From d3dc6830d8425f818468ecffd3881bc4fc951baa Mon Sep 17 00:00:00 2001
From: Elliot Saba <staticfloat@gmail.com>
Date: Mon, 14 Jun 2021 10:06:41 -0700
Subject: [PATCH 1/2] Don't overwrite `BUILDKITE_METAHOOK_HOOKS_PATH`

If we have multiple `metahook` instances, let's not generate multiple
temporary directories; instead just create one (and only dump the
environment variables once).

This fixed an issue with multiple `metahook` instances in a pipeline of
mine.
---
 hooks/environment | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/hooks/environment b/hooks/environment
index 8542e59..34770e6 100644
--- a/hooks/environment
+++ b/hooks/environment
@@ -1,9 +1,11 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-BUILDKITE_METAHOOK_HOOKS_PATH="$(mktemp -d)"
-export BUILDKITE_METAHOOK_HOOKS_PATH
-env | sort | grep "BUILDKITE_PLUGIN_METAHOOK" | uniq >"${BUILDKITE_METAHOOK_HOOKS_PATH}/vars"
+# If users add multiple `metahook` instances, we'll just store our `vars` in the same directory.
+if [[ ! -v "BUILDKITE_METAHOOK_HOOKS_PATH" ]]; then
+  export BUILDKITE_METAHOOK_HOOKS_PATH="$(mktemp -d)"
+  env | sort | grep "BUILDKITE_PLUGIN_METAHOOK" | uniq >"${BUILDKITE_METAHOOK_HOOKS_PATH}/vars"
+fi
 
 if grep -E 'BUILDKITE_PLUGIN_METAHOOK_.+(\.BAT|\.CMD)=' "${BUILDKITE_METAHOOK_HOOKS_PATH}/vars"; then
   echo "Sorry, we had to remove Windows Batch file support in 0.4.0."

From 96495eb7e28be82b3090fc3e2cae5a4b12b7bf40 Mon Sep 17 00:00:00 2001
From: Elliot Saba <staticfloat@gmail.com>
Date: Mon, 14 Jun 2021 17:47:19 +0000
Subject: [PATCH 2/2] Shard `vars` file between multiple plugin configurations

By hashing the `BUILDKITE_PLUGIN_CONFIGURATION` envvar, we can
effectively disambiguate multiple instances of the `metahook` plugin
within a single pipeline.  This allows us to seprate the `vars` file, as
it otherwise can get confused if you have multiple invocations of the
plugin that each use different hooks.
---
 hooks/environment | 9 +++++++--
 hooks/pre-exit    | 6 +++++-
 hooks/run-hook.sh | 4 +++-
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/hooks/environment b/hooks/environment
index 34770e6..3421811 100644
--- a/hooks/environment
+++ b/hooks/environment
@@ -2,12 +2,17 @@
 set -euo pipefail
 
 # If users add multiple `metahook` instances, we'll just store our `vars` in the same directory.
+# We store the `vars` in a file that is namespaced by a hash of the plugin configuration, which
+# allows us to avoid having multiple metahook instances clobber eachother.
 if [[ ! -v "BUILDKITE_METAHOOK_HOOKS_PATH" ]]; then
   export BUILDKITE_METAHOOK_HOOKS_PATH="$(mktemp -d)"
-  env | sort | grep "BUILDKITE_PLUGIN_METAHOOK" | uniq >"${BUILDKITE_METAHOOK_HOOKS_PATH}/vars"
 fi
 
-if grep -E 'BUILDKITE_PLUGIN_METAHOOK_.+(\.BAT|\.CMD)=' "${BUILDKITE_METAHOOK_HOOKS_PATH}/vars"; then
+PLUGIN_CONFIG_HASH=$(cksum <<<"${BUILDKITE_PLUGIN_CONFIGURATION}" | awk '{ print $1 }')
+VARS_FILENAME="vars-${PLUGIN_CONFIG_HASH}"
+env | sort | grep "BUILDKITE_PLUGIN_METAHOOK" | uniq >"${BUILDKITE_METAHOOK_HOOKS_PATH}/${VARS_FILENAME}"
+
+if grep -E 'BUILDKITE_PLUGIN_METAHOOK_.+(\.BAT|\.CMD)=' "${BUILDKITE_METAHOOK_HOOKS_PATH}/${VARS_FILENAME}"; then
   echo "Sorry, we had to remove Windows Batch file support in 0.4.0."
   echo "Please refer to https://github.com/improbable-eng/metahook-buildkite-plugin/tree/master/changelog.md#0.4.0"
   echo ""
diff --git a/hooks/pre-exit b/hooks/pre-exit
index 43d28cf..3646606 100755
--- a/hooks/pre-exit
+++ b/hooks/pre-exit
@@ -1,8 +1,12 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
+PLUGIN_CONFIG_HASH=$(cksum <<<"${BUILDKITE_PLUGIN_CONFIGURATION}" | awk '{ print $1 }')
+VARS_FILENAME="vars-${PLUGIN_CONFIG_HASH}"
 cleanup() {
-  rm -rf "${BUILDKITE_METAHOOK_HOOKS_PATH}"
+  # Delete our `vars` directory, then if the directory itself is empty, delete that too
+  rm -rf "${BUILDKITE_METAHOOK_HOOKS_PATH}/${VARS_FILENAME}"
+  rmdir "${BUILDKITE_METAHOOK_HOOKS_PATH}" 2>/dev/null || true
 }
 trap cleanup EXIT
 
diff --git a/hooks/run-hook.sh b/hooks/run-hook.sh
index 2857e8f..b1bc03f 100755
--- a/hooks/run-hook.sh
+++ b/hooks/run-hook.sh
@@ -5,7 +5,9 @@ hook_name="${1:?1st arg needs to be hook name}"
 upperd="$(echo "${hook_name}" | tr "[:lower:]" "[:upper:]" | sed "s:-:_:")"
 var_name="BUILDKITE_PLUGIN_METAHOOK_${upperd}"
 
-if grep -q "${var_name}" <"${BUILDKITE_METAHOOK_HOOKS_PATH}/vars"; then
+PLUGIN_CONFIG_HASH=$(cksum <<<"${BUILDKITE_PLUGIN_CONFIGURATION}" | awk '{ print $1 }')
+VARS_FILENAME="vars-${PLUGIN_CONFIG_HASH}"
+if grep -q "${var_name}" <"${BUILDKITE_METAHOOK_HOOKS_PATH}/${VARS_FILENAME}"; then
   hook_file="${BUILDKITE_METAHOOK_HOOKS_PATH}/${hook_name}"
 
   echo "#\!/usr/bin/env bash" >"${hook_file}"