PLT-7407: Back-end plugin mechanism (#7177)

* begin backend plugin wip

* flesh out rpcplugin. everything done except for minor supervisor stubs

* done with basic plugin infrastructure

* simplify tests

* remove unused test lines

1 files changed, 42 insertions, 0 deletions

diff --git a/plugin/pluginenv/options.go b/plugin/pluginenv/options.go
new file mode 100644
index 000000000..3f83228fb
--- /dev/null
+++ b/plugin/pluginenv/options.go
@@ -0,0 +1,42 @@
+package pluginenv
+
+import (
+	"fmt"
+
+	"github.com/mattermost/platform/plugin"
+	"github.com/mattermost/platform/plugin/rpcplugin"
+)
+
+// APIProvider specifies a function that provides an API implementation to each plugin.
+func APIProvider(provider APIProviderFunc) Option {
+	return func(env *Environment) {
+		env.apiProvider = provider
+	}
+}
+
+// SupervisorProvider specifies a function that provides a Supervisor implementation to each plugin.
+// If unspecified, DefaultSupervisorProvider is used.
+func SupervisorProvider(provider SupervisorProviderFunc) Option {
+	return func(env *Environment) {
+		env.supervisorProvider = provider
+	}
+}
+
+// SearchPath specifies a directory that contains the plugins to launch.
+func SearchPath(path string) Option {
+	return func(env *Environment) {
+		env.searchPath = path
+	}
+}
+
+// DefaultSupervisorProvider chooses a supervisor based on the plugin's manifest contents. E.g. if
+// the manifest specifies a backend executable, it will be given an rpcplugin.Supervisor.
+func DefaultSupervisorProvider(bundle *plugin.BundleInfo) (plugin.Supervisor, error) {
+	if bundle.Manifest == nil {
+		return nil, fmt.Errorf("a manifest is required")
+	}
+	if bundle.Manifest.Backend == nil {
+		return nil, fmt.Errorf("invalid manifest: at this time, only backend plugins are supported")
+	}
+	return rpcplugin.SupervisorProvider(bundle)
+}