Add separate lint stage to .travis.yml (#87)

The prevents linting stage from running multiple times in all parallel jobs. We're mostly going to develop with the latest version of Xcode, so we only care about linter and formatter warnings with that version. Thus, the linter stage runs first with the latest version, while actual tests run in parallel jobs of the next "test" stage.

* Travis jobs/stages experiment
* Fix pod lint warnings with Xcode 10.2
* Reorder matrix and jobs in .travis.yml
* Specify jobs/stages with YAML references
* Test .travis.yml without YAML references
* Test stages/jobs one by one
* Add install: skip to stages in .travis.yml
* Update .travis.yml
* Add codecov upload to one of the jobs
* Add back lint stage
* Rename `unit-test` stage to `test`
* Add separate Package.swift for Swift 5.0
* Add explicit top level osx_image to .travis.yml

.travis.yml

@@ -1,14 +1,46 @@
+osx_image: xcode10.2
+language: swift
 
-matrix:
+env:
+  global:
+  - FRAMEWORK_NAME=XMLCoder
+
+jobs:
   include:
-  - osx_image: xcode10
+  - stage: lint
+    osx_image: xcode10.2
     language: swift
-    env: TEST_DEVICE='platform=iOS Simulator,OS=12.0,name=iPhone SE'
-  - osx_image: xcode10.1
+    before_install:
+      - brew update
+      - brew install swiftformat
+      - brew outdated swiftlint || brew upgrade swiftlint
+    script:
+      - swiftformat --lint --verbose .
+      - swiftlint
+      - pod lib lint --verbose
+  - &test
+    stage: test
+    osx_image: xcode10
     language: swift
+    install: skip
+    env: TEST_DEVICE='platform=iOS Simulator,OS=12.0,name=iPhone SE'
+    script:
+      - >
+        xcodebuild test -enableCodeCoverage YES -scheme XMLCoder
+        -sdk iphonesimulator -destination "$TEST_DEVICE" | xcpretty
+      - >
+        xcodebuild test -enableCodeCoverage YES -scheme XMLCoder 
+        -sdk macosx | xcpretty
+      # this runs the tests the second time, but it's the only way to make sure
+      # that `Package.swift` is in a good state and `swift test` can only generate
+      # coverage reports in Swift 5.0, see this issue for more details:
+      # https://github.com/apple/swift-package-manager/pull/1787
+      - swift test
+  - <<: *test
+    osx_image: xcode10.1
     env: TEST_DEVICE='platform=iOS Simulator,OS=12.1,name=iPhone SE'
-  - osx_image: xcode10.2
-    language: swift
+  - <<: *test
+    osx_image: xcode10.2
     env: TEST_DEVICE='platform=iOS Simulator,OS=12.2,name=iPhone SE'
     after_success:
     - bash <(curl -s https://codecov.io/bash)
@@ -26,33 +58,5 @@ matrix:
         repo: MaxDesiatov/XMLCoder
         tags: true
 
-env:
-  global:
-  - FRAMEWORK_NAME=XMLCoder
-before_install:
-- gem install cocoapods --pre # Since Travis is not always on latest version
-- brew update
-- brew install swiftformat
-- brew outdated swiftlint || brew upgrade swiftlint
-script:
-- swiftformat --lint --verbose .
-- swiftlint
-- pod lib lint --verbose
-- >
-  xcodebuild test -enableCodeCoverage YES -scheme XMLCoder
-  -sdk iphonesimulator -destination "$TEST_DEVICE" | xcpretty
-- xcodebuild test -enableCodeCoverage YES -scheme XMLCoder -sdk macosx | xcpretty
-
-# this runs the tests the second time, but it's the only way to make sure
-# that `Package.swift` is in a good state and `swift test` can only generate
-# coverage reports in Swift 5.0, see this issue for more details:
-# https://github.com/apple/swift-package-manager/pull/1787
-- swift test
-
 # this is commented because installing Jazzy on Travis doesn't work ¯\_(ツ)_/¯ 
 # - ./docs.sh
-
-# jobs:
-#   include:
-#   - stage: deploy
-#     osx_image: xcode10.1

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:4.2
+// swift-tools-version:5.0
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
@@ -27,6 +27,5 @@ let package = Package(
             name: "XMLCoderTests",
             dependencies: ["XMLCoder"]
         ),
-    ],
-    swiftLanguageVersions: [.v4_2, .version("5")]
+    ]
 )

Package@swift-4.2.swift

@@ -0,0 +1,31 @@
+// swift-tools-version:4.2
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "XMLCoder",
+    products: [
+        // Products define the executables and libraries produced by a package, and make them visible to other packages.
+        .library(
+            name: "XMLCoder",
+            targets: ["XMLCoder"]
+        ),
+    ],
+    dependencies: [
+        // Dependencies declare other packages that this package depends on.
+        // .package(url: /* package url */, from: "1.0.0"),
+    ],
+    targets: [
+        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
+        // Targets can depend on other targets in this package, and on products in packages which this package depends on.
+        .target(
+            name: "XMLCoder",
+            dependencies: []
+        ),
+        .testTarget(
+            name: "XMLCoderTests",
+            dependencies: ["XMLCoder"]
+        ),
+    ]
+)

Sources/XMLCoder/Auxiliaries/XMLStackParser.swift

@@ -72,8 +72,13 @@ class XMLStackParser: NSObject {
             upperBoundIndex = errorPosition + offset
         }
 
+        #if compiler(>=5.0)
+        let lowerBound = String.Index(utf16Offset: lowerBoundIndex, in: string)
+        let upperBound = String.Index(utf16Offset: upperBoundIndex, in: string)
+        #else
         let lowerBound = String.Index(encodedOffset: lowerBoundIndex)
         let upperBound = String.Index(encodedOffset: upperBoundIndex)
+        #endif
 
         let context = string[lowerBound..<upperBound]