support for multi-external env providers

CHANGELOG.md

@@ -2,10 +2,15 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## Unreleased
-### [1.5.1] - 2019-12-10
+### Added
+- support for multiple external environment providers
+
+## [1.5.1] - 2019-12-10
+### Fixed
 - not trimming pipeline history causing memory leak
 
 ## [1.5.0] - 2019-12-09
+### Added
 - support for global environment variables
 - support for external environment variables from an external service
 - abstraction for pipeline execution

environ/provider/external.go

@@ -12,6 +12,19 @@ import (
 	"github.com/drone/runner-go/logger"
 )
 
+// MultiExternal returns a new environment provider that
+// is comprised of multiple external providers, and
+// aggregates their results.
+func MultiExternal(endpoints []string, token string, insecure bool) Provider {
+	var sources []Provider
+	for _, endpoint := range endpoints {
+		sources = append(sources, External(
+			endpoint, token, insecure,
+		))
+	}
+	return Combine(sources...)
+}
+
 // External returns a new external environment variable
 // provider. This provider makes an external API call to
 // list and return environment variables.

environ/provider/external_test.go

@@ -80,6 +80,16 @@ func TestExternal_NotFound(t *testing.T) {
 	}
 }
 
+// This test verifies that multiple external providers
+// are combined into a single provider that concatenates
+// the results.
+func TestMultiExternal(t *testing.T) {
+	provider := MultiExternal([]string{"https://foo", "https://bar"}, "correct-horse-batter-staple", true).(*combined)
+	if len(provider.sources) != 2 {
+		t.Errorf("Expect two provider sources")
+	}
+}
+
 type mockPlugin struct {
 	out map[string]string
 	err error