feat: add Add-PSDepend command to append dependencies to a DependencyFile

[HeyItsGilbert]

Summary

Add-PSDepend <Name> <Version>
  Resolve-PSDependFileTarget          # discover/fallback to requirements.psd1
  Import-LocalizedData                # read existing entries + PSDependOptions
  (collision check, DependencyType default resolution, entry-format choice)
  [AST] Parser::ParseInput + splice   # insert new entry as text, rest untouched
  Set-Content                         # write DependencyFile
  Update-PSDependLock                 # re-lock, unless -NoLock
    on failure → restore original file text, rethrow

Closes #26 (first opened 2017, revisited now that requirements.lock.json exists — see the design interview on the issue and docs/adr/0001-add-psdepend-file-writer-and-lock-behavior.md).

 PSDepend/
 ├── Public/
+│   └── Add-PSDepend.ps1
 ├── Private/
+│   ├── Resolve-PSDependFileTarget.ps1   # file discovery + 0/1/2+ fallback rule
+│   └── ConvertTo-PSDependLiteral.ps1    # psd1 literal serializer for entry values
 Tests/
+└── Add-PSDepend.Tests.ps1               # 22 tests
 docs/adr/
+└── 0001-add-psdepend-file-writer-and-lock-behavior.md

Add-PSDepend psake latest
# @{ 'psake' = 'latest' }, then re-locks automatically

Add-PSDepend -DependencyType GitHub -Name 'RamblingCookieMonster/PowerShell' -Version main
# @{ 'RamblingCookieMonster/PowerShell' = @{ DependencyType = 'GitHub'; Version = 'main' } }

Key decisions (full rationale in the ADR):

• No new dependency. The original issue thread suggested PoshCode/Metadata, but Export-Metadata reformats the whole file (drops comments everywhere, not just the new entry) and Update-Metadata can't add new keys at all. Hand-rolled AST splicing only touches the new entry's text.
• Lock stays honest. Add-PSDepend re-runs Update-PSDependLock by default (-NoLock to skip) and rolls back the file edit if resolution fails, so the DependencyFile and its lock can't silently drift the way they could before locks existed.
• Declare-only. Mirrors the command name; installing is still a separate Invoke-PSDepend call.

Evidence

Before: no Add-PSDepend command; the only way to add a dependency was to hand-edit requirements.psd1.

After:

Tests Passed: 646, Failed: 0, Skipped: 66, Inconclusive: 0, NotRun: 0

(./build.ps1 Pester5 — full suite, including 22 new Add-PSDepend tests covering discovery, entry format, DependencyType default resolution, collisions/-Force, comment preservation, lock auto-update/rollback, -WhatIf, and validation. ./build.ps1 Analyze is clean for the new files.)

Smoke-tested end-to-end against the live PowerShell Gallery:

PS> Add-PSDepend -Name 'Pester' -Version '5.9.0' -PassThru
/tmp/.../requirements.psd1
PS> Get-Content requirements.lock.json
{
  "packages": { "PSGalleryModule::Pester": { "version": "5.9.0", ... } }
}

Merge Danger

Door: Two-way. New command, zero changes to existing public functions or the DependencyFile schema; nothing else depends on Add-PSDepend yet, so reverting is a plain revert.

Blast Radius: New surface only. Touches no existing code paths — Get-Dependency, Invoke-PSDepend, and Update-PSDependLock are unmodified (only called, not edited). The one behavioral nuance: by default Add-PSDepend makes a network call (via Update-PSDependLock) to resolve the new dependency's version — documented in the README/about-topic and avoidable with -NoLock.

[github-actions]

Test Results

    3 files     96 suites   2m 23s ⏱️
1 583 tests 1 523 ✅ 60 💤 0 ❌
2 217 runs  2 147 ✅ 70 💤 0 ❌

Results for commit 6249edd.

♻️ This comment has been updated with latest results.

[Copilot]

🟡 Changes recommended

Literal serialization and file-writing behavior can produce invalid files or alter content outside the inserted entry.

6 open findings

• Preserve original encoding and fail writes before lock generation · New
• Quote hashtable parameter keys during serialization · New
• Serialize empty enumerables as empty array literals · New
• Reject existing non-PSD1 files before editing · New
• Preserve file suffix and newline style in append mode · New
• Document key-only Name behavior for dependency entries · New

What changed in this PR

Adds Add-PSDepend for creating or updating DependencyFiles while optionally refreshing locks.

Changes:

• Adds dependency discovery, serialization, insertion, collision handling, and rollback.
• Exports and documents the new command.
• Adds comprehensive Pester coverage and an architectural decision record.

File	Description
PSDepend/​Public/​Add-PSDepend.ps1	Implements the command and lock integration.
PSDepend/​Private/​Resolve-PSDependFileTarget.ps1	Resolves the target DependencyFile.
PSDepend/​Private/​ConvertTo-PSDependLiteral.ps1	Serializes dependency values.
PSDepend/​PSDepend.psd1	Exports the command.
Tests/​Add-PSDepend.Tests.ps1	Tests command behavior.
README.md	Documents common usage.
PSDepend/​en-US/​about_PSDepend.help.txt	Adds conceptual help.
docs/​adr/​0001-add-psdepend-file-writer-and-lock-behavior.md	Records design decisions.
CHANGELOG.md	Announces the feature.

🧠 Review effort: Balanced

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[HeyItsGilbert]

Addressed all 6 Copilot review findings in 1f14a50 (replied inline on each): original file encoding/BOM is now preserved and writes are terminating so a failed write can't fall through to the lock step, newline style and blank lines before the closing brace are preserved instead of trimmed, Resolve-PSDependFileTarget rejects existing non-.psd1 files, ConvertTo-PSDependLiteral quotes hashtable keys and emits @() for empty arrays, and the .PARAMETER Name help text no longer claims a Name field is emitted. Added 9 regression tests, one per fix. Full suite: 655 passed / 0 failed; Analyze clean.

[Copilot]

🟡 Changes recommended

Collision handling and literal serialization currently permit duplicate logical dependencies and alter some parameter values.

1 open finding

• Preserve embedded CRLF sequences in string values · New

6 resolved since last review

• Preserve original encoding and fail writes before lock generation
• Preserve file suffix and newline style in append mode
• Reject existing non-PSD1 files before editing
• Serialize empty enumerables as empty array literals
• Quote hashtable parameter keys during serialization
• Document key-only Name behavior for dependency entries

Previously missed (2)

In code that hasn't changed since last review

Serialize all supported numeric parameter types correctly

PSDepend/​Private/​ConvertTo-PSDependLiteral.ps1:50

Despite documenting support for “numbers,” only Int32, Int64, and Double are serialized numerically. Other standard numeric values accepted through -Parameters—such as Decimal, Single, UInt32, or Int16—fall through to the quoted-string branch and silently change type when the file is re-imported. Serialize all supported numeric primitives as valid invariant PowerShell literals, or reject unsupported numeric types instead of converting them to strings.

This issue also appears on line 57 of the same file.

Normalize helper syntax during dependency collision detection

PSDepend/​Public/​Add-PSDepend.ps1:236

The collision check compares only the raw PSD1 key, so it misses PSDepend's documented helper syntax. For example, an existing 'PSGalleryModule::Pester' = '4.0.0' is parsed by Get-Dependency as DependencyName = 'Pester', but Add-PSDepend Pester ... appends a second logical Pester dependency instead of throwing or replacing it. Normalize helper-form string entries to their suffix during collision detection, retain the original key for the AST replacement, and match that original key at line 310.

🧠 Review effort: Balanced