Powershell

PowerShell Code Standards

This rule file summarizes the PowerShell-specific policies for this repository.

Toolchain

1. Formatting — Invoke-Formatter: Format all PowerShell files via PoshQC. MCP command: mcp__drm-copilot__run_poshqc_format
2. Linting — PSScriptAnalyzer: Run PoshQC analyzer with repo settings. MCP command: mcp__drm-copilot__run_poshqc_analyze. Optional autofix: mcp__drm-copilot__run_poshqc_analyze_autofix
3. Type checking: Not applicable for PowerShell; skip to testing.
4. Testing — Pester (v5.x): Run tests via MCP. MCP command: mcp__drm-copilot__run_poshqc_test. Use repo config at scripts/powershell/PoshQC/settings/pester.runsettings.psd1.

Run the toolchain in order: format → analyze → test. Restart from step 1 if any step fails or changes files. Use the MCP server functions; do not substitute VS Code task wrappers.

Compatibility

• All scripts must be compatible with PowerShell 7+ (enforced via PSScriptAnalyzer settings).

Coding Standards

• Prefer advanced functions with CmdletBinding() and named parameters.
• Add [Parameter(Mandatory = $true)] and validation attributes where appropriate.
• Implement ShouldProcess/SupportsShouldProcess for state-changing actions.
• Avoid global state and mutable script-scoped variables; pass data explicitly.
• Avoid Invoke-Expression, plaintext secrets, and hard-coded credentials/paths.
• Use Write-Error/throw for failures; avoid silent catch-alls.
• Use approved verbs and descriptive nouns for function names (PSScriptAnalyzer enforces this).
• Keep scripts cohesive and under 500 lines.

Change Budget

• Direct-mode overall scope: up to 2 production PowerShell files (plus corresponding tests). Requests exceeding this must be routed to powershell-orchestrator per powershell-change-budget-router.
• Per-batch cap in all modes: at most 3 production files and 3 test files unless an explicit override has been approved.
• If a batch would exceed the cap, split the work into smaller batches.

Design Seams (Minimal DI)

Introduce the smallest seam that enables reliable mocking. Apply these options in order:

1. Wrapper function seam (preferred) — extract external executable calls into a wrapper function:
   • Signature: Invoke-<Tool>Exe -<Tool>Args <string[]> (for example Invoke-GitExe -GitArgs <string[]>).
   • The wrapper accepts a single array parameter and splats into the executable: git @GitArgs 2>&1.
   • Parameter names must not be Args (automatic variable collision). Use GitArgs, ToolArgs, or Arguments.
2. Injectable delegate / ScriptBlock seam — only when a wrapper is insufficient, add a narrowly-scoped optional delegate or ScriptBlock parameter with a safe default. Do not introduce generic runner frameworks.
3. Adapter seams for non-executable boundaries — for filesystem, environment, or clock dependencies, introduce tiny helpers or narrow injectable parameters rather than threading raw I/O through domain logic.

Testing Standards

• Use Pester (v5.x) as the test framework.
• Organize tests to mirror code structure (e.g., tests/scripts/dev-tools/ScriptName.Tests.ps1).
• Name test files *.Tests.ps1.
• Use Describe/Context/It blocks; one behavior per It.
• Write focused tests exercising a single function or behavior.
• Mock sparingly; prefer real code paths.
• No external dependencies in unit tests.
• Repository-wide line coverage must remain >= 80%.
• Any new module, class, or method must reach >= 90% coverage.
• Coverage regression on changed lines is a blocking finding.

Deterministic Test Requirements

Tests must not depend on:

• network access,
• mutable machine PATH or profile state,
• implicit working-directory assumptions,
• external services or live executables.

Tests must produce identical results in Terminal and the VS Code Test Explorer. Assume a different PATH, current working directory, profile, and host when tests are run from Test Explorer; do not rely on ambient environment resolution.

Mocking Rules

1. External executable mocking — never mock git, gh, actionlint, or other executables directly. Mock the wrapper function (for example Invoke-GitExe) instead.
2. Mock signature parity — mock signatures must match production named parameters exactly. Example:
   • production: Invoke-GitExe -GitArgs $gitArgs
   • test mock: param([string[]]$GitArgs)
3. Mock registration order — register mocks before the code under test can resolve commands, so Test Explorer parity is preserved.
4. AST/ScriptBlock import order — when importing script functions via AST or ScriptBlock patterns:
   • dot-source the returned ScriptBlock in the test scope,
   • import dependencies in the correct order,
   • import wrapper seams before mocking them when executable calls exist.

Prohibited Behaviors

• Broad refactors across unrelated scripts or modules.
• Introducing generic process-runner frameworks to replace the wrapper seam pattern.
• Creating PSScriptAnalyzer debt and deferring cleanup.
• Weakening assertions merely to make tests pass.
• Adding sleeps, retries, or timing hacks to stabilize flaky tests.
• Claiming success without running the required toolchain.