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.github/workflows/ci.yaml vendored Normal file
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name: CI
on: [push, pull_request]
jobs:
unit-test:
runs-on: ubuntu-latest
container: swift:5.2
steps:
- name: Checkout
uses: actions/checkout@v1
- name: Build & Test
run: swift test -c release --enable-test-discovery

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.DS_Store
/.build
/Packages
/*.xcodeproj
xcuserdata/
.swiftpm

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.swiftformat Normal file
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# file options
--swiftversion 5.2
--exclude .build
--exclude UseCases/.build
# format options
--ifdef no-indent
--patternlet inline
--self insert
--stripunusedargs closure-only
--wraparguments before-first
# rules
--disable blankLinesAroundMark

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Package.swift Normal file
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// swift-tools-version:5.2
import PackageDescription
let package = Package(
name: "gsoc-swift-baggage-context",
products: [
.library(name: "Baggage", targets: ["Baggage"])
],
targets: [
.target(
name: "Baggage",
dependencies: []
),
.testTarget(
name: "BaggageTests",
dependencies: [
"Baggage"
]
)
]
)

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README.md Normal file
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# Baggage Context
[![Swift 5.2](https://img.shields.io/badge/Swift-5.2-ED523F.svg?style=flat)](https://swift.org/download/)
[![CI](https://github.com/slashmo/gsoc-swift-baggage-context/workflows/CI/badge.svg)](https://github.com/slashmo/gsoc-swift-baggage-context/actions?query=workflow%3ACI)
`BaggageContext` originated in [this repo](https://github.com/slashmo/gsoc-swift-tracing), but had to be factored out so that we can depend on it in our [NIO fork](https://github.com/slashmo/swift-nio).
## Contributing
Please make sure to run the `./scripts/sanity.sh` script when contributing, it checks formatting and similar things.
You can make ensure it always is run and passes before you push by installing a pre-push hook with git:
```
echo './scripts/sanity.sh' > .git/hooks/pre-push
```

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/// A `BaggageContext` is a heterogeneous storage type with value semantics for keyed values in a type-safe
/// fashion. Its values are uniquely identified via `BaggageContextKey`s. These keys also dictate the type of
/// value allowed for a specific key-value pair through their associated type `Value`.
///
/// ## Subscript access
/// You may access the stored values by subscripting with a key type conforming to `BaggageContextKey`.
///
/// enum TestIDKey: BaggageContextKey {
/// typealias Value = String
/// }
///
/// var baggage = BaggageContext()
/// // set a new value
/// baggage[TestIDKey.self] = "abc"
/// // retrieve a stored value
/// baggage[TestIDKey.self] ?? "default"
/// // remove a stored value
/// baggage[TestIDKey.self] = nil
///
/// ## Convenience extensions
///
/// Libraries may also want to provide an extension, offering the values that users are expected to reach for
/// using the following pattern:
///
/// extension BaggageContext {
/// var testID: TestIDKey.Value {
/// get {
/// self[TestIDKey.self]
/// } set {
/// self[TestIDKey.self] = newValue
/// }
/// }
/// }
public struct BaggageContext {
private var _storage = [AnyBaggageContextKey: ValueContainer]()
/// Create an empty `BaggageContext`.
public init() {}
public subscript<Key: BaggageContextKey>(_ key: Key.Type) -> Key.Value? {
get {
self._storage[AnyBaggageContextKey(key)]?.forceUnwrap(key)
} set {
self._storage[AnyBaggageContextKey(key)] = newValue.map {
ValueContainer(value: $0)
}
}
}
public var baggageItems: [AnyBaggageContextKey: Any] {
// TODO: key may not be unique
self._storage.reduce(into: [:]) {
$0[$1.key] = $1.value.value
}
}
private struct ValueContainer {
let value: Any
func forceUnwrap<Key: BaggageContextKey>(_ key: Key.Type) -> Key.Value {
self.value as! Key.Value
}
}
}
extension BaggageContext: CustomStringConvertible {
public var description: String {
"\(Self.self)(keys: \(self._storage.map(\.key.name)))"
}
}
/// `BaggageContextKey`s are used as keys in a `BaggageContext`. Their associated type `Value` gurantees type-safety.
/// To give your `BaggageContextKey` an explicit name you may override the `name` property.
public protocol BaggageContextKey {
/// The type of `Value` uniquely identified by this key.
associatedtype Value
/// The human-readable name of this key. Defaults to `nil`.
static var name: String? { get }
}
extension BaggageContextKey {
public static var name: String? { nil }
}
public struct AnyBaggageContextKey {
public let keyType: Any.Type
private let _name: String?
/// A human-readable String representation of the underlying key.
/// If no explicit name has been set on the wrapped key the type name is used.
public var name: String {
self._name ?? String(describing: self.keyType.self)
}
public init<Key>(_ keyType: Key.Type) where Key: BaggageContextKey {
self.keyType = keyType
self._name = keyType.name
}
}
extension AnyBaggageContextKey: Hashable {
public static func == (lhs: AnyBaggageContextKey, rhs: AnyBaggageContextKey) -> Bool {
ObjectIdentifier(lhs.keyType) == ObjectIdentifier(rhs.keyType)
}
public func hash(into hasher: inout Hasher) {
hasher.combine(ObjectIdentifier(self.keyType))
}
}

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Tests/BaggageTests/BaggageContextTests.swift Normal file
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import Baggage
import XCTest
final class BaggageContextTests: XCTestCase {
func testSubscriptAccess() {
let testID = 42
var baggage = BaggageContext()
XCTAssertNil(baggage[TestIDKey.self])
baggage[TestIDKey.self] = testID
XCTAssertEqual(baggage[TestIDKey], testID)
baggage[TestIDKey.self] = nil
XCTAssertNil(baggage[TestIDKey.self])
}
func testRecommendedConvenienceExtension() {
let testID = 42
var baggage = BaggageContext()
XCTAssertNil(baggage.testID)
baggage.testID = testID
XCTAssertEqual(baggage.testID, testID)
baggage[TestIDKey.self] = nil
XCTAssertNil(baggage.testID)
}
func testEmptyBaggageDescription() {
XCTAssertEqual(String(describing: BaggageContext()), "BaggageContext(keys: [])")
}
func testSingleKeyBaggageDescription() {
var baggage = BaggageContext()
baggage.testID = 42
XCTAssertEqual(String(describing: baggage), #"BaggageContext(keys: ["TestIDKey"])"#)
}
func testMultiKeysBaggageDescription() {
var baggage = BaggageContext()
baggage.testID = 42
baggage[SecondTestIDKey.self] = "test"
let description = String(describing: baggage)
XCTAssert(description.starts(with: "BaggageContext(keys: ["))
// use contains instead of `XCTAssertEqual` because the order is non-predictable (Dictionary)
XCTAssert(description.contains("TestIDKey"))
XCTAssert(description.contains("ExplicitKeyName"))
print(description.reversed().starts(with: "])"))
}
}
private enum TestIDKey: BaggageContextKey {
typealias Value = Int
}
private extension BaggageContext {
var testID: Int? {
get {
self[TestIDKey.self]
} set {
self[TestIDKey.self] = newValue
}
}
}
private enum SecondTestIDKey: BaggageContextKey {
typealias Value = String
static let name: String? = "ExplicitKeyName"
}

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scripts/sanity.sh Executable file
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#!/bin/bash
set -eu
here="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
# bash $here/validate_license_header.sh
bash $here/validate_format.sh

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#!/bin/bash
set -u
# verify that swiftformat is on the PATH
command -v swiftformat >/dev/null 2>&1 || { echo >&2 "'swiftformat' could not be found. Please ensure it is installed and on the PATH."; exit 1; }
printf "=> Checking format\n"
FIRST_OUT="$(git status --porcelain)"
# swiftformat does not scale so we loop ourselves
shopt -u dotglob
find Sources/* Tests/* -type d | while IFS= read -r d; do
printf " * checking $d... "
out=$(swiftformat $d 2>&1)
SECOND_OUT="$(git status --porcelain)"
if [[ "$out" == *"error"*] && ["$out" != "*No eligible files" ]]; then
printf "\033[0;31merror!\033[0m\n"
echo $out
exit 1
fi
if [[ "$FIRST_OUT" != "$SECOND_OUT" ]]; then
printf "\033[0;31mformatting issues!\033[0m\n"
git --no-pager diff
exit 1
fi
printf "\033[0;32mokay.\033[0m\n"
done