Fix breaking builds when the cached image was not there with tests (https://github.com/elgohr/Publish-Docker-Github-Action/pull/20)

entrypoint.sh

@@ -45,8 +45,9 @@ if [ ! -z "${INPUT_DOCKERFILE}" ]; then
 fi
 
 if [ ! -z "${INPUT_CACHE}" ]; then
-  docker pull ${DOCKERNAME}
-  BUILDPARAMS="$BUILDPARAMS --cache-from ${DOCKERNAME}"
+  if docker pull ${DOCKERNAME} 2>/dev/null; then
+    BUILDPARAMS="$BUILDPARAMS --cache-from ${DOCKERNAME}"
+  fi
 fi
 
 if [ "${INPUT_SNAPSHOT}" = "true" ]; then

stub.sh

@@ -1,3 +1,7 @@
 #!/bin/sh
-echo "Called mock with: $@"
+parameters="$@"
+echo "Called mock with: ${parameters}"
+if [ "${MOCK_ERROR_CONDITION}" = "${parameters}" ]; then
+  exit 1
+fi
 exit 0

test.bats

@@ -14,6 +14,7 @@ teardown() {
   unset INPUT_CACHE
   unset GITHUB_SHA
   unset INPUT_PULL_REQUESTS
+  unset MOCK_ERROR_CONDITION
 }
 
 @test "it pushes master branch to latest" {
@@ -115,6 +116,25 @@ Called mock with: logout"
   [ "$output" = "$expected" ]
 }
 
+@test "it does not use the cache for building when pulling the former image failed" {
+  export GITHUB_SHA='12169ed809255604e557a82617264e9c373faca7'
+  export MOCK_DATE='197001010101'
+  export INPUT_SNAPSHOT='true'
+  export INPUT_CACHE='true'
+  export MOCK_ERROR_CONDITION='pull my/repository:latest'
+
+  run /entrypoint.sh
+
+  local expected="Called mock with: login -u USERNAME --password-stdin
+Called mock with: pull my/repository:latest
+Called mock with: build -t my/repository:latest -t my/repository:19700101010112169e .
+Called mock with: push my/repository:latest
+Called mock with: push my/repository:19700101010112169e
+Called mock with: logout"
+  echo $output
+  [ "$output" = "$expected" ]
+}
+
 @test "it pushes branch by sha and date with specific Dockerfile" {
   export GITHUB_SHA='12169ed809255604e557a82617264e9c373faca7'
   export MOCK_DATE='197001010101'