daemon: support programs with arguments

Add support for specifying arguments in both launchd and systemd
applications. In launchd, these args are specified in a "ProgramArguments"
array; in systemd, they are simply appended to the program name (as someone
would run a program on the command line).

Note that "ProgramArguments" in the 'launchd' plist now always has at least
one element: the path to the executable program. This aligns 'launchd' to
standard argument conventions [1]; although it does not yet affect
'git-bundle-web-server' (the only usage of the 'launchd' code at this
point), it will in future patches when arguments & arg parsing are added.

Finally, add & update unit tests covering the use of arguments in both
launchd & systemd.

[1] https://man7.org/linux/man-pages/man3/execvp.3.html

Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

internal/daemon/daemon.go

@@ -11,6 +11,7 @@ type DaemonConfig struct {
 	Label       string
 	Description string
 	Program     string
+	Arguments   []string
 }
 
 type DaemonProvider interface {

internal/daemon/launchd.go

@@ -7,6 +7,7 @@ import (
 	"path/filepath"
 
 	"github.com/github/git-bundle-server/internal/common"
+	"github.com/github/git-bundle-server/internal/utils"
 )
 
 type xmlItem struct {
@@ -36,6 +37,15 @@ func (p *plist) addKeyValue(key string, value any) {
 	switch value := value.(type) {
 	case string:
 		p.Config.Elements = append(p.Config.Elements, xmlItem{XMLName: xmlName("string"), Value: value})
+	case []string:
+		p.Config.Elements = append(p.Config.Elements,
+			xmlArray{
+				XMLName: xmlName("array"),
+				Elements: utils.Map(value, func(e string) interface{} {
+					return xmlItem{XMLName: xmlName("string"), Value: e}
+				}),
+			},
+		)
 	default:
 		panic("Invalid value type in 'addKeyValue'")
 	}
@@ -61,6 +71,18 @@ func (c *launchdConfig) toPlist() *plist {
 	p.addKeyValue("StandardOutPath", c.StdOut)
 	p.addKeyValue("StandardErrorPath", c.StdErr)
 
+	// IMPORTANT!!!
+	// You must explicitly set the first argument to the executable path
+	// because 'ProgramArguments' maps directly 'argv' in 'execvp'. The
+	// programs calling this library likely will, by convention, assume the
+	// first element of 'argv' is the executing program.
+	// See https://www.unix.com/man-page/osx/5/launchd.plist/ and
+	// https://man7.org/linux/man-pages/man3/execvp.3.html for more details.
+	args := make([]string, len(c.Arguments)+1)
+	args[0] = c.Program
+	copy(args[1:], c.Arguments[:])
+	p.addKeyValue("ProgramArguments", args)
+
 	return p
 }
 

internal/daemon/launchd_test.go

@@ -129,6 +129,11 @@ var launchdCreatePlistTests = []struct {
 			"<key>StandardErrorPath</key>",
 			"<string>/dev/null</string>",
 
+			"<key>ProgramArguments</key>",
+			"<array>",
+			fmt.Sprintf("<string>%s</string>", basicDaemonConfig.Program),
+			"</array>",
+
 			"</dict>",
 			"</plist>",
 		},
@@ -161,6 +166,47 @@ var launchdCreatePlistTests = []struct {
 			"<key>StandardErrorPath</key>",
 			"<string>/dev/null</string>",
 
+			"<key>ProgramArguments</key>",
+			"<array>",
+			"<string>/path/to/the/program with a space</string>",
+			"</array>",
+
+			"</dict>",
+			"</plist>",
+		},
+	},
+	{
+		title: "Created plist captures args",
+		config: &daemon.DaemonConfig{
+			Label:     "test-with-args",
+			Program:   "/path/to/the/program",
+			Arguments: []string{"--test", "another-arg"},
+		},
+		expectedPlistLines: []string{
+			`<?xml version="1.0" encoding="UTF-8"?>`,
+			`<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">`,
+			`<plist version="1.0">`,
+			"<dict>",
+
+			"<key>Label</key>",
+			"<string>test-with-args</string>",
+
+			"<key>Program</key>",
+			"<string>/path/to/the/program</string>",
+
+			"<key>StandardOutPath</key>",
+			"<string>/dev/null</string>",
+
+			"<key>StandardErrorPath</key>",
+			"<string>/dev/null</string>",
+
+			"<key>ProgramArguments</key>",
+			"<array>",
+			"<string>/path/to/the/program</string>",
+			"<string>--test</string>",
+			"<string>another-arg</string>",
+			"</array>",
+
 			"</dict>",
 			"</plist>",
 		},

internal/daemon/systemd.go

@@ -15,7 +15,7 @@ Description={{.Description}}
 
 [Service]
 Type=simple
-ExecStart={{sq_escape .Program}}
+ExecStart={{sq_escape .Program}}{{range .Arguments}} {{sq_escape .}}{{end}}
 `
 
 type systemd struct {

internal/daemon/systemd_test.go

@@ -101,6 +101,25 @@ var systemdCreateServiceUnitTests = []struct {
 			"ExecStart='/path/to/the/program with a space'",
 		},
 	},
+	{
+		title: "Service unit ExecStart captures args, quoted and escaped",
+		config: &daemon.DaemonConfig{
+			Label:       "test-escape",
+			Description: "Another program description",
+			Program:     "/path/to/the/program with a space",
+			Arguments: []string{
+				"--my-option",
+				"an arg with double quotes \", single quotes ', and spaces!",
+			},
+		},
+		expectedServiceUnitLines: []string{
+			"[Unit]",
+			"Description=Another program description",
+			"[Service]",
+			"Type=simple",
+			"ExecStart='/path/to/the/program with a space' '--my-option' 'an arg with double quotes \", single quotes \\', and spaces!'",
+		},
+	},
 }
 
 func TestSystemd_Create(t *testing.T) {