Fix ANTLR4 JS binding to throw on syntax errors instead of returning partial trees

bnf/atsds_bnf/index.mjs

@@ -1,11 +1,17 @@
-import { InputStream, CommonTokenStream } from "antlr4";
+import { InputStream, CommonTokenStream, ErrorListener } from "antlr4";
 import DspLexer from "./DspLexer.js";
 import DspParser from "./DspParser.js";
 import DspVisitor from "./DspVisitor.js";
 import DsLexer from "./DsLexer.js";
 import DsParser from "./DsParser.js";
 import DsVisitor from "./DsVisitor.js";
 
+class ThrowingErrorListener extends ErrorListener {
+    syntaxError(recognizer, offendingSymbol, line, column, msg, e) {
+        throw new Error(`line ${line}:${column} ${msg}`);
+    }
+}
+
 class ParseVisitor extends DspVisitor {
     visitRule_pool(ctx) {
         return ctx
@@ -104,8 +110,12 @@ class UnparseVisitor extends DsVisitor {
 export function parse(input) {
     const chars = new InputStream(input);
     const lexer = new DspLexer(chars);
+    lexer.removeErrorListeners();
+    lexer.addErrorListener(new ThrowingErrorListener());
     const tokens = new CommonTokenStream(lexer);
     const parser = new DspParser(tokens);
+    parser.removeErrorListeners();
+    parser.addErrorListener(new ThrowingErrorListener());
     const tree = parser.rule_pool();
     const visitor = new ParseVisitor();
     return visitor.visit(tree);
@@ -114,8 +124,12 @@ export function parse(input) {
 export function unparse(input) {
     const chars = new InputStream(input);
     const lexer = new DsLexer(chars);
+    lexer.removeErrorListeners();
+    lexer.addErrorListener(new ThrowingErrorListener());
     const tokens = new CommonTokenStream(lexer);
     const parser = new DsParser(tokens);
+    parser.removeErrorListeners();
+    parser.addErrorListener(new ThrowingErrorListener());
     const tree = parser.rule_pool();
     const visitor = new UnparseVisitor();
     return visitor.visit(tree);

bnf/tests/test_parse_unparse.mjs

@@ -143,3 +143,33 @@ test("roundtrip_unparse_parse", () => {
     const ds_result = parse(dsp_intermediate);
     expect(ds_result).toBe(ds_original);
 });
+
+test("parse_error_missing_closing_parenthesis", () => {
+    // Test that parse throws error on missing closing parenthesis
+    const dsp_input = "(a + b -> c";
+    expect(() => parse(dsp_input)).toThrow(/line 1:7 no viable alternative/);
+});
+
+test("parse_error_bad_syntax", () => {
+    // Test that parse throws error on bad syntax
+    const dsp_input = "a b c -> -> d";
+    expect(() => parse(dsp_input)).toThrow(/line 1:2 mismatched input/);
+});
+
+test("parse_error_malformed_parentheses", () => {
+    // Test that parse throws error on malformed parentheses
+    const dsp_input = "()()()";
+    expect(() => parse(dsp_input)).toThrow(/line 1:1 no viable alternative/);
+});
+
+test("unparse_error_incomplete_binary", () => {
+    // Test that unparse throws error on incomplete binary expression
+    const ds_input = "(binary";
+    expect(() => unparse(ds_input)).toThrow(/line 1:7 mismatched input/);
+});
+
+test("unparse_error_malformed_function", () => {
+    // Test that unparse throws error on malformed function
+    const ds_input = "(function";
+    expect(() => unparse(ds_input)).toThrow(/line 1:9 mismatched input/);
+});