Feature(Plugins): Enable platform specific commands (#5176)

* Add logic for platform specific commands to plugins
* Add plugins doc updated to incorporate platform specific commands
* Add condition for os match:  If OS matches and there is no more specific match, the command
will be executed

cmd/helm/load_plugins.go

@@ -78,7 +78,11 @@ func loadPlugins(baseCmd *cobra.Command, out io.Writer) {
 				// PrepareCommand uses os.ExpandEnv and expects the
 				// setupEnv vars.
 				plugin.SetupPluginEnv(settings, md.Name, plug.Dir)
-				main, argv := plug.PrepareCommand(u)
+				main, argv, prepCmdErr := plug.PrepareCommand(u)
+				if prepCmdErr != nil {
+					os.Stderr.WriteString(prepCmdErr.Error())
+					return errors.Errorf("plugin %q exited with error", md.Name)
+				}
 
 				prog := exec.Command(main, argv...)
 				prog.Env = os.Environ()

docs/plugins.md

@@ -64,13 +64,22 @@ The core of a plugin is a simple YAML file named `plugin.yaml`.
 Here is a plugin YAML for a plugin that adds support for Keybase operations:
 
 ```
-name: "keybase"
+name: "last"
 version: "0.1.0"
-usage: "Integrate Keybase.io tools with Helm"
-description: |-
-  This plugin provides Keybase services to Helm.
+usage: "get the last release name"
+description: "get the last release name""
 ignoreFlags: false
-command: "$HELM_PLUGIN_DIR/keybase.sh"
+command: "$HELM_BIN --host $TILLER_HOST list --short --max 1 --date -r"
+platformCommand:
+  - os: linux
+    arch: i386
+    command: "$HELM_BIN list --short --max 1 --date -r"
+  - os: linux
+    arch: amd64
+    command: "$HELM_BIN list --short --max 1 --date -r"
+  - os: windows
+    arch: amd64
+    command: "$HELM_BIN list --short --max 1 --date -r"
 ```
 
 The `name` is the name of the plugin. When Helm executes it plugin, this is the
@@ -91,17 +100,31 @@ The `ignoreFlags` switch tells Helm to _not_ pass flags to the plugin. So if a
 plugin is called with `helm myplugin --foo` and `ignoreFlags: true`, then `--foo`
 is silently discarded.
 
-Finally, and most importantly, `command` is the command that this plugin will
-execute when it is called. Environment variables are interpolated before the plugin
-is executed. The pattern above illustrates the preferred way to indicate where
-the plugin program lives.
+Finally, and most importantly, `platformCommand` or `command` is the command
+that this plugin will execute when it is called. The `platformCommand` section
+defines the OS/Architecture specific variations of a command. The following
+rules will apply in deciding which command to use:
+
+- If `platformCommand` is present, it will be searched first.
+- If both `os` and `arch` match the current platform, search will stop and the
+command will be used.
+- If `os` matches and there is no more specific `arch` match, the command
+will be used.
+- If no `platformCommand` match is found, the default `command` will be used.
+- If no matches are found in `platformCommand` and no `command` is present,
+Helm will exit with an error.
+
+Environment variables are interpolated before the plugin is executed. The
+pattern above illustrates the preferred way to indicate where the plugin
+program lives.
 
 There are some strategies for working with plugin commands:
 
-- If a plugin includes an executable, the executable for a `command:` should be
-  packaged in the plugin directory.
-- The `command:` line will have any environment variables expanded before
-  execution. `$HELM_PLUGIN_DIR` will point to the plugin directory.
+- If a plugin includes an executable, the executable for a
+`platformCommand:` or a `command:` should be packaged in the plugin directory.
+- The `platformCommand:` or `command:` line will have any environment
+variables expanded before execution. `$HELM_PLUGIN_DIR` will point to the
+plugin directory.
 - The command itself is not executed in a shell. So you can't oneline a shell script.
 - Helm injects lots of configuration into environment variables. Take a look at
   the environment to see what information is available.

pkg/plugin/plugin.go

@@ -16,9 +16,11 @@ limitations under the License.
 package plugin // import "k8s.io/helm/pkg/plugin"
 
 import (
+	"fmt"
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 
 	helm_env "k8s.io/helm/pkg/helm/environment"
@@ -38,6 +40,13 @@ type Downloaders struct {
 	Command string `json:"command"`
 }
 
+// PlatformCommand represents a command for a particular operating system and architecture
+type PlatformCommand struct {
+	OperatingSystem string `json:"os"`
+	Architecture    string `json:"arch"`
+	Command         string `json:"command"`
+}
+
 // Metadata describes a plugin.
 //
 // This is the plugin equivalent of a chart.Metadata.
@@ -62,7 +71,15 @@ type Metadata struct {
 	//
 	// Note that command is not executed in a shell. To do so, we suggest
 	// pointing the command to a shell script.
-	Command string `json:"command"`
+	//
+	// The following rules will apply to processing commands:
+	// - If platformCommand is present, it will be searched first
+	// - If both OS and Arch match the current platform, search will stop and the command will be executed
+	// - If OS matches and there is no more specific match, the command will be executed
+	// - If no OS/Arch match is found, the default command will be executed
+	// - If no command is present and no matches are found in platformCommand, Helm will exit with an error
+	PlatformCommand []PlatformCommand `json:"platformCommand"`
+	Command         string            `json:"command"`
 
 	// IgnoreFlags ignores any flags passed in from Helm
 	//
@@ -87,14 +104,47 @@ type Plugin struct {
 	Dir string
 }
 
-// PrepareCommand takes a Plugin.Command and prepares it for execution.
+// The following rules will apply to processing the Plugin.PlatformCommand.Command:
+// - If both OS and Arch match the current platform, search will stop and the command will be prepared for execution
+// - If OS matches and there is no more specific match, the command will be prepared for execution
+// - If no OS/Arch match is found, return nil
+func getPlatformCommand(platformCommands []PlatformCommand) []string {
+	var command []string
+	for _, platformCommand := range platformCommands {
+		if strings.EqualFold(platformCommand.OperatingSystem, runtime.GOOS) {
+			command = strings.Split(os.ExpandEnv(platformCommand.Command), " ")
+		}
+		if strings.EqualFold(platformCommand.OperatingSystem, runtime.GOOS) && strings.EqualFold(platformCommand.Architecture, runtime.GOARCH) {
+			return strings.Split(os.ExpandEnv(platformCommand.Command), " ")
+		}
+	}
+	return command
+}
+
+// PrepareCommand takes a Plugin.PlatformCommand.Command, a Plugin.Command and will applying the following processing:
+// - If platformCommand is present, it will be searched first
+// - If both OS and Arch match the current platform, search will stop and the command will be prepared for execution
+// - If OS matches and there is no more specific match, the command will be prepared for execution
+// - If no OS/Arch match is found, the default command will be prepared for execution
+// - If no command is present and no matches are found in platformCommand, will exit with an error
 //
 // It merges extraArgs into any arguments supplied in the plugin. It
 // returns the name of the command and an args array.
 //
 // The result is suitable to pass to exec.Command.
-func (p *Plugin) PrepareCommand(extraArgs []string) (string, []string) {
-	parts := strings.Split(os.ExpandEnv(p.Metadata.Command), " ")
+func (p *Plugin) PrepareCommand(extraArgs []string) (string, []string, error) {
+	var parts []string
+	platCmdLen := len(p.Metadata.PlatformCommand)
+	if platCmdLen > 0 {
+		parts = getPlatformCommand(p.Metadata.PlatformCommand)
+	}
+	if platCmdLen == 0 || parts == nil {
+		parts = strings.Split(os.ExpandEnv(p.Metadata.Command), " ")
+	}
+	if parts == nil || len(parts) == 0 || parts[0] == "" {
+		return "", nil, fmt.Errorf("No plugin command is applicable")
+	}
+
 	main := parts[0]
 	baseArgs := []string{}
 	if len(parts) > 1 {
@@ -103,7 +153,7 @@ func (p *Plugin) PrepareCommand(extraArgs []string) (string, []string) {
 	if !p.Metadata.IgnoreFlags {
 		baseArgs = append(baseArgs, extraArgs...)
 	}
-	return main, baseArgs
+	return main, baseArgs, nil
 }
 
 // LoadDir loads a plugin from the given directory.

pkg/plugin/plugin_test.go

@@ -17,20 +17,15 @@ package plugin // import "k8s.io/helm/pkg/plugin"
 
 import (
 	"reflect"
+	"runtime"
 	"testing"
 )
 
-func TestPrepareCommand(t *testing.T) {
-	p := &Plugin{
-		Dir: "/tmp", // Unused
-		Metadata: &Metadata{
-			Name:    "test",
-			Command: "echo -n foo",
-		},
+func checkCommand(p *Plugin, extraArgs []string, osStrCmp string, t *testing.T) {
+	cmd, args, err := p.PrepareCommand(extraArgs)
+	if err != nil {
+		t.Errorf(err.Error())
 	}
-	argv := []string{"--debug", "--foo", "bar"}
-
-	cmd, args := p.PrepareCommand(argv)
 	if cmd != "echo" {
 		t.Errorf("Expected echo, got %q", cmd)
 	}
@@ -39,7 +34,7 @@ func TestPrepareCommand(t *testing.T) {
 		t.Errorf("expected 5 args, got %d", l)
 	}
 
-	expect := []string{"-n", "foo", "--debug", "--foo", "bar"}
+	expect := []string{"-n", osStrCmp, "--debug", "--foo", "bar"}
 	for i := 0; i < len(args); i++ {
 		if expect[i] != args[i] {
 			t.Errorf("Expected arg=%q, got %q", expect[i], args[i])
@@ -48,14 +43,17 @@ func TestPrepareCommand(t *testing.T) {
 
 	// Test with IgnoreFlags. This should omit --debug, --foo, bar
 	p.Metadata.IgnoreFlags = true
-	cmd, args = p.PrepareCommand(argv)
+	cmd, args, err = p.PrepareCommand(extraArgs)
+	if err != nil {
+		t.Errorf(err.Error())
+	}
 	if cmd != "echo" {
 		t.Errorf("Expected echo, got %q", cmd)
 	}
 	if l := len(args); l != 2 {
 		t.Errorf("expected 2 args, got %d", l)
 	}
-	expect = []string{"-n", "foo"}
+	expect = []string{"-n", osStrCmp}
 	for i := 0; i < len(args); i++ {
 		if expect[i] != args[i] {
 			t.Errorf("Expected arg=%q, got %q", expect[i], args[i])
@@ -63,6 +61,109 @@ func TestPrepareCommand(t *testing.T) {
 	}
 }
 
+func TestPrepareCommand(t *testing.T) {
+	p := &Plugin{
+		Dir: "/tmp", // Unused
+		Metadata: &Metadata{
+			Name:    "test",
+			Command: "echo -n foo",
+		},
+	}
+	argv := []string{"--debug", "--foo", "bar"}
+
+	checkCommand(p, argv, "foo", t)
+}
+
+func TestPlatformPrepareCommand(t *testing.T) {
+	p := &Plugin{
+		Dir: "/tmp", // Unused
+		Metadata: &Metadata{
+			Name:    "test",
+			Command: "echo -n os-arch",
+			PlatformCommand: []PlatformCommand{
+				{OperatingSystem: "linux", Architecture: "i386", Command: "echo -n linux-i386"},
+				{OperatingSystem: "linux", Architecture: "amd64", Command: "echo -n linux-amd64"},
+				{OperatingSystem: "windows", Architecture: "amd64", Command: "echo -n win-64"},
+			},
+		},
+	}
+	argv := []string{"--debug", "--foo", "bar"}
+	var osStrCmp string
+	os := runtime.GOOS
+	arch := runtime.GOARCH
+	if os == "linux" && arch == "i386" {
+		osStrCmp = "linux-i386"
+	} else if os == "linux" && arch == "amd64" {
+		osStrCmp = "linux-amd64"
+	} else if os == "windows" && arch == "amd64" {
+		osStrCmp = "win-64"
+	} else {
+		osStrCmp = "os-arch"
+	}
+
+	checkCommand(p, argv, osStrCmp, t)
+}
+
+func TestPartialPlatformPrepareCommand(t *testing.T) {
+	p := &Plugin{
+		Dir: "/tmp", // Unused
+		Metadata: &Metadata{
+			Name:    "test",
+			Command: "echo -n os-arch",
+			PlatformCommand: []PlatformCommand{
+				{OperatingSystem: "linux", Architecture: "i386", Command: "echo -n linux-i386"},
+				{OperatingSystem: "windows", Architecture: "amd64", Command: "echo -n win-64"},
+			},
+		},
+	}
+	argv := []string{"--debug", "--foo", "bar"}
+	var osStrCmp string
+	os := runtime.GOOS
+	arch := runtime.GOARCH
+	if os == "linux" {
+		osStrCmp = "linux-i386"
+	} else if os == "windows" && arch == "amd64" {
+		osStrCmp = "win-64"
+	} else {
+		osStrCmp = "os-arch"
+	}
+
+	checkCommand(p, argv, osStrCmp, t)
+}
+
+func TestNoPrepareCommand(t *testing.T) {
+	p := &Plugin{
+		Dir: "/tmp", // Unused
+		Metadata: &Metadata{
+			Name: "test",
+		},
+	}
+	argv := []string{"--debug", "--foo", "bar"}
+
+	_, _, err := p.PrepareCommand(argv)
+	if err == nil {
+		t.Errorf("Expected error to be returned")
+	}
+}
+
+func TestNoMatchPrepareCommand(t *testing.T) {
+	p := &Plugin{
+		Dir: "/tmp", // Unused
+		Metadata: &Metadata{
+			Name: "test",
+			PlatformCommand: []PlatformCommand{
+				{OperatingSystem: "no-os", Architecture: "amd64", Command: "echo -n linux-i386"},
+			},
+		},
+	}
+	argv := []string{"--debug", "--foo", "bar"}
+
+	_, _, err := p.PrepareCommand(argv)
+	if err == nil {
+		t.Errorf("Expected error to be returned")
+	}
+}
+
 func TestLoadDir(t *testing.T) {
 	dirname := "testdata/plugdir/hello"
 	plug, err := LoadDir(dirname)