Build example projects (#76)

Build the Examples in CI.

### Motivation:

`swift-metrics-extras` now has an `Example/ServiceIntegration`, which
depends on the package, but is not verified in the CI.

### Modifications:

- `Scripts/test-examples.sh` added (inspired by the
[`swift-configuration/Scripts/test-examples.sh`](https://github.com/apple/swift-configuration/blob/main/Scripts/test-examples.sh),
but the structure is different and this one is more simple).
- `pull_request` and `main` workflows use shared
`apple/swift-nio/.github/workflows/swift_test_matrix.yml@main` to run
the script.

### Result:

`Example/ServiceIntegration` is being built in CI on Linux

.github/workflows/main.yml

@@ -34,3 +34,32 @@ jobs:
   release-builds:
     name: Release builds
     uses: apple/swift-nio/.github/workflows/release_builds.yml@main
+
+  construct-example-packages-matrix:
+    name: Construct example packages matrix
+    runs-on: ubuntu-latest
+    outputs:
+      example-packages-matrix: '${{ steps.generate-matrix.outputs.example-packages-matrix }}'
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - id: generate-matrix
+        run: echo "example-packages-matrix=$(curl -s https://raw.githubusercontent.com/apple/swift-nio/main/scripts/generate_matrix.sh | bash)" >> "$GITHUB_OUTPUT"
+        env:
+          MATRIX_LINUX_SETUP_COMMAND: git config --global --add safe.directory /swift-metrics-extras
+          MATRIX_LINUX_COMMAND: ./Scripts/test-examples.sh
+          MATRIX_LINUX_5_10_ENABLED: false
+          MATRIX_LINUX_6_0_ENABLED: false
+          MATRIX_LINUX_6_1_ENABLED: false
+          MATRIX_LINUX_NIGHTLY_NEXT_ENABLED: false
+          MATRIX_LINUX_NIGHTLY_MAIN_ENABLED: false
+
+  example-packages:
+    name: Example packages
+    needs: construct-example-packages-matrix
+    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@main
+    with:
+      name: "Example packages"
+      matrix_string: '${{ needs.construct-example-packages-matrix.outputs.example-packages-matrix }}'

.github/workflows/pull_request.yml

@@ -38,3 +38,32 @@ jobs:
   release-builds:
     name: Release builds
     uses: apple/swift-nio/.github/workflows/release_builds.yml@main
+
+  construct-example-packages-matrix:
+    name: Construct example packages matrix
+    runs-on: ubuntu-latest
+    outputs:
+      example-packages-matrix: '${{ steps.generate-matrix.outputs.example-packages-matrix }}'
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - id: generate-matrix
+        run: echo "example-packages-matrix=$(curl -s https://raw.githubusercontent.com/apple/swift-nio/main/scripts/generate_matrix.sh | bash)" >> "$GITHUB_OUTPUT"
+        env:
+          MATRIX_LINUX_SETUP_COMMAND: git config --global --add safe.directory /swift-metrics-extras
+          MATRIX_LINUX_COMMAND: ./Scripts/test-examples.sh
+          MATRIX_LINUX_5_10_ENABLED: false
+          MATRIX_LINUX_6_0_ENABLED: false
+          MATRIX_LINUX_6_1_ENABLED: false
+          MATRIX_LINUX_NIGHTLY_NEXT_ENABLED: false
+          MATRIX_LINUX_NIGHTLY_MAIN_ENABLED: false
+
+  example-packages:
+    name: Build Examples
+    needs: construct-example-packages-matrix
+    uses: apple/swift-nio/.github/workflows/swift_test_matrix.yml@main
+    with:
+      name: "Example packages"
+      matrix_string: '${{ needs.construct-example-packages-matrix.outputs.example-packages-matrix }}'

.licenseignore

@@ -33,3 +33,4 @@ Dockerfile
 Snippets/*
 dev/git.commit.template
 .unacceptablelanguageignore
+Scripts/*

Scripts/test-examples.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+set -euo pipefail
+
+log() { printf -- "** %s\n" "$*" >&2; }
+error() { printf -- "** ERROR: %s\n" "$*" >&2; }
+fatal() { error "$@"; exit 1; }
+
+log "Checking required executables..."
+SWIFT_BIN=${SWIFT_BIN:-$(command -v swift || xcrun -f swift)} || fatal "SWIFT_BIN unset and no swift on PATH"
+
+CURRENT_SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+REPO_ROOT="$(git -C "${CURRENT_SCRIPT_DIR}" rev-parse --show-toplevel)"
+PACKAGE_NAME=$(basename "$REPO_ROOT")
+TMP_DIR=$(/usr/bin/mktemp -d -p "${TMPDIR-/tmp}" "$(basename "$0").XXXXXXXXXX")
+WORK_DIR="$TMP_DIR/$PACKAGE_NAME"
+/bin/mkdir -p "$WORK_DIR"
+
+git archive HEAD "${REPO_ROOT}" --format tar | tar -C "${WORK_DIR}" -xvf-
+
+EXAMPLES_PATH="$WORK_DIR/Examples"
+for EXAMPLE_PACKAGE_PATH in $(find "${EXAMPLES_PATH}" -maxdepth 2 -name Package.swift -type f -print0 | xargs -0 dirname | sort); do
+    EXAMPLE_PACKAGE_NAME=$(basename "$EXAMPLE_PACKAGE_PATH")
+    log "Building example package: ${EXAMPLE_PACKAGE_NAME}"
+    "${SWIFT_BIN}" build --build-tests \
+        --package-path "${EXAMPLE_PACKAGE_PATH}" \
+        --skip-update
+    log "✅ Successfully built the example package ${EXAMPLE_PACKAGE_NAME}."
+
+    if [ -d "${EXAMPLE_PACKAGE_PATH}/Tests" ]; then
+        log "Running tests for example package: ${EXAMPLE_PACKAGE_NAME}"
+        "${SWIFT_BIN}" test \
+            --package-path "${EXAMPLE_PACKAGE_PATH}" \
+            --skip-update
+        log "✅ Passed the tests for the example package ${EXAMPLE_PACKAGE_NAME}."
+    fi
+done