flutter: fix iOS build error

From 6df275df3b8694daf16302b407520e3b1dee6724 Mon Sep 17 00:00:00 2001

From: Philip Hayes <philiphayes9@gmail.com>

Date: Thu, 12 Sep 2024 13:23:00 -0700

Subject: [PATCH] fix: cleanup xcode_backend.sh to fix iOS build w/

 `NixOS/nixpkgs` flutter

This patch cleans up `xcode_backend.sh`. It now effectively just runs

`exec $FLUTTER_ROOT/bin/dart ./xcode_backend.dart`.

The previous `xcode_backend.sh` tries to discover `$FLUTTER_ROOT` from

argv[0], even though its presence is already guaranteed (the wrapped

`xcode_backend.dart` also relies on this env).

When using nixpkgs flutter, the flutter SDK directory is composed of several

layers, joined together using symlinks (called a `symlinkJoin`). Without this

patch, the auto-discover traverses the symlinks into the wrong layer, and so it

uses an "unwrapped" `dart` command instead of a "wrapped" dart that sets some

important envs/flags (like `$FLUTTER_ROOT`).

Using the "unwrapped" dart then manifests in this error when compiling, since

it doesn't see the ios build-support artifacts:

```

$ flutter run -d iphone

Running Xcode build...

Xcode build done.                                            6.4s

Failed to build iOS app

Error (Xcode): Target debug_unpack_ios failed: Error: Flutter failed to create a directory at "/<nix-store>/XXXX-flutter-3.24.1-unwrapped/bin/cache/artifacts".

```

---

 packages/flutter_tools/bin/xcode_backend.sh | 25 ++++-----------------

 1 file changed, 4 insertions(+), 21 deletions(-)

diff --git a/packages/flutter_tools/bin/xcode_backend.sh b/packages/flutter_tools/bin/xcode_backend.sh

index 2889d7c8e4..48b9d06c6e 100755

--- a/packages/flutter_tools/bin/xcode_backend.sh

+++ b/packages/flutter_tools/bin/xcode_backend.sh

@@ -6,24 +6,7 @@

 # exit on error, or usage of unset var

 set -euo pipefail

-# Needed because if it is set, cd may print the path it changed to.

-unset CDPATH

-

-function follow_links() (

-  cd -P "$(dirname -- "$1")"

-  file="$PWD/$(basename -- "$1")"

-  while [[ -h "$file" ]]; do

-    cd -P "$(dirname -- "$file")"

-    file="$(readlink -- "$file")"

-    cd -P "$(dirname -- "$file")"

-    file="$PWD/$(basename -- "$file")"

-  done

-  echo "$file"

-)

-

-PROG_NAME="$(follow_links "${BASH_SOURCE[0]}")"

-BIN_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"

-FLUTTER_ROOT="$BIN_DIR/../../.."

-DART="$FLUTTER_ROOT/bin/dart"

-

-"$DART" "$BIN_DIR/xcode_backend.dart" "$@"

+# Run `dart ./xcode_backend.dart` with the dart from $FLUTTER_ROOT.

+dart="${FLUTTER_ROOT}/bin/dart"

+xcode_backend_dart="${BASH_SOURCE[0]%.sh}.dart"

+exec "${dart}" "${xcode_backend_dart}" "$@"

-- 

2.46.0