refactor: dedupe PATH prepend helpers

src/infra/path-prepend.ts

@@ -0,0 +1,58 @@
+import path from "node:path";
+
+export function normalizePathPrepend(entries?: string[]) {
+  if (!Array.isArray(entries)) {
+    return [];
+  }
+  const seen = new Set<string>();
+  const normalized: string[] = [];
+  for (const entry of entries) {
+    if (typeof entry !== "string") {
+      continue;
+    }
+    const trimmed = entry.trim();
+    if (!trimmed || seen.has(trimmed)) {
+      continue;
+    }
+    seen.add(trimmed);
+    normalized.push(trimmed);
+  }
+  return normalized;
+}
+
+export function mergePathPrepend(existing: string | undefined, prepend: string[]) {
+  if (prepend.length === 0) {
+    return existing;
+  }
+  const partsExisting = (existing ?? "")
+    .split(path.delimiter)
+    .map((part) => part.trim())
+    .filter(Boolean);
+  const merged: string[] = [];
+  const seen = new Set<string>();
+  for (const part of [...prepend, ...partsExisting]) {
+    if (seen.has(part)) {
+      continue;
+    }
+    seen.add(part);
+    merged.push(part);
+  }
+  return merged.join(path.delimiter);
+}
+
+export function applyPathPrepend(
+  env: Record<string, string>,
+  prepend: string[] | undefined,
+  options?: { requireExisting?: boolean },
+) {
+  if (!Array.isArray(prepend) || prepend.length === 0) {
+    return;
+  }
+  if (options?.requireExisting && !env.PATH) {
+    return;
+  }
+  const merged = mergePathPrepend(env.PATH, prepend);
+  if (merged) {
+    env.PATH = merged;
+  }
+}