[POC] Script to compare API of 2 versions of the SDK

compare-api.sh

@@ -0,0 +1,102 @@
+#!/bin/bash -eu
+
+# This scripts tries to replicate what `swift package diagnose-api-breaking-changes` does but for an iOS SDK
+#
+# I haven't found a way to do this with `swift package diagnose-api-breaking-changes` so I'm doing it manually
+#
+# Closest I've found is:
+# ```
+# swift package \
+#   --sdk "$(xcrun --sdk iphoneos --show-sdk-path)" \
+#   --triple arm64-apple-ios \
+#   diagnose-api-breaking-changes 2.1.0
+# ```
+# but it doesn't work as well:
+# - If I point to `2.1.0`, it generates errors during compilation about `type 'Bundle' has no member 'module'`. I think that might be because the swift-tools-version have changed since 2.1.0 though
+# - If I point to `3.2.0-rc.1`, it succeeds to compile... but generates empty `.build//arm64-apple-ios/apidiff/*/*/json` files, which makes the `swift api-digester` command fail with "Unable to parse empty data."
+#
+# So I'm working around by doing the intermediate steps manually compiling with `xcodebuild` then using `swift api-digester` instead.
+
+
+# Prints a blue header (level 1)
+function h1() {
+  printf '\033[1;34m======================================================\033[0m\n'
+  printf '\033[1;34m| %-50s |\033[0m\n' "$1"
+  printf '\033[1;34m======================================================\033[0m\n'
+}
+
+# Prints a blue header (level 2)
+function h2() {
+  printf '\033[1;34m------------------------------------------------------\033[0m\n'
+  printf '\033[1;34m%s\033[0m\n' "$1"
+  printf '\033[1;34m------------------------------------------------------\033[0m\n'
+}
+
+# Build the SDK (from current branch) in .build/
+#
+function build_sdk() {
+  h2 "Building SDK"
+  xcodebuild clean build \
+      -scheme "Gravatar-Package" \
+      -derivedDataPath .build \
+      -sdk "$(xcrun --sdk iphoneos --show-sdk-path)" \
+      -destination "generic/platform=iOS" \
+      BUILD_LIBRARY_FOR_DISTRIBUTION=YES | xcpretty
+}
+
+# Use api-digester to dump the SDK API to a JSON file
+#
+# $1: output file
+#
+function dump_sdk_api() {
+  h2 "Dumping SDK API"
+  swift api-digester -dump-sdk \
+    -module Gravatar \
+    -o "$1" \
+    -I .build/Build/Products/Debug-iphoneos \
+    -sdk "`xcrun --sdk iphoneos --show-sdk-path`" \
+    -target "arm64-apple-ios"
+  echo "==> Generated API JSON to $1"
+}
+
+# Generate the API JSON for a given branch/treeish
+#
+# Checks out the branch, then calls `build_sdk`, then `dump_sdk_api`
+#
+# $1: branch/treeish to build + dump the API for
+#
+function generate_api_for_branch() {
+  h1 "Generating API JSON for $1"
+  git checkout "$1"
+  build_sdk
+  dump_sdk_api ".build/api-${1/\//-}.json"
+}
+
+# Compare the API of two branches/treeishs
+#
+# Calls `generate_api_for_branch` for both branches, then `swift api-digester` to compare the APIs
+#
+# $1: old branch/treeish to compare against
+# $2: new branch/treeish to compare against, or current branch if not provided
+#
+function compare_api() {
+  local current_branch
+  current_branch=$(git rev-parse --abbrev-ref HEAD)
+
+  local old_branch="$1"
+  local new_branch="${2:-$current_branch}"
+
+  generate_api_for_branch "$old_branch"
+  git restore Package.resolved
+  generate_api_for_branch "$new_branch"
+
+  git checkout "$current_branch"
+
+  h1 "Diagnosing API differences"
+  swift api-digester -diagnose-sdk \
+    --input-paths ".build/api-${old_branch/\//-}.json" \
+    --input-paths ".build/api-${new_branch/\//-}.json" \
+    2>&1 | sed $'s|^/\\*.*\\*/|\x1b[1;33m&\x1b[0m|' # the use of `sed` is to colorize the diff output
+}
+
+compare_api "$@"