Extensible Fission CLI (#743)

This PR introduces extensibility to the Fission CLI. The principle behind the design of this extensibility is taken from the approach git uses: the main binary (fission) calls other binaries (fission-workflows) - which it discovers using simple prefix-rules - based on specific commands (fission workflow <command>).

fission/plugin/plugin_test.go

@@ -0,0 +1,104 @@
+/*
+Copyright 2016 The Fission Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package plugin
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFind(t *testing.T) {
+	os.Clearenv()
+	testDir := path.Join(os.TempDir(), fmt.Sprintf("fission-test-plugins-%v", time.Now().UnixNano()))
+	err := os.MkdirAll(testDir, os.ModePerm)
+	if err != nil {
+		t.FailNow()
+	}
+	defer os.RemoveAll(testDir)
+	testBinary := path.Join(testDir, "foo")
+	md := &Metadata{
+		Name:    "foo",
+		Version: "1.0.1",
+		Usage:   "Usage help",
+		Aliases: []string{"bar"},
+	}
+	jsonMd, err := json.Marshal(md)
+	if err != nil {
+		t.FailNow()
+	}
+	err = ioutil.WriteFile(testBinary, []byte(fmt.Sprintf("#!/bin/sh\necho '%v'", string(jsonMd))), os.ModePerm)
+	if err != nil {
+		t.FailNow()
+	}
+
+	err = os.Setenv("PATH", testDir)
+	if err != nil {
+		t.FailNow()
+	}
+	Prefix = ""
+
+	found, err := Find(md.Name)
+	os.RemoveAll(testDir)
+	assert.NoError(t, err)
+	assert.NotEmpty(t, found)
+	assert.Equal(t, md.Name, found.Name)
+	assert.Equal(t, path.Join(testDir, md.Name), found.Path)
+	assert.Equal(t, md.Aliases, found.Aliases)
+	assert.Equal(t, md.Usage, found.Usage)
+	assert.Equal(t, md.Version, found.Version)
+}
+
+func TestExec(t *testing.T) {
+	os.Clearenv()
+	testDir := path.Join(os.TempDir(), fmt.Sprintf("fission-test-plugins-%v", time.Now().UnixNano()))
+	err := os.MkdirAll(testDir, os.ModePerm)
+	if err != nil {
+		t.FailNow()
+	}
+	defer os.RemoveAll(testDir)
+	testBinary := path.Join(testDir, "foo")
+	md := &Metadata{
+		Name:    "foo",
+		Version: "1.0.1",
+		Usage:   "Usage help",
+		Aliases: []string{"bar"},
+		Path:    path.Join(testBinary),
+	}
+	jsonMd, err := json.Marshal(md)
+	if err != nil {
+		t.FailNow()
+	}
+	err = ioutil.WriteFile(testBinary, []byte(fmt.Sprintf("#!/bin/sh\necho '%v'", string(jsonMd))), os.ModePerm)
+	if err != nil {
+		t.FailNow()
+	}
+	err = os.Setenv("PATH", testDir)
+	if err != nil {
+		t.FailNow()
+	}
+	Prefix = ""
+	err = Exec(md, nil)
+	os.RemoveAll(testDir)
+	assert.NoError(t, err)
+}