Merge pull request #209 from jesseshieh/js/version-error

Friendly error message for unsupported or incorrectly formatted elixir

bin/compile

@@ -33,6 +33,7 @@ export_mix_home
 export_hex_home
 load_config
 check_erlang_version "$erlang_version"
+check_elixir_version "$elixir_version"
 
 check_stack
 clean_cache

elixir_buildpack.config

@@ -1,5 +1,3 @@
-erlang_version=20.1
-elixir_version=1.5.3
 always_rebuild=false
 runtime_path=/app
 release=false

lib/canonical_version.sh

@@ -9,6 +9,11 @@ erlang_builds_url() {
   echo $erlang_builds_url
 }
 
+fetch_elixir_versions() {
+  url="https://repo.hex.pm/builds/elixir/builds.txt"
+  curl -s "$url" | awk '/^v[0-9.]+[- ]/ { print $1 }'
+}
+
 fetch_erlang_versions() {
   if [ "$STACK" = "heroku-20" ]; then
     url="https://repo.hex.pm/builds/otp/ubuntu-20.04/builds.txt"
@@ -32,12 +37,32 @@ exact_erlang_version_available() {
   echo $found
 }
 
+exact_elixir_version_available() {
+  version=$1
+  available_versions=$2
+  found=1
+  while read -r line; do
+    if [ "$line" = "$version" ]; then
+      found=0
+    fi
+  done <<< "$available_versions"
+  echo $found
+}
+
 check_erlang_version() {
   version=$1
   exists=$(exact_erlang_version_available "$version" "$(fetch_erlang_versions)")
   if [ $exists -ne 0 ]; then
-    output_line "Sorry, Erlang $version isn't supported yet. For a list of supported versions, please see https://github.com/HashNuke/heroku-buildpack-elixir#version-support"
+    output_line "Sorry, Erlang '$version' isn't supported yet or isn't formatted correctly. For a list of supported versions, please see https://github.com/HashNuke/heroku-buildpack-elixir#version-support"
     exit 1
   fi
 }
 
+check_elixir_version() {
+  version=$1
+  exists=$(exact_elixir_version_available "$version" "$(fetch_elixir_versions)")
+  if [ $exists -ne 0 ]; then
+    output_line "Sorry, Elixir '$version' isn't supported yet or isn't formatted correctly. For a list of supported versions, please see https://github.com/HashNuke/heroku-buildpack-elixir#version-support"
+    exit 1
+  fi
+}

lib/misc_funcs.sh

@@ -38,7 +38,11 @@ function assert_elixir_version_set() {
   # 0 when found
   # 1 when not found
   # 2 when file does not exist
+
+  set +e
+  # this command is allowed to return a non-zero exit code since that is how we check if the elixir version is set.
   grep -q -e "^elixir_version=" $custom_config_file 2>/dev/null
+  set -e
 
   if [ $? -ne 0 ]; then
     # For now, just print a warning. In the future, we will fail and require an explicit
@@ -61,8 +65,8 @@ function load_config() {
   then
     source $custom_config_file
   else
-    output_line "WARNING: elixir_buildpack.config wasn't found in the app"
-    output_line "Using default config from Elixir buildpack"
+    output_line "Sorry, an elixir_buildpack.config is required. Please see https://github.com/HashNuke/heroku-buildpack-elixir#configuration"
+    exit 1
   fi
 
   assert_elixir_version_set $custom_config_file