Make examples standalone packages (#2067)

Motivation:

Standalone packages for examples are an easier on-ramp for newcomers as
they only see the details they care about and it can act as a starting
point which they can develop from.

Modifications:

- Turn each example into a standalone package and add a README to each
- Update the generate and fetch scripts and re-run them

Result:

Better examples

---------

Co-authored-by: Gus Cairo <[email protected]>

Author: glbrntt

.github/workflows/ci.yaml

@@ -65,3 +65,18 @@ jobs:
       working-directory: "./IntegrationTests/Benchmarks"
       run: swift package benchmark baseline check --no-progress --check-absolute-path Thresholds/${{ matrix.swift-version }}/
       timeout-minutes: 20
+  examples:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - image: swiftlang/swift:nightly-jammy
+          - image: swift:6.0-jammy
+    name: Build examples using ${{ matrix.image }}
+    runs-on: ubuntu-latest
+    container:
+      image: ${{ matrix.image }}
+    steps:
+    - uses: actions/checkout@v4
+    - name: Build examples
+      run: ./dev/build-examples.sh

Examples/echo/.gitignore

@@ -0,0 +1,8 @@
+.DS_Store
+/.build
+/Packages
+xcuserdata/
+DerivedData/
+.swiftpm/configuration/registries.json
+.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
+.netrc

Examples/echo/Package.swift

@@ -0,0 +1,38 @@
+// swift-tools-version:6.0
+/*
+ * Copyright 2024, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import PackageDescription
+
+let package = Package(
+  name: "echo",
+  platforms: [.macOS("15.0")],
+  dependencies: [
+    .package(url: "https://github.com/grpc/grpc-swift-protobuf", branch: "main"),
+    .package(url: "https://github.com/grpc/grpc-swift-nio-transport", branch: "main"),
+    .package(url: "https://github.com/apple/swift-argument-parser", from: "1.5.0"),
+  ],
+  targets: [
+    .executableTarget(
+      name: "echo",
+      dependencies: [
+        .product(name: "GRPCNIOTransportHTTP2", package: "grpc-swift-nio-transport"),
+        .product(name: "GRPCProtobuf", package: "grpc-swift-protobuf"),
+        .product(name: "ArgumentParser", package: "swift-argument-parser"),
+      ]
+    )
+  ]
+)

Examples/echo/README.md

@@ -0,0 +1,46 @@
+# Echo
+
+This example demonstrates all four RPC types using a simple 'echo' service and
+client and the Swift NIO based HTTP/2 transport.
+
+## Overview
+
+An "echo" command line tool that uses generated stubs for an 'echo' service
+which allows you to start a server and to make requests against it for each of
+the four RPC types.
+
+The tool uses the [SwiftNIO](https://github.com/grpc/grpc-swift-nio-transport)
+HTTP/2 transport.
+
+## Usage
+
+Build and run the server using the CLI:
+
+```console
+$ swift run echo serve
+Echo listening on [ipv4]127.0.0.1:1234
+```
+
+Use the CLI to make a unary 'Get' request against it:
+
+```console
+$ swift run echo get --message "Hello"
+get → Hello
+get ← Hello
+```
+
+Use the CLI to make a bidirectional streaming 'Update' request:
+
+```console
+$ swift run echo update --message "Hello World"
+update → Hello
+update → World
+update ← Hello
+update ← World
+```
+
+Get help with the CLI by running:
+
+```console
+$ swift run echo --help
+```

Examples/v2/echo/Echo.swift renamed to Examples/echo/Sources/Echo.swift

@@ -17,7 +17,6 @@
 import ArgumentParser
 
 @main
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 struct Echo: AsyncParsableCommand {
   static let configuration = CommandConfiguration(
     commandName: "echo",

Examples/v2/echo/Generated/echo.grpc.swift renamed to Examples/echo/Sources/Generated/echo.grpc.swift

@@ -15,7 +15,7 @@
  */
 
 import ArgumentParser
-import GRPCHTTP2Core
+import GRPCNIOTransportHTTP2
 
 struct ClientArguments: ParsableArguments {
   @Option(help: "The server's listening port")

Examples/v2/echo/Generated/echo.pb.swift renamed to Examples/echo/Sources/Generated/echo.pb.swift

@@ -16,10 +16,8 @@
 
 import ArgumentParser
 import GRPCCore
-import GRPCHTTP2Core
-import GRPCHTTP2TransportNIOPosix
+import GRPCNIOTransportHTTP2
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 struct Collect: AsyncParsableCommand {
   static let configuration = CommandConfiguration(
     abstract: "Makes a client streaming RPC to the echo server."

Examples/v2/echo/Subcommands/ClientArguments.swift renamed to Examples/echo/Sources/Subcommands/ClientArguments.swift

@@ -16,10 +16,8 @@
 
 import ArgumentParser
 import GRPCCore
-import GRPCHTTP2Core
-import GRPCHTTP2TransportNIOPosix
+import GRPCNIOTransportHTTP2
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 struct Expand: AsyncParsableCommand {
   static let configuration = CommandConfiguration(
     abstract: "Makes a server streaming RPC to the echo server."