feat: accept snake_case environment variable names

[Abhinesh Jha (Abhineshhh)]

Summary

Implements support for snake_case environment variable names while fully preserving the existing concatenated names for backward compatibility.

Closes / fixes:#248

Problem

Environment variables used a hard-to-read concatenated form (e.g. MPF_SUBSCRIPTIONID). Users requested conventional snake_case (e.g. MPF_SUBSCRIPTION_ID) without breaking existing scripts and CI.

Solution

• Derive both env names from each Cobra flag:
  • Legacy:MPF_ + upper(flagName) → MPF_SUBSCRIPTIONID (unchanged behavior)
  • Snake_case:MPF_ + upper(camelToSnake(flagName)) → MPF_SUBSCRIPTION_ID
• Bind both via Viper BindEnv for every flag (global, ARM, Bicep, Terraform)
• Precedence: CLI flags > legacy env > snake_case env
• Document preferred + legacy forms in the flag reference
• E2E tests accept either form via a small mpfEnv() helper (legacy first)

Examples

Flag	Preferred env	Legacy env (still works)
subscriptionID	MPF_SUBSCRIPTION_ID	MPF_SUBSCRIPTIONID
spClientID	MPF_SP_CLIENT_ID	MPF_SPCLIENTID
templateFilePath	MPF_TEMPLATE_FILE_PATH	MPF_TEMPLATEFILEPATH
tfPath	MPF_TF_PATH	MPF_TFPATH

Changes

Area	Files
CLI binding	cmd/envbinding.go, cmd/rootCmd.go
Unit tests	cmd/envbinding_test.go
Docs	docs/commandline-flags-and-env-variables.md, README.md, AGENTS.md
E2E alignment	e2eTests/env_helpers.go + e2e test files

Backward compatibility

• Existing MPF_SUBSCRIPTIONID, MPF_TFPATH, etc. continue to work
• If both forms are set, legacy wins so current deployments are not surprised
• No flag renames, no dependency changes, no changes to deploy/permission logic under pkg/

Test plan

• go test ./cmd/ -count=1
• go test ./pkg/... -count=1
• go test ./e2eTests/ -count=1 (compile / unit path; live Azure e2e not run in this environment)
• go vet ./cmd/ ./e2eTests/
• gofmt clean on touched Go files
• Unit coverage for: snake_case only, legacy only, both set (legacy wins), CLI overrides env, terraform flags, initializeConfig with root+arm flags

References

• Issue: Feature Request: Support snake_case environment variable names in addition to current format #248
• Related docs updated: docs/commandline-flags-and-env-variables.md

[Copilot]

Pull request overview

Adds support for snake_case environment variables across the azmpf CLI (via Cobra/Viper), while preserving and prioritizing the existing legacy concatenated env var names for backward compatibility (per issue #248).

Changes:

• Implement dual env var binding per flag (legacy + snake_case) with legacy precedence via centralized binding logic in cmd/envbinding.go.
• Add unit coverage for camel→snake conversion, env name derivation, and binding precedence/behavior.
• Align docs and E2E tests to accept either env var form (legacy-first lookup helper).

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
README.md	Updates examples to prefer snake_case env vars while noting legacy compatibility.
docs/commandline-flags-and-env-variables.md	Documents snake_case vs legacy naming rules and lists both env var forms per flag.
cmd/rootCmd.go	Switches config initialization to use the new dual-env binding helper.
cmd/envbinding.go	Introduces camel→snake conversion, env name derivation, and dual BindEnv behavior.
cmd/envbinding_test.go	Adds unit tests for conversion, env name generation, and precedence (CLI > legacy env > snake_case).
e2eTests/env_helpers.go	Adds mpfEnv() helper to read legacy-first, then snake_case env vars in tests.
e2eTests/e2eTerraformWithImportAndTargeting_test.go	Updates terraform path env lookup to accept both env var forms.
e2eTests/e2eTerraformInvalid_test.go	Updates terraform path env lookup to accept both env var forms.
e2eTests/e2eTerraformAuthPermissionMismatch_test.go	Updates terraform path env lookup to accept both env var forms.
e2eTests/e2eTerraformAuthorizationRequestDenied_test.go	Updates terraform path env lookup to accept both env var forms.
e2eTests/e2eTerraform_test.go	Updates terraform path env lookup to accept both env var forms.
e2eTests/e2eBicepInvalid_test.go	Updates bicep exec path env lookup to accept both env var forms.
e2eTests/e2eBicep_test.go	Updates bicep exec path env lookup to accept both env var forms.
e2eTests/e2eArm_test.go	Updates ARM E2E env var reads to accept both legacy and snake_case forms.
AGENTS.md	Updates agent instructions/examples to use snake_case env vars (preferred).

[Mani Bindra (maniSbindra)]

Abhinesh Jha (@Abhineshhh) Thanks for the PR. It looks good. Can you look that linting PR check which is failing

[Mani Bindra (maniSbindra)]

Abhinesh Jha (@Abhineshhh) Thanks for the PR. It looks good. Can you look that linting PR check which is failing

[Abhinesh Jha (Abhineshhh)]

Mani Bindra (@maniSbindra) Thanks for the review. Rebased onto latest main and fixed the failing lint checks:

• markdownlint: aligned tables in docs/commandline-flags-and-env-variables.md
• govulncheck: cleared by rebasing (picks up Only open govulncheck issues for vulnerabilities we actually call #305 and current module versions)
• staticcheck: merged the e2e tfpath declare/assign pairs after the mpfEnv helper change

Also updated the remaining docs examples, including docs/installation-and-quickstart.md, to the preferred snake_case names (legacy names still work).

[Mani Bindra (maniSbindra)]

Thanks Abhinesh Jha (@Abhineshhh) for addressing the feedback and fixing the checks. The PR now looks good to merge.

We’ll hold the merge briefly to coordinate it with the next MPF release. The updated documentation uses snake_case environment variables, which the currently released binary does not yet support. This avoids users following the new examples before a compatible binary is available.

No further changes are required from you.