Avoid composite action

README.md

@@ -71,4 +71,4 @@ Thanks to [Alexander Pravdin](https://github.com/speller) for the basic idea in
 v2.x unifies `reproducible-containers/buildkit-cache-dance/inject` and `reproducible-containers/buildkit-cache-dance/extract`
 into a single `reproducible-containers/buildkit-cache-dance` action.
 
-However, v2.x seems unstable: [`[v2] "post" steps are executed in a random order`](https://github.com/reproducible-containers/buildkit-cache-dance/issues/1)
+v2.x is still experimental.

action.yml

@@ -11,48 +11,6 @@ inputs:
     default: scratch
     description: "Where the action is stores some temporary files for its processing. Default: `scratch`"
 runs:
-  using: composite
-  steps:
-    - uses: pyTooling/Actions/with-post-step@adef08d3bdef092282614f3b683897cefae82ee3  # v0.4.6
-      with:
-        main: |-
-          set -eux
-          # Clean Directories
-          rm -Rf ${{ inputs.scratch-dir }} && mkdir -p ${{ inputs.scratch-dir }} ${{ inputs.cache-source }}
-          # Prepare Timestamp for Layer Cache Busting
-          date --iso=ns | tee ${{ inputs.cache-source }}/buildstamp
-          # Prepare Dancefile to Access Caches
-          cat > ${{ inputs.scratch-dir }}/Dancefile.inject <<EOF
-          FROM busybox:1
-          COPY buildstamp buildstamp
-          RUN --mount=type=cache,target=${{ inputs.cache-target }} \
-              --mount=type=bind,source=.,target=/var/dance-cache \
-              cp -p -R /var/dance-cache/. ${{ inputs.cache-target }} || true
-          EOF
-          cat ${{ inputs.scratch-dir }}/Dancefile.inject
-          # Inject Data into Docker Cache
-          docker buildx build -f ${{ inputs.scratch-dir }}/Dancefile.inject --tag dance:inject ${{ inputs.cache-source }}
-          # Clean Directories
-          sudo rm -rf ${{ inputs.cache-source }}
-        post: |-
-          set -eux
-          # Prepare Timestamp for Layer Cache Busting
-          date --iso=ns | tee ${{ inputs.scratch-dir }}/buildstamp
-          # Prepare Dancefile to Access Caches
-          cat > ${{ inputs.scratch-dir }}/Dancefile.extract <<EOF
-          FROM busybox:1
-          COPY buildstamp buildstamp
-          RUN --mount=type=cache,target=${{ inputs.cache-target }} \
-              mkdir -p /var/dance-cache/ \
-              && cp -p -R ${{ inputs.cache-target }}/. /var/dance-cache/ || true
-          EOF
-          cat ${{ inputs.scratch-dir }}/Dancefile.extract
-          # Extract Data into Docker Image
-          docker buildx build -f ${{ inputs.scratch-dir }}/Dancefile.extract --tag dance:extract --load ${{ inputs.scratch-dir }}
-          # Create Extraction Image
-          docker rm -f cache-container && docker create -ti --name cache-container dance:extract
-          # Unpack Docker Image into Scratch
-          docker cp -L cache-container:/var/dance-cache - | tar -H posix -x -C ${{ inputs.scratch-dir }}
-          # Move Cache into Its Place
-          sudo rm -rf ${{ inputs.cache-source }}
-          mv ${{ inputs.scratch-dir }}/dance-cache ${{ inputs.cache-source }}
+  using: 'node16'
+  main: 'entrypoint.js'
+  post: 'entrypoint.js'

entrypoint.js

@@ -0,0 +1,49 @@
+// Forked from https://github.com/pyTooling/Actions/blob/v0.4.6/with-post-step/main.js
+// The following copyright header is from the upstream.
+
+/* ================================================================================================================== *
+ * Authors:                                                                                                           *
+ *   Unai Martinez-Corral                                                                                             *
+ *                                                                                                                    *
+ * ================================================================================================================== *
+ * Copyright 2021-2022 Unai Martinez-Corral <[email protected]>                                             *
+ * Copyright 2022 Unai Martinez-Corral <[email protected]>                                                 *
+ *                                                                                                                    *
+ * 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.                                                                                     *
+ *                                                                                                                    *
+ * SPDX-License-Identifier: Apache-2.0                                                                                *
+ * ================================================================================================================== *
+ *                                                                                                                    *
+ * Context:                                                                                                           *
+ * * https://github.com/docker/login-action/issues/72                                                                 *
+ * * https://github.com/actions/runner/issues/1478                                                                    *
+ * ================================================================================================================== */
+const { spawn } = require("child_process");
+const { appendFileSync } = require("fs");
+const { EOL } = require("os");
+
+function run(cmd) {
+  const subprocess = spawn(cmd, { stdio: "inherit", shell: false });
+  subprocess.on("exit", (exitCode) => {
+    process.exitCode = exitCode;
+  });
+}
+
+const key = "POST"
+
+if ( process.env[`STATE_${key}`] !== undefined ) { // Are we in the 'post' step?
+  run("./post");
+} else { // Otherwise, this is the main step
+  appendFileSync(process.env.GITHUB_STATE, `${key}=true${EOL}`);
+  run("./main");
+}

main

@@ -0,0 +1,20 @@
+#!/bin/bash
+set -eux -o pipefail
+: "Argv0: $0"
+: "Clean Directories"
+rm -Rf "$(./read-action-input scratch-dir)" && mkdir -p "$(./read-action-input scratch-dir)" "$(./read-action-input cache-source)"
+: "Prepare Timestamp for Layer Cache Busting"
+date --iso=ns | tee "$(./read-action-input cache-source)"/buildstamp
+: "Prepare Dancefile to Access Caches"
+cat >"$(./read-action-input scratch-dir)"/Dancefile.inject <<EOF
+FROM busybox:1
+COPY buildstamp buildstamp
+RUN --mount=type=cache,target="$(./read-action-input cache-target)" \
+    --mount=type=bind,source=.,target=/var/dance-cache \
+    cp -p -R /var/dance-cache/. "$(./read-action-input cache-target)" || true
+EOF
+cat "$(./read-action-input scratch-dir)"/Dancefile.inject
+: "Inject Data into Docker Cache"
+docker buildx build -f "$(./read-action-input scratch-dir)"/Dancefile.inject --tag dance:inject "$(./read-action-input cache-source)"
+: "Clean Directories"
+sudo rm -rf "$(./read-action-input cache-source)"

post

@@ -0,0 +1,23 @@
+#!/bin/bash
+set -eux -o pipefail
+: "Argv0: $0"
+: "Prepare Timestamp for Layer Cache Busting"
+date --iso=ns | tee "$(./read-action-input scratch-dir)"/buildstamp
+: "Prepare Dancefile to Access Caches"
+cat >"$(./read-action-input scratch-dir)"/Dancefile.extract <<EOF
+FROM busybox:1
+COPY buildstamp buildstamp
+RUN --mount=type=cache,target="$(./read-action-input cache-target)" \
+    mkdir -p /var/dance-cache/ \
+    && cp -p -R "$(./read-action-input cache-target)"/. /var/dance-cache/ || true
+EOF
+cat "$(./read-action-input scratch-dir)"/Dancefile.extract
+: "Extract Data into Docker Image"
+docker buildx build -f "$(./read-action-input scratch-dir)"/Dancefile.extract --tag dance:extract --load "$(./read-action-input scratch-dir)"
+: "Create Extraction Image"
+docker rm -f cache-container && docker create -ti --name cache-container dance:extract
+: "Unpack Docker Image into Scratch"
+docker cp -L cache-container:/var/dance-cache - | tar -H posix -x -C "$(./read-action-input scratch-dir)"
+: "Move Cache into Its Place"
+sudo rm -rf "$(./read-action-input cache-source)"
+mv "$(./read-action-input scratch-dir)"/dance-cache "$(./read-action-input cache-source)"

read-action-input

@@ -0,0 +1,13 @@
+#!/usr/bin/env node
+// helper script for printing kebab-cased env vars.
+// e.g., "foo-bar" -> "INPUT_FOO-BAR".
+//
+// This does not need to be implemented in nodejs,
+// but reimplementing this in sh is hard.
+
+const arg = process.argv[2]; // Equates to "$1" in sh
+const k = "INPUT_" + arg.toUpperCase();
+const v = process.env[k];
+if ( v !== undefined ) {
+  console.log(v);
+}