From dfeb0bcf5c9c9e7f56ee0923a68f8449b0ae635e Mon Sep 17 00:00:00 2001
From: Ed Morley <501702+edmorley@users.noreply.github.com>
Date: Fri, 6 Nov 2020 14:08:57 +0000
Subject: [PATCH] Fail the build early on unsupported stacks

In order to prevent the build completing apparently successfully, but
the app fail to boot at runtime due to stack incompatibility.

At first glance this would seem unnecessary due to the stack-specific
URL meaning the `curl` would 404 on supported stacks. However #165
means the Cedar-14 binary is installed on all stacks, and on Heroku-20
causes the failures at runtime seen in #166.

Future PRs will fix the curl/binary handling to use stack-specific URLs,
however it's still nicer to explicitly handle unsupported stacks with a
clear error message than a 404.
---
 CHANGELOG.md |  1 +
 bin/compile  | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 48effa5f..2a56ff97 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* [#177](https://github.com/heroku/heroku-buildpack-static/pull/177) Fail the build early on unsupported stacks
 
 ## v4 (2019-09-18)
 
diff --git a/bin/compile b/bin/compile
index 6bdad80a..4effc6f7 100755
--- a/bin/compile
+++ b/bin/compile
@@ -8,6 +8,16 @@ cache_dir=$2
 env_dir=$3
 bp_dir=$(dirname $(dirname $0))
 
+case "${STACK}" in
+  cedar-14|heroku-16|heroku-18)
+    # Supported stack
+    ;;
+  *)
+    echo "Stack ${STACK} is not supported!"
+    exit 1
+    ;;
+esac
+
 fetch_nginx_tarball() {
     local version="1.9.7"
     local tarball_file="nginx-$version.tgz"