From 25c0b98363a8bbad9b14b1374af36bcf36477d6d Mon Sep 17 00:00:00 2001
From: Joel Vasallo <joelvasallo@gmail.com>
Date: Thu, 18 Oct 2018 15:10:04 -0500
Subject: [PATCH] feat: ability to specify runtime OSs where shell-local should
 run

---
 common/shell-local/config.go                  |  3 +
 common/shell-local/run.go                     | 64 ++++++++++++-------
 .../docs/provisioners/shell-local.html.md     |  8 +++
 3 files changed, 53 insertions(+), 22 deletions(-)

diff --git a/common/shell-local/config.go b/common/shell-local/config.go
index 56f9e05cd..bd895b547 100644
--- a/common/shell-local/config.go
+++ b/common/shell-local/config.go
@@ -29,6 +29,9 @@ type Config struct {
 	// The shebang value used when running inline scripts.
 	InlineShebang string `mapstructure:"inline_shebang"`
 
+	// An array of multiple Runtime OSs to run on.
+	OnlyOn []string
+
 	// The file extension to use for the file generated from the inline commands
 	TempfileExtension string `mapstructure:"tempfile_extension"`
 
diff --git a/common/shell-local/run.go b/common/shell-local/run.go
index c8f6160fc..505823833 100644
--- a/common/shell-local/run.go
+++ b/common/shell-local/run.go
@@ -6,6 +6,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"runtime"
 	"sort"
 	"strings"
 
@@ -58,31 +59,50 @@ func Run(ui packer.Ui, config *Config) (bool, error) {
 		if err != nil {
 			return false, err
 		}
-		ui.Say(fmt.Sprintf("Running local shell script: %s", script))
 
-		comm := &Communicator{
-			ExecuteCommand: interpolatedCmds,
+		// Check if command can execute against runtime.
+		runCommand := false
+		if len(config.OnlyOn) > 0 {
+			for _, os := range config.OnlyOn {
+				if os == runtime.GOOS {
+					runCommand = true
+				}
+			}
+		} else {
+			runCommand = true
 		}
 
-		// The remoteCmd generated here isn't actually run, but it allows us to
-		// use the same interafce for the shell-local communicator as we use for
-		// the other communicators; ultimately, this command is just used for
-		// buffers and for reading the final exit status.
-		flattenedCmd := strings.Join(interpolatedCmds, " ")
-		cmd := &packer.RemoteCmd{Command: flattenedCmd}
-		log.Printf("[INFO] (shell-local): starting local command: %s", flattenedCmd)
-		if err := cmd.StartWithUi(comm, ui); err != nil {
-			return false, fmt.Errorf(
-				"Error executing script: %s\n\n"+
-					"Please see output above for more information.",
-				script)
-		}
-		if cmd.ExitStatus != 0 {
-			return false, fmt.Errorf(
-				"Erroneous exit code %d while executing script: %s\n\n"+
-					"Please see output above for more information.",
-				cmd.ExitStatus,
-				script)
+		if runCommand {
+			ui.Say(fmt.Sprintf("Running local shell script: %s", script))
+
+			comm := &Communicator{
+				ExecuteCommand: interpolatedCmds,
+			}
+
+			// The remoteCmd generated here isn't actually run, but it allows us to
+			// use the same interafce for the shell-local communicator as we use for
+			// the other communicators; ultimately, this command is just used for
+			// buffers and for reading the final exit status.
+			flattenedCmd := strings.Join(interpolatedCmds, " ")
+
+			cmd := &packer.RemoteCmd{Command: flattenedCmd}
+			log.Printf("[INFO] (shell-local): starting local command: %s", flattenedCmd)
+			if err := cmd.StartWithUi(comm, ui); err != nil {
+				return false, fmt.Errorf(
+					"Error executing script: %s\n\n"+
+						"Please see output above for more information.",
+					script)
+			}
+			if cmd.ExitStatus != 0 {
+				return false, fmt.Errorf(
+					"Erroneous exit code %d while executing script: %s\n\n"+
+						"Please see output above for more information.",
+					cmd.ExitStatus,
+					script)
+			}
+		} else {
+			ui.Say(fmt.Sprintf("Skipping local shell script due to runtime OS: %s", script))
+			log.Printf("[INFO] (shell-local): skipping command due to runtime OS not specified.")
 		}
 	}
 
diff --git a/website/source/docs/provisioners/shell-local.html.md b/website/source/docs/provisioners/shell-local.html.md
index 5932ed69d..99724cb86 100644
--- a/website/source/docs/provisioners/shell-local.html.md
+++ b/website/source/docs/provisioners/shell-local.html.md
@@ -108,6 +108,14 @@ Optional parameters:
     **Important:** If you customize this, be sure to include something like the
     `-e` flag, otherwise individual steps failing won't fail the provisioner.
 
+-  `onlyon` (array of strings) - This is an array of 
+    [runtime operating systems](https://golang.org/doc/install/source#environment)
+    where `shell-local` will only run on. This allows you to run `shell-local` *only* 
+    on specific compatible operating systems. If specified, shell-local will only
+    execute if runtime operating system is in the list; otherwise it will skip the 
+    `shell-local` command. The default behavior is for `shell-local` to run if 
+    `onlyon` is not specified.
+
 -  `use_linux_pathing` (bool) - This is only relevant to windows hosts. If you
    are running Packer in a Windows environment with the Windows Subsystem for
    Linux feature enabled, and would like to invoke a bash script rather than