fix(install): skip missing patch files for packages not in dependency graph

When `patchedDependencies` references a patch file that doesn't exist on
disk, `bun install` now only errors if the patched package is actually
part of the resolved dependency graph. This fixes pruned monorepo
contexts (e.g. `turbo prune --docker`) where the root `package.json`
may reference patches for packages only used by other workspaces.

Closes #26969

Co-Authored-By: Claude <noreply@anthropic.com>

src/install/lockfile.zig

@@ -780,10 +780,16 @@ pub fn cleanWithLogger(
 
     {
         var builder = new.stringBuilder();
-        for (old.patched_dependencies.values()) |patched_dep| builder.count(patched_dep.path.slice(old.buffers.string_bytes.items));
+        for (old.patched_dependencies.values()) |patched_dep| {
+            // Skip entries whose patch hash was never calculated — this means
+            // the patched package was not part of the resolved dependency graph
+            // (e.g. patchedDependencies in a pruned monorepo root).
+            if (patched_dep.patchfile_hash_is_null) continue;
+            builder.count(patched_dep.path.slice(old.buffers.string_bytes.items));
+        }
         try builder.allocate();
         for (old.patched_dependencies.keys(), old.patched_dependencies.values()) |k, v| {
-            bun.assert(!v.patchfile_hash_is_null);
+            if (v.patchfile_hash_is_null) continue;
             var patchdep = v;
             patchdep.path = builder.append(String, patchdep.path.slice(old.buffers.string_bytes.items));
             try new.patched_dependencies.put(new.allocator, k, patchdep);

src/install/patch_install.zig

@@ -147,6 +147,12 @@ pub const PatchTask = struct {
         // need to switch on version.tag and handle each case appropriately
         const calc_hash = &this.callback.calc_hash;
         const hash = calc_hash.result orelse {
+            // For pre-calculation tasks, a null result means the patch file was not
+            // found on disk. This is not fatal — the patched package may not be in
+            // the current dependency graph (e.g. pruned monorepo / turbo prune).
+            // If the package IS later resolved, determinePreinstallState will
+            // trigger a new (non-pre) hash calculation that will properly error.
+            if (this.pre) return;
             if (log_level != .silent) {
                 if (calc_hash.logger.hasErrors()) {
                     calc_hash.logger.print(Output.errorWriter()) catch {};
@@ -419,6 +425,13 @@ pub const PatchTask = struct {
         const stat: bun.Stat = switch (bun.sys.stat(absolute_patchfile_path)) {
             .err => |e| {
                 if (e.getErrno() == .NOENT) {
+                    // If this is a pre-calculation task (no associated package in the
+                    // dependency graph yet), the patch file being missing is not an error —
+                    // the patched package may simply not be part of the current dependency
+                    // graph (e.g. in a pruned monorepo). If the package IS later resolved,
+                    // determinePreinstallState will trigger a non-pre hash calculation
+                    // that will properly report the error.
+                    if (this.pre) return null;
                     bun.handleOom(log.addErrorFmt(null, Loc.Empty, this.manager.allocator, "Couldn't find patch file: '{s}'\n\nTo create a new patch file run:\n\n  <cyan>bun patch {s}<r>", .{
                         this.callback.calc_hash.patchfile_path,
                         this.manager.lockfile.patched_dependencies.get(this.callback.calc_hash.name_and_version_hash).?.path.slice(this.manager.lockfile.buffers.string_bytes.items),

test/regression/issue/26969.test.ts

@@ -0,0 +1,31 @@
+import { expect, test } from "bun:test";
+import { bunEnv, bunExe, tempDir } from "harness";
+
+// https://github.com/oven-sh/bun/issues/26969
+// bun install should not fail when patchedDependencies references a patch file
+// that doesn't exist, as long as the patched package is not in the dependency graph.
+test("bun install succeeds when patchedDependencies patch file is missing but package is not in dependency graph", async () => {
+  using dir = tempDir("issue-26969", {
+    "package.json": JSON.stringify({
+      name: "repro-26969",
+      private: true,
+      patchedDependencies: {
+        "next-auth@5.0.0": "patches/next-auth@5.0.0.patch",
+      },
+    }),
+  });
+
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "install"],
+    env: bunEnv,
+    cwd: String(dir),
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+  // Should not error about missing patch file
+  expect(stderr).not.toContain("Couldn't find patch file");
+  expect(exitCode).toBe(0);
+});