Add backslash for escaping

src/utils/argsUtil.ts

@@ -1,66 +1,108 @@
 type ParseError = string
 
+const escapeAtEndError = "args string has escape character (\\) at the end of the string, with nothing to escape.";
+
 /**
  * Parses an argument string with shell-like semantics into a list of arguments.
  * Returns an error only if the argument string is malformed.
  * 
  * - Whitespace is treated as the word separator.
  * - Each word is treated as an argument to be passed to the invocation process.
  * - Single-quotes and double-quotes can be used to escape whitespace characters as literals.
+ * - A backslash followed by a quote can be used (\' or \") to escape quotes as literals.
  * - Null arguments ("" or '') are retained and passed as empty strings.
  *   When a null argument appears as part of a non-null argument, the null argument is removed.
  *   That is, the word -d'' or ''-d becomes -d after word splitting and null argument removal.
  * @param args The string containing arguments to be parsed.
  */
 export function parseArgsString(args: string): string[] | ParseError {
-	let result: string[] = [];
+	let resOrErr: string[] = [];
 	let word: string = "";
 	let bufferedWord: boolean = false;
 
 	for (let i = 0; i < args.length;) {
 		if (args[i] == "'") {
 			let j = i + 1;
-			for (; j < args.length && args[j] != "'"; j++) {
+			let k = i + 1;
+			for (; k < args.length && args[k] != "'";) {
+				if (args[k] == '\\'
+					&& k + 1 < args.length
+					&& (args[k + 1] == "'" || args[k + 1] == '"')) {
+					bufferedWord = true;
+					// buffer everything up to this point
+					word += args.slice(j, k)
+					word += args.charAt(k + 1)
+
+					j = k + 2
+					k = k + 2
+				} else {
+					k++
+				}
 			}
-			if (j >= args.length) {
+			if (k >= args.length) {
 				return "args string has unmatched single quotes ('). starting index: " + i
 			}
 
 			bufferedWord = true;
-			word += args.slice(i + 1, j);
-			i = j + 1;
+			word += args.slice(j, k);
+			i = k + 1;
 		} else if (args[i] == '"') {
 			let j = i + 1;
-			for (; j < args.length && args[j] != '"'; j++) {
+			let k = i + 1;
+			for (; k < args.length && args[k] != '"';) {
+				if (args[k] == '\\'
+					&& k + 1 < args.length
+					&& (args[k + 1] == "'" || args[k + 1] == '"')) {
+					bufferedWord = true;
+					// buffer everything up to this point
+					word += args.slice(j, k)
+					word += args.charAt(k + 1)
+
+					j = k + 2
+					k = k + 2
+				} else {
+					k++;
+				}
 			}
-			if (j >= args.length) {
-				return "args string has unmatched double quotes (\"). starting index: " + i
+			if (k >= args.length) {
+				return 'args string has unmatched double quotes ("). starting index: ' + i
 			}
 
 			bufferedWord = true;
-			word += args.slice(i + 1, j);
-			i = j + 1;
+			word += args.slice(j, k);
+			i = k + 1;
+		} else if (args[i] == '\\'
+			&& i + 1 < args.length
+			&& (args[i + 1] == "'" || args[i + 1] == '"')) {
+			bufferedWord = true;
+			word += args.charAt(i + 1);
+			i = i + 2;
 		} else if (args[i] != ' ') {
 			let j = i + 1;
 			for (; j < args.length
-				&& args[j] != ' ' && args[j] != "'" && args[j] != '"'; j++) {
+				&& args[j] != ' '
+				&& args[j] != "'"
+				&& args[j] != '"'
+				&& args[j] != '\\';
+				j++) {
 			}
 
 			bufferedWord = true;
 			word += args.slice(i, j);
 			i = j;
 		} else if (bufferedWord) { // also true that args[i] == ' '
-			result.push(word);
+			resOrErr.push(word);
 			word = "";
 			bufferedWord = false;
+			i++;
 		} else { // args[i] == ' '
 			i++
 		}
 	}
 
 	if (bufferedWord) {
-		result.push(word);
+		resOrErr.push(word);
 	}
 
-	return result;
+	return resOrErr;
 }

test/unit/util.test.ts

@@ -21,7 +21,7 @@ suite('util tests', () => {
 				want: ['value 1', 'value 2', 'value3', 'value4']
 			},
 			{
-				test: 'InnerQuotes',
+				test: 'SingleSurroundingDoubleQuotes',
 				args: [`' "text" '`],
 				want: [' "text" ']
 			},
@@ -30,14 +30,24 @@ suite('util tests', () => {
 				args: [`" 'text' "`],
 				want: [` 'text' `]
 			},
+			{
+				test: 'EscapedQuotes',
+				args: [`\\'a \\'b \\"c \\"d`],
+				want: [`'a`, `'b`, '"c', '"d']
+			},
+			{
+				test: 'EscapedQuotesInsideQuotes',
+				args: [`'a\\' b\\"'  "\\'c \\"d"`],
+				want: [`a' b"`, `'c "d`]
+			},
 			{
 				test: 'Null',
 				args: [`''`, '""'],
 				want: ['']
 			},
 			{
 				test: 'Empty',
-				args: [' '],
+				args: ['', ' ', '  '],
 				want: [] as string[]
 			},
 			{