iOS build error: invalid option: -Dproject_swift_sources

[clsource]

MacOS: Tahoe 26.3
Xcode: 26.5
Mob: 0.6.18

Using a new project it cannot build.

$ mix mob.new calculator
$ cd calculator
$ mix mob.install
$ xcrun simctl boot "iPhone 16e"
$ open -a Simulator

$ mix mob.doctor

Tools
  ✓ version manager — mise (/Users/camilo/.local/bin/mise)
  ✓ Elixir — 1.20.0-rc.5
  ✓ OTP — 29 (ERTS 17.0)
  ✓ Hex — 2.4.2
  ✓ epmd — /Users/camilo/.local/share/mise/installs/erlang/29.0/erts-17.0/bin/epmd
  ✓ adb — /Users/camilo/Library/Android/sdk/platform-tools/adb
  ✓ xcrun — Xcode 26.5
  ✓ zig — 0.16.0
  ✓ java — openjdk version "21.0.11" 2026-04-21 LTS
  ✓ Android SDK — /Users/camilo/Library/Android/sdk
  ✓ Android NDK — 27.2.12479018 (recommended) ✓
  ✓ python3 — /opt/homebrew/bin/python3
  ✓ rsync — /usr/bin/rsync
  ✓ ideviceinfo — /opt/homebrew/bin/ideviceinfo

$ mix mob.deploy --native --ios

$ mix mob.deploy --native --ios

Fetching dependencies...
Resolving Hex dependencies...
Resolution completed in 0.048s
Unchanged:
  bandit 1.11.1
  bunt 1.0.0
  cc_precompiler 0.1.11
  credo 1.7.18
  db_connection 2.10.1
  decimal 3.1.0
  ecto 3.14.0
  ecto_sql 3.14.0
  ecto_sqlite3 0.24.0
  elixir_make 0.9.0
  eqrcode 0.2.1
  ex_ast 0.12.0
  ex_slop 0.4.1
  exqlite 0.36.0
  file_system 1.1.1
  finch 0.22.0
  glob_ex 0.1.11
  hpax 1.0.3
  igniter 0.8.0
  jason 1.4.5
  mime 2.0.7
  mint 1.8.0
  mix_audit 2.1.5
  mob 0.6.18
  mob_dev 0.5.11
  nimble_options 1.1.1
  nimble_parsec 1.4.2
  nimble_pool 1.1.0
  owl 0.13.0
  phoenix 1.8.7
  phoenix_html 4.3.0
  phoenix_live_view 1.1.30
  phoenix_pubsub 2.2.0
  phoenix_template 1.0.4
  plug 1.19.2
  plug_crypto 2.1.1
  req 0.5.18
  rewrite 1.3.0
  sourceror 1.12.0
  spitfire 0.3.12
  telemetry 1.4.2
  text_diff 0.1.0
  thousand_island 1.4.3
  websock 0.5.3
  websock_adapter 0.5.9
  yamerl 0.10.0
  yaml_elixir 2.12.1
All dependencies have been fetched

Deploying to devices...

  Building iOS simulator app...
  === Installing exqlite as OTP library
  === Cross-compiling sqlite3_nif.so for iOS simulator
ld: warning: -undefined dynamic_lookup is deprecated on iOS-simulator
  === Copying priv/repo assets
  === Copying Elixir stdlib
  === Copying EEx stdlib
  === Syncing OTP runtime to /Users/camilo/.mob/runtime/ios-sim
  === Copying Mob logos
  === Spot-check
  ✓ /Users/camilo/.mob/cache/otp-ios-sim-d9045670/calculator/Elixir.Calculator.App.beam
  ✓ /Users/camilo/.mob/cache/otp-ios-sim-d9045670/calculator/Elixir.Calculator.HomeScreen.beam
  === Generating enif_* keep-alive table
  174 enif_* symbols pinned
error: invalid option: -Dproject_swift_sources
error:   access the help menu with 'zig build -h'
error: the following build command failed with exit code 1:
ios/.zig-cache/o/10ad23d224495e444f3e1d6bd7521ad8/build /Users/camilo/.local/share/mise/installs/zig/0.16.0/zig /Users/camilo/.local/share/mise/installs/zig/0.16.0/lib ios ios/.zig-cache /Users/camilo/.cache/zig --seed 0x792f34d2 -Zbb9e8bd190cceb4a binary -Dmob_dir=/Users/camilo/Developer/elixircl/elixir-mobile/modules/calculator/examples/calculator/deps/mob -Dotp_root=/Users/camilo/.mob/cache/otp-ios-sim-d9045670 -Derts_vsn=erts-17.0 -Dsdkroot=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator26.5.sdk -Ddriver_tab=/Users/camilo/Developer/elixircl/elixir-mobile/modules/calculator/examples/calculator/deps/mob/ios/driver_tab_ios.zig -Denif_keepalive=/var/folders/nx/h37qd0kd7d93gy72rhh22bv40000gn/T/mob_ios_sim_3426/enif_keepalive.c -Dproject_ios_dir=/Users/camilo/Developer/elixircl/elixir-mobile/modules/calculator/examples/calculator/ios -Dmodule_name=Calculator -Dproject_swift_sources= -Dproject_root=/Users/camilo/Developer/elixircl/elixir-mobile/modules/calculator/examples/calculator -Dproject_c_nifs= -Dproject_rust_libs=
  ✗ iOS native build failed: zig build binary (iOS sim) exited 1

Native build had failures — see errors above.
Run `mix mob.doctor` to check your environment, or `mix mob.deploy` (without --native) once the issue is fixed.
** (Mix) Native build failed

[clsource]

I asked OpenCode about this but I dont know if this is correct.

• ios/build_device.zig — added option declaration at line 69:

const project_swift_sources = b.option([]const u8, "project_swift_sources", "Comma-separated paths to project Swift sources (from mob.exs :project_swift_sources); empty if none") orelse "";

• Both ios/build.zig and ios/build_device.zig — added consumption of the option in the swiftc step (after the Mob standard .swift files):

    if (project_swift_sources.len > 0) {
        var ps_it = std.mem.splitScalar(u8, project_swift_sources, ',');
        while (ps_it.next()) |ps| {
            if (ps.len > 0) swift_run.addFileArg(.{ .cwd_relative = ps });
        }
    }

Previously build_device.zig had no declaration at all (causing the crash), and both files declared but never used the variable (causing the unused-constant warning).

These flags are passed here

deps/mob_dev/lib/mob_dev/native_build.ex:

• Line 2168 — sim build (build.zig): "-Dproject_swift_sources=#{project_swift_sources}"
• Line 3380 — device build (build_device.zig): "-Dproject_swift_sources=#{project_swift_sources}"
  Both are in the base_args list passed to zig build binary --build-file ios/build.zig (or build_device.zig).

[clsource]

Maybe this is related GenericJam/mob_dev#12

[clsource]

Upon futher investigation I think is was a changed made here https://github.com/GenericJam/mob_new/pull/5/changes
that included that new option. But I was using an old mix mob.new command that it didn't add them.

Recommendations:

• add a check in mob.new command to know if there is a newer version than the current installed. Provide instructions on how to update the command (running again mix archive.install hex mob_new to update it)

• add a mob.new --version option to know the current version installed.

Searching for the current version I had mob_new-0.3.7

cd /Users/camilo/.local/share/mise/installs/elixir/1.20.0-rc.5-otp-29/.mix/archives/mob_new-0.3.7

And the project_swift_sources was addeed in 0.3.8 https://hexdocs.pm/mob_new/changelog.html#0-3-8

I updated the version to the latest 0.3.10 and hopefully it will work now 👍

[clsource]

solved