Fix install for projects with workspaces

src/tmpl/yarn-project.nix.in

@@ -154,8 +154,13 @@ let
       mkdir -p "$out/libexec/$name" "$out/bin"
 
       # Move the package contents to the output directory.
+      if grep -q '"workspaces"' package.json; then
+        # We can't use `yarn pack` in a workspace setup, because it only
+        # packages the outer workspace.
+        mv $PWD "$out/libexec/$name"
+      else
         # - If the package.json has a `files` field, only files matching those patterns are copied
-      # - Otherwise all files are copied
+        # - Otherwise all files are copied.
         yarn pack --out package.tgz
         tar xzvf package.tgz --directory "$out/libexec/$name" --strip-components=1
 
@@ -170,6 +175,7 @@ let
           # Otherwise, assume PnP. Copy the loader into the package.
           cp .pnp.* "$out/libexec/$name"
         fi
+      fi
 
       cd "$out/libexec/$name"