WIP Initial commit

This creates a Swift package with an example app, linting and formatting
commands, CI pipeline, README, and contributing guidelines.

In the absence of guidance or data about which minimum Swift version to
use, I decided to use the latest release at time of writing (5.10). We
can revisit this later if need be.

The SwiftLint rules are taken from our Asset Tracking repo at commit
b39e5187. They seemed like a good starting point (I had previously done
some thinking about these rules in [1]), and we can tweak them as
needed. I’ve enabled the private_swiftui_state rule (seems useful) and
also inverted its default trailing comma rule (for compatibility with
SwiftFormat).

Upon realising that SwiftLint and SwiftFormat have clashing opinions on
trailing commas, I worried that there might turn out to be other clashes
between the two. So I then hoped that we could get away with just using
SwiftLint, which does have some style rules. But it doesn’t enforce some
basic things like indentation. I hope that there aren’t further clashes
between the two tools, but we won’t find out until we write more code.

We use Mint to run SwiftLint and SwiftFormat. This allows us to lock
their versions, which we can’t do with Homebrew. It’s unfortunate that
for some reason SwiftLint takes an eternity to build using Mint, but
it’s a one-time thing per developer. I originally ran these tools as
Swift package plugins, but SwiftLint’s plugin was crashing when run in
Xcode 16 beta, hence the switch to Mint. Maybe we can switch back
sometime.

The build scripts used by CI, as well as one of the linting steps, are
implemented as a Swift command-line tool. Hopefully we’ll find this
easier to maintain and modify than a set of Bash scripts.

TODO fix-then-check?

[1] ably/ably-asset-tracking-swift#629

.github/workflows/check.yaml

@@ -0,0 +1,114 @@
+name: Check
+
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+      - main
+jobs:
+  lint:
+    runs-on: macos-latest
+
+    # From actions/cache documentation linked to below
+    env:
+      MINT_PATH: .mint/lib
+      MINT_LINK_PATH: .mint/bin
+
+    steps:
+      - uses: actions/checkout@v4
+
+      # We use caching for Mint because at the time of writing SwiftLint took about 5 minutes to build in CI, which is unacceptably slow.
+      # https://github.com/actions/cache/blob/40c3b67b2955d93d83b27ed164edd0756bc24049/examples.md#swift---mint
+      - uses: actions/cache@v4
+        with:
+          path: .mint
+          key: ${{ runner.os }}-mint-${{ hashFiles('**/Mintfile') }}
+          restore-keys: |
+            ${{ runner.os }}-mint-
+
+      - run: npm ci
+      - run: brew install mint
+      - run: mint bootstrap
+
+      - run: script/lint/check
+
+  generate-matrices:
+    runs-on: macos-latest
+    outputs:
+      matrix: ${{ steps.generation-step.outputs.matrix }}
+    steps:
+      - uses: actions/checkout@v4
+      - id: generation-step
+        run: swift run BuildTool generate-matrices >> $GITHUB_OUTPUT
+
+  check-spm:
+    name: SPM (Xcode ${{ matrix.tooling.xcodeVersion }}, Swift ${{ matrix.tooling.swiftVersion }})
+    runs-on: macos-latest
+    needs: generate-matrices
+    strategy:
+      fail-fast: false
+      matrix: ${{ fromJson(needs.generate-matrices.outputs.matrix).withoutPlatform }}
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: ${{ matrix.tooling.xcodeVersion }}
+
+      # https://forums.swift.org/t/warnings-as-errors-for-libraries-frameworks/58393/2
+      - run: swift build -Xswiftc -warnings-as-errors -Xswiftc -swift-version -Xswiftc ${{ matrix.tooling.swiftVersion }}
+      - run: swift test -Xswiftc -warnings-as-errors -Xswiftc -swift-version -Xswiftc ${{ matrix.tooling.swiftVersion }}
+
+  check-xcode:
+    name: Xcode, ${{matrix.platform}} (Xcode ${{ matrix.tooling.xcodeVersion }}, Swift ${{ matrix.tooling.swiftVersion }})
+    runs-on: macos-latest
+    needs: generate-matrices
+
+    strategy:
+      fail-fast: false
+      matrix: ${{ fromJson(needs.generate-matrices.outputs.matrix).withPlatform }}
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: ${{ matrix.tooling.xcodeVersion }}
+
+      - name: Build and run tests
+        run: swift run BuildTool build-and-test-library --platform ${{ matrix.platform }} --swift-version ${{ matrix.tooling.swiftVersion }}
+
+  check-example-app:
+    name: Example app, ${{matrix.platform}} (Xcode ${{ matrix.tooling.xcodeVersion }}, Swift ${{ matrix.tooling.swiftVersion }})
+    runs-on: macos-latest
+    needs: generate-matrices
+
+    strategy:
+      fail-fast: false
+      matrix: ${{ fromJson(needs.generate-matrices.outputs.matrix).withPlatform }}
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: ${{ matrix.tooling.xcodeVersion }}
+
+      - name: Build example app
+        run: swift run BuildTool build-example-app --platform ${{ matrix.platform }} --swift-version ${{ matrix.tooling.swiftVersion }}
+
+  # We use this job as a marker that all of the required checks have completed.
+  # This allows us to configure a single required status check in our branch
+  # protection rules instead of having to type loads of different check names
+  # into the branch protection web UI (and keep this list up to date as we
+  # tweak the matrices).
+  all-checks-completed:
+    runs-on: ubuntu-latest
+    needs:
+      - lint
+      - check-spm
+      - check-xcode
+      - check-example-app
+
+    steps:
+      - name: No-op
+        run: "true"

.gitignore

@@ -0,0 +1,13 @@
+# Start of .gitignore created by Swift Package Manager
+.DS_Store
+/.build
+/Packages
+xcuserdata/
+DerivedData/
+.swiftpm/configuration/registries.json
+.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
+.netrc
+# End of .gitignore created by Swift Package Manager
+
+/node_modules
+/.mint

.prettierignore

@@ -0,0 +1,2 @@
+# Don’t try and format the asset catalogue JSON files, which are managed by Xcode
+*.xcassets/

.prettierrc

@@ -0,0 +1 @@
+{}

.swift-version

@@ -0,0 +1 @@
+5.10

.swiftlint.yml

@@ -0,0 +1,102 @@
+excluded:
+  - .build
+
+strict: true
+
+disabled_rules:
+  # All of the default rules of type "metrics". We have no reason to believe that the arbitrary defaults picked by SwiftLint are helpful.
+  - cyclomatic_complexity
+  - file_length
+  - function_body_length
+  - function_parameter_count
+  - large_tuple
+  - line_length
+  - nesting
+  - type_body_length
+
+  # Rules of type "lint" that we’ve decided we don’t want:
+  - todo # We frequently use TODOs accompanied by a GitHub issue reference
+
+opt_in_rules:
+  # All of the opt-in rules of type "performance":
+  - contains_over_filter_count
+  - contains_over_filter_is_empty
+  - contains_over_first_not_nil
+  - contains_over_range_nil_comparison
+  - empty_collection_literal
+  - empty_count
+  - empty_string
+  - first_where
+  - flatmap_over_map_reduce
+  - last_where
+  - reduce_into
+  - sorted_first_last
+
+  # Opt-in rules of type "style" that we’ve decided we want:
+  - attributes
+  - closure_end_indentation
+  - closure_spacing
+  - collection_alignment
+  - comma_inheritance
+  - conditional_returns_on_newline
+  - file_header
+  - implicit_return
+  - literal_expression_end_indentation
+  - modifier_order
+  - multiline_arguments
+  - multiline_arguments_brackets
+  - multiline_function_chains
+  - multiline_literal_brackets
+  - multiline_parameters
+  - multiline_parameters_brackets
+  - operator_usage_whitespace
+  - prefer_self_type_over_type_of_self
+  - self_binding
+  - single_test_class
+  - sorted_imports
+  - switch_case_on_newline
+  - trailing_closure
+  - trailing_newline
+  - unneeded_parentheses_in_closure_argument
+  - vertical_parameter_alignment_on_call
+  - vertical_whitespace_closing_braces
+  - vertical_whitespace_opening_braces
+
+  # Opt-in rules of type "idiomatic" that we’ve decided we want:
+  - anonymous_argument_in_multiline_closure
+  - convenience_type
+  - fallthrough
+  - fatal_error_message
+  - pattern_matching_keywords
+  - redundant_type_annotation
+  - shorthand_optional_binding
+  - static_operator
+  - toggle_bool
+  - xct_specific_matcher
+
+  # Opt-in rules of type "lint" that we’ve decided we want:
+  - array_init
+  - empty_xctest_method
+  - missing_docs
+  - override_in_extension
+  - yoda_condition
+  - private_swiftui_state
+
+file_header:
+  # Comments, except for the required and standard ones at the top of a Package.swift file
+  forbidden_pattern: //(?! (swift-tools-version:|The swift-tools-version declares the minimum version of Swift required to build this package\.))
+
+identifier_name:
+  &no_length_checks # We disable the length checks, for the same reason we disable the rules of type "metrics".
+  min_length:
+    warning: 1
+  max_length:
+    warning: 10000
+
+type_name: *no_length_checks
+
+generic_type_name: *no_length_checks
+
+# For compatibility with SwiftFormat
+trailing_comma:
+  mandatory_comma: true

.swiftpm/configuration/Package.resolved

@@ -0,0 +1,42 @@
+{
+  "originHash" : "9d852a8f936d58dcf5f543508d205baeff66d9e230197f5987ee4f89aa7b1bf1",
+  "pins" : [
+    {
+      "identity" : "ably-cocoa",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/ably/ably-cocoa",
+      "state" : {
+        "revision" : "7f639c609e50053abd4590f34333f9472645558a",
+        "version" : "1.2.33"
+      }
+    },
+    {
+      "identity" : "delta-codec-cocoa",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/ably/delta-codec-cocoa",
+      "state" : {
+        "revision" : "3ee62ea40a63996b55818d44b3f0e56d8753be88",
+        "version" : "1.3.3"
+      }
+    },
+    {
+      "identity" : "msgpack-objective-c",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/rvi/msgpack-objective-C",
+      "state" : {
+        "revision" : "3e36b48e04ecd756cb927bd5f5b9bf6d45e475f9",
+        "version" : "0.4.0"
+      }
+    },
+    {
+      "identity" : "swift-argument-parser",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-argument-parser",
+      "state" : {
+        "revision" : "41982a3656a71c768319979febd796c6fd111d5c",
+        "version" : "1.5.0"
+      }
+    }
+  ],
+  "version" : 3
+}

.swiftpm/xcode/package.xcworkspace/xcshareddata/WorkspaceSettings.xcsettings

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEWorkspaceSharedSettings_AutocreateContextsIfNeeded</key>
+	<true/>
+</dict>
+</plist>

.swiftpm/xcode/xcshareddata/xcschemes/AblyChat.xcscheme

@@ -0,0 +1,79 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "1540"
+   version = "1.7">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES"
+      buildArchitectures = "Automatic">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "AblyChat"
+               BuildableName = "AblyChat"
+               BlueprintName = "AblyChat"
+               ReferencedContainer = "container:">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      shouldAutocreateTestPlan = "YES">
+      <Testables>
+         <TestableReference
+            skipped = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "AblyChatTests"
+               BuildableName = "AblyChatTests"
+               BlueprintName = "AblyChatTests"
+               ReferencedContainer = "container:">
+            </BuildableReference>
+         </TestableReference>
+      </Testables>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "AblyChat"
+            BuildableName = "AblyChat"
+            BlueprintName = "AblyChat"
+            ReferencedContainer = "container:">
+         </BuildableReference>
+      </MacroExpansion>
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>

AblyChat.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>