Fix support for Heroku-24 (#15)

* try with Dockerfile

* add heroku 24

* separate packages for heroku-24

* remove packages from heroku-24

these no longer exist

* Test that Chrome is on PATH and can launch

To make testing fully representative of the Heroku platform, we have to run
the built app against the run image and not the build image. (Whilst Heroku CI
will use the build image, some apps will use the buildpack outside of CI, and so
against the run image which has fewer system libraries than the build image.)

* Add a `.dockerignore` to speed up local iteration

This prevents unnecessary Docker cache invalidation when editing files
that don't affect the image, meaning quicker iteration times when
developing on this buildpack locally.

* Fix packages on Heroku-24

Fixes this error:

```
chrome: error while loading shared libraries: libasound.so.2: cannot open shared object file: No such file or directory
```

And also cleans up the packages list, removing some packages that
either are no longer needed, or already exist in the base image. This
is safe to do now that `bin/test.sh` checks for missing shared libraries.

---------

Co-authored-by: Ed Morley <501702+edmorley@users.noreply.github.com>

.dockerignore

@@ -0,0 +1,3 @@
+.github/
+bin/test.sh
+Dockerfile

.github/workflows/build-and-test.yml

@@ -6,23 +6,10 @@ jobs:
   test:
     strategy:
       matrix:
-        stack: [heroku-20, heroku-22, heroku-24]
+        stack_version: [20, 22, 24]
     runs-on: ubuntu-latest
 
     steps:
     - uses: actions/checkout@v3
-
-    - name: Run Buildpack Compile
-      run: |
-        ./bin/compile . . .
-      env:
-        STACK: ${{ matrix.stack }}
-
     - name: Check Installation
-      run: |
-        # Trick the profile script into using working dir as HOME
-        HOME="$(pwd)"
-        # Verify profile script puts Chrome & Chromedriver on the PATH
-        source .profile.d/chrome-for-testing.sh
-        chrome --version
-        chromedriver --version
+      run: ./bin/test.sh ${{ matrix.stack_version }}

Dockerfile

@@ -0,0 +1,35 @@
+ARG STACK_VERSION
+FROM --platform=linux/amd64 heroku/heroku:${STACK_VERSION}-build as build
+
+# This ARG duplication is required since the lines before and after the 'FROM' are in different scopes.
+ARG STACK_VERSION
+ENV STACK="heroku-${STACK_VERSION}"
+
+# On Heroku-24 and later the default user is not root.
+# Once support for Heroku-22 and older is removed, the `useradd` steps below can be removed.
+USER root
+
+# Emulate the platform where root access is not available
+RUN useradd -m non-root-user
+USER non-root-user
+RUN mkdir -p /tmp/build /tmp/cache /tmp/env
+COPY --chown=non-root-user . /buildpack
+
+# Sanitize the environment seen by the buildpack, to prevent reliance on
+# environment variables that won't be present when it's run by Heroku CI.
+RUN env -i PATH=$PATH HOME=$HOME STACK=$STACK /buildpack/bin/detect /tmp/build
+RUN env -i PATH=$PATH HOME=$HOME STACK=$STACK /buildpack/bin/compile /tmp/build /tmp/cache /tmp/env
+
+# We must then test against the run image since that has fewer system libraries installed.
+FROM --platform=linux/amd64 heroku/heroku:${STACK_VERSION}
+USER root
+# Emulate the platform where root access is not available
+RUN useradd -m non-root-user
+USER non-root-user
+COPY --from=build --chown=non-root-user /tmp/build /app
+# Emulate the platform which sources all .profile.d/ scripts on app boot.
+RUN echo 'for f in /app/.profile.d/*; do source "${f}"; done' > /app/.profile
+ENV HOME=/app
+WORKDIR /app
+# We have to use a login bash shell otherwise the .profile script won't be run.
+CMD ["bash", "-l"]

bin/install-chrome-dependencies

@@ -14,10 +14,10 @@
 topic "Installing Chrome dependencies"
 
 # Install correct dependencies according to $STACK
+# The package list is validated by bin/test.sh - see its output to identify any missing libraries.
+# Also look here for more packages/notes https://developers.google.com/web/tools/puppeteer/troubleshooting
 case "${STACK}" in
-  "heroku-20" | "heroku-22" | "heroku-24")
-    # the package list is found by using ci:debug then running ldd $GOOGLE_CHROME_BIN | grep not
-    # also look here for more packages/notes https://developers.google.com/web/tools/puppeteer/troubleshooting
+  "heroku-20" | "heroku-22")
     PACKAGES="
       gconf-service
       libappindicator1
@@ -46,6 +46,21 @@ case "${STACK}" in
       fonts-liberation
     "
     ;;
+  "heroku-24")
+    PACKAGES="
+      fonts-liberation
+      libasound2t64
+      libatk-bridge2.0-0
+      libatk1.0-0
+      libcups2
+      libgbm1
+      libxcomposite1
+      libxdamage1
+      libxfixes3
+      libxkbcommon0
+      libxrandr2
+    "
+    ;;
   *)
     error "STACK must be 'heroku-20', 'heroku-22' or 'heroku-24', not '${STACK}'."
 esac

bin/test.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+STACK_VERSION="${1:?'Error: The stack version number must be specified as the first argument.'}"
+
+set -x
+
+docker build --progress=plain --build-arg="STACK_VERSION=${STACK_VERSION}" -t heroku-buildpack-chrome-for-testing .
+
+# Note: All of the container commands must be run via a login bash shell otherwise the profile.d scripts won't be run.
+
+# Check the profile.d scripts correctly added the binaries to PATH.
+docker run heroku-buildpack-chrome-for-testing bash -l -c 'chrome --version'
+docker run heroku-buildpack-chrome-for-testing bash -l -c 'chromedriver --version'
+
+# Check that there are no missing dynamically linked libraries.
+docker run heroku-buildpack-chrome-for-testing bash -l -c 'ldd $(which chrome)'
+docker run heroku-buildpack-chrome-for-testing bash -l -c 'ldd $(which chromedriver)'
+
+# Check Chrome can fully boot in both new and old headless modes.
+docker run heroku-buildpack-chrome-for-testing bash -l -c 'chrome --no-sandbox --headless=new --screenshot https://google.com'
+docker run heroku-buildpack-chrome-for-testing bash -l -c 'chrome --no-sandbox --headless=old --screenshot https://google.com'