/cli/commands/credential_helper/manage.py	Registers Terraform installer; adds Terraform repo bake + next-steps output.
cloudsmith_cli/cli/commands/credential_helper/init.py	Registers the terraform subcommand under credential-helper.
cloudsmith_cli/cli/tests/test_startup_imports.py	Adds import-safety tests for Terraform helper (and wrapper).
cloudsmith_cli/cli/tests/test_credential_helper_terraform.py	Adds runtime/CLI/wrapper behavior tests for Terraform helper.
cloudsmith_cli/cli/tests/test_credential_helper_terraform_installer.py	Adds terraformrc + installer + CLI install/uninstall tests.
cloudsmith_cli/cli/tests/commands/test_credential_helper.py	Adds unit coverage for is_standard_cloudsmith_domain().
cloudsmith_cli/cli/tests/commands/test_credential_helper_terraform_integration.py	Adds live terraform init integration test exercising helper auth path.
CHANGELOG.md	Documents the new Terraform credentials helper feature.

Suppressed comments (1)

cloudsmith_cli/cli/tests/test_startup_imports.py:76

• This test imports cloudsmith_cli.credential_helpers.terraform.wrapper, but there is no wrapper.py under cloudsmith_cli/credential_helpers/terraform/ in this PR (only __init__.py, runtime.py, installer.py, terraformrc.py). This will fail at import time and break the suite.

Either add the missing wrapper module (and its packaging entry point if it’s meant to be an installed executable), or adjust/remove the wrapper-related tests if the launcher written by TerraformInstaller is the only wrapper being shipped.

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[tigh-latte]

@BartoszBlizniak this is ready for another look now

[BartoszBlizniak]

Two of the three earlier threads (--config-file/--credentials-file baking and draining stdin on store) are fixed correctly, thanks. The plugin-dir restriction needs another pass, see inline.