Add apidiff script to check go signature changes

Signed-off-by: Davanum Srinivas <davanum@gmail.com>

.github/workflows/test.yml

@@ -30,3 +30,27 @@ jobs:
           docker run --rm -v `pwd`:/go/src/k8s.io/klog -w /go/src/k8s.io/klog \
             golangci/golangci-lint:v1.23.8 golangci-lint run --disable-all -v \
             -E govet -E misspell -E gofmt -E ineffassign -E golint
+  apidiff:
+    runs-on: ubuntu-latest
+    if: github.base_ref
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@v1
+        with:
+          go-version: 1.13.x
+      - name: Add GOBIN to PATH
+        run: echo "::add-path::$(go env GOPATH)/bin"
+      - name: Install dependencies
+        run: go get golang.org/x/exp/cmd/apidiff
+      - name: Checkout old code
+        uses: actions/checkout@v2
+        with:
+          ref: ${{ github.base_ref }}
+          path: "old"
+      - name: Checkout new code
+        uses: actions/checkout@v2
+        with:
+          path: "new"
+      - name: APIDiff
+        run: ./hack/verify-apidiff.sh -d ../old
+        working-directory: "new"

hack/verify-apidiff.sh

@@ -0,0 +1,125 @@
+#!/usr/bin/env bash
+
+# Copyright 2020 The Kubernetes Authors.
+#
+# 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.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+function usage {
+  local script="$(basename $0)"
+
+  echo >&2 "Usage: ${script} [-r <branch|tag> | -d <dir>]
+
+This script should be run at the root of a module.
+
+-r <branch|tag>
+  Compare the exported API of the local working copy with the 
+  exported API of the local repo at the specified branch or tag.
+
+-d <dir>
+  Compare the exported API of the local working copy with the 
+  exported API of the specified directory, which should point
+  to the root of a different version of the same module.
+
+Examples:
+  ${script} -r master
+  ${script} -r v1.10.0
+  ${script} -r release-1.10
+  ${script} -d /path/to/historical/version
+"
+  exit 1
+}
+
+ref=""
+dir=""
+while getopts r:d: o
+do case "$o" in
+  r)    ref="$OPTARG";;
+  d)    dir="$OPTARG";;
+  [?])  usage;;
+  esac
+done
+
+# If REF and DIR are empty, print usage and error
+if [[ -z "${ref}" && -z "${dir}" ]]; then
+  usage;
+fi
+# If REF and DIR are both set, print usage and error
+if [[ -n "${ref}" && -n "${dir}" ]]; then
+  usage;
+fi
+
+if ! which apidiff > /dev/null; then
+  echo "Installing golang.org/x/exp/cmd/apidiff..."
+  pushd "${TMPDIR:-/tmp}" > /dev/null
+    go get golang.org/x/exp/cmd/apidiff
+  popd > /dev/null
+fi
+
+output=$(mktemp -d -t "apidiff.output.XXXX")
+cleanup_output () { rm -fr "${output}"; }
+trap cleanup_output EXIT
+
+# If ref is set, clone . to temp dir at $ref, and set $dir to the temp dir
+clone=""
+base="${dir}"
+if [[ -n "${ref}" ]]; then
+  base="${ref}"
+  clone=$(mktemp -d -t "apidiff.clone.XXXX")
+  cleanup_clone_and_output () { rm -fr "${clone}"; cleanup_output; }
+  trap cleanup_clone_and_output EXIT
+  git clone . -q --no-tags -b "${ref}" "${clone}"
+  dir="${clone}"
+fi
+
+pushd "${dir}" >/dev/null
+  echo "Inspecting API of ${base}..."
+  go list ./... > packages.txt
+  for pkg in $(cat packages.txt); do
+    mkdir -p "${output}/${pkg}"
+    apidiff -w "${output}/${pkg}/apidiff.output" "${pkg}"
+  done
+popd >/dev/null
+
+retval=0
+
+echo "Comparing with ${base}..."
+for pkg in $(go list ./...); do
+  # New packages are ok
+  if [ ! -f "${output}/${pkg}/apidiff.output" ]; then
+    continue
+  fi
+
+  # Check for incompatible changes to previous packages
+  incompatible=$(apidiff -incompatible "${output}/${pkg}/apidiff.output" "${pkg}")
+  if [[ -n "${incompatible}" ]]; then
+    echo >&2 "FAIL: ${pkg} contains incompatible changes:
+${incompatible}
+"
+    retval=1
+  fi
+done
+
+# Check for removed packages
+removed=$(comm -23 "${dir}/packages.txt" <(go list ./...))
+if [[ -n "${removed}" ]]; then
+  echo >&2 "FAIL: removed packages:
+${removed}
+"
+  retval=1
+fi
+
+exit $retval