Resolve and deduplicate the font set once before processing

[MariusStorhaug]

Inside the process block, Install-NerdFont builds the install list with:

foreach ($fontName in $Name) {
    $nerdFontsToInstall += $script:NerdFonts | Where-Object { $_.Name -like $fontName }
}

Two small issues compound across larger inputs:

1. += on an array allocates a new array on every iteration. For pipeline input or many -Name values this is O(n²).
2. Overlapping wildcard patterns produce duplicates — e.g. Install-NerdFont -Name 'Fira*','FiraCode' queues FiraCode twice, doubling the download and extraction work for that font.

Neither issue is visible on tiny inputs, but together they meaningfully slow down -All-adjacent scenarios and waste bandwidth on overlap.

Request

Current experience

Repeated entries in -Name (or repeated pipeline objects) cause the same font to be downloaded, extracted, and installed multiple times in a single command. Building the list also scales quadratically.

Desired experience

The set of fonts to install is resolved once, deduplicated by name, and stored in an efficient collection before any I/O happens. Each font is processed at most once per invocation.

Acceptance criteria

• The function emits exactly one set of download/extract/install operations per unique font, regardless of how many times the name matches via -Name or pipeline input
• Building the install list is linear in the number of inputs
• Verbose output reports the deduplicated count
• Behavior of -All is unchanged (no duplicates exist in that path)

---

Technical decisions

Collection type: Use [System.Collections.Generic.List[object]] to accumulate matches without += reallocation, then project to a unique set keyed by Name.

Dedup key: Font Name is unique in FontsData.json and is a stable, case-insensitive identifier. Use Sort-Object -Unique -Property Name (simple and readable) or a HashSet[string] of seen names while iterating.

Place in the function: Resolution stays in the process block (so pipeline input continues to be supported), but the deduplicated set is materialized once before the per-font loop.

---

Implementation plan

• Replace the += accumulator with [System.Collections.Generic.List[object]]::new() in src/functions/public/Install-NerdFont.ps1
• After resolving matches, deduplicate by Name before entering the install loop
• Update the existing verbose line "Installing [N] fonts" to reflect the deduplicated count
• Add a Pester test that calls Install-NerdFont -Name 'Fira*','FiraCode' and asserts a single install for FiraCode