miqt-docker: Add more environment variables to customize docker run

cmd/miqt-docker/main.go

@@ -39,6 +39,8 @@ interactive terminal; or one of the following special tasks:
 Environment variables:
   DOCKER           Override the path to docker
   MIQTDOCKER_UID   Run the docker command under a custom uid or uid:gid
+  MIQTDOCKER_FLAGS Add extra flags to the docker command
+  MIQTDOCKER_PERM  Specify volume mount permissions (e.g. 'ro', 'rw', or 'Z')
 
 Available container environments: (use - as wildcard character)
   native (Run natively without docker)
@@ -252,8 +254,24 @@ func getDockerRunArgsForGlob(dockerfiles []fs.DirEntry, containerNameGlob string
 		mountDir = strings.ReplaceAll(mountDir, `\`, `/`)
 	}
 
+	// Extra user-supplied docker flags
+	// Prepopulate some things that the user may want to replace/override
+	if extraFlags := os.Getenv(`MIQTDOCKER_FLAGS`); extraFlags != "" {
+		fullCommand = append(fullCommand, StringFields(extraFlags)...)
+	} else {
+		// Default MIQTDOCKER_FLAGS:
+		// `--security-opt label=disable` - required for SELinux compatibility on Bazzite (#316)
+		fullCommand = append(fullCommand, `--security-opt`, `label=disable`)
+	}
+
+	// Volume mount permissions (e.g. 'rw', 'ro', 'Z')
+	volumeMountPermissions := ``
+	if setPerms := os.Getenv(`MIQTDOCKER_PERM`); setPerms != "" {
+		volumeMountPermissions = `:` + setPerms
+	}
+
 	fullCommand = append(fullCommand,
-		`-v`, basedir+`:`+mountDir,
+		`-v`, basedir+`:`+mountDir+volumeMountPermissions,
 		`-w`, path.Join(mountDir, relCwd),
 
 		// Final standard docker commands

cmd/miqt-docker/stringfields.go

@@ -0,0 +1,58 @@
+package main
+
+// StringFields tokenizes an input string into an array of separate fields. It
+// supports quotes. It doesn't parse escape sequences.
+func StringFields(input string) []string {
+
+	var ret []string = make([]string, 0)
+	var tmp string
+	flush := func() {
+		if len(tmp) > 0 {
+			ret = append(ret, tmp)
+			tmp = ""
+		}
+	}
+
+	type parseState int
+	const (
+		Normal parseState = iota
+		InsideDoubleQuotes
+		InsideSingleQuotes
+	)
+	var state parseState = Normal
+
+	for _, r := range input {
+		if state == Normal {
+			if r == '"' {
+				state = InsideDoubleQuotes
+			} else if r == '\'' {
+				state = InsideSingleQuotes
+			} else if r == ' ' || r == '\t' || r == '\n' || r == '\r' {
+				flush()
+			} else {
+				tmp += string(r)
+			}
+
+		} else if state == InsideDoubleQuotes {
+			if r == '"' {
+				state = Normal // Don't flush yet, might be switching quote types mid-field
+			} else {
+				tmp += string(r)
+			}
+
+		} else if state == InsideSingleQuotes {
+			if r == '\'' {
+				state = Normal
+			} else {
+				tmp += string(r)
+			}
+
+		} else {
+			panic("invalid state") // unreachable
+		}
+	}
+
+	flush() // any incomplete fields
+
+	return ret
+}

cmd/miqt-docker/stringfields_test.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestStringFields(t *testing.T) {
+	type testCase struct {
+		input  string
+		expect []string
+	}
+
+	cases := []testCase{
+		// blank string = no fields
+		{"", []string{}},
+
+		// Spaces are trimmed
+		{" ", []string{}},
+		{"  ", []string{}},
+		{"hello", []string{"hello"}},
+		{"  hello  ", []string{"hello"}},
+
+		// Other types of whitespace
+		{" \t \r hello \n ", []string{"hello"}},
+
+		// Multiple tokens
+		{"hello world", []string{"hello", "world"}},
+
+		// Quotes
+		{`"hello" world`, []string{"hello", "world"}},
+		{`"hello"    'world'`, []string{"hello", "world"}},
+
+		// Switching quote types inside a single token
+		{`"he"'ll'o world`, []string{"hello", "world"}},
+
+		// Leftover unquoted text
+		{`"leftover`, []string{"leftover"}},
+
+		// Real world expected use case
+		{`--security-opt label:disable --user 1000:0`, []string{"--security-opt", "label:disable", "--user", "1000:0"}},
+	}
+
+	for _, tc := range cases {
+		got := StringFields(tc.input)
+
+		if fmt.Sprintf("%#v", got) != fmt.Sprintf("%#v", tc.expect) {
+			t.Errorf("StringFields(%q); got %#v, want %#v", tc.input, got, tc.expect)
+		}
+	}
+}