add a test for maybeParseAsExpression

src/main.test.ts

@@ -1,7 +1,7 @@
 import * as fs from "node:fs/promises";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
-import { main, resetErrors } from "./main.js";
+import { main, maybeParseAsExpression, resetErrors } from "./main.js";
 import { mockError, mockExit, mockLog } from "./test-utils.js";
 
 vi.mock("node:fs/promises");
@@ -61,4 +61,55 @@ describe("main", () => {
  "Operands must be two numbers or two strings.\n[line 1]",
  );
  });
+
+ describe("maybeParseAsExpression", () => {
+ it("should parse an expressions", () => {
+ const error = mockError();
+ expect(maybeParseAsExpression("1 + 2*2")).toMatchInlineSnapshot(`
+ {
+ "kind": "binary",
+ "left": {
+ "kind": "literal",
+ "value": 1,
+ },
+ "operator": {
+ "lexeme": "+",
+ "line": 1,
+ "literal": null,
+ "type": "+",
+ },
+ "right": {
+ "kind": "binary",
+ "left": {
+ "kind": "literal",
+ "value": 2,
+ },
+ "operator": {
+ "lexeme": "*",
+ "line": 1,
+ "literal": null,
+ "type": "*",
+ },
+ "right": {
+ "kind": "literal",
+ "value": 2,
+ },
+ },
+ }
+ `);
+ expect(error).not.toHaveBeenCalled();
+ });
+
+ it("should return null and not log on a statement", () => {
+ const error = mockError();
+ expect(maybeParseAsExpression("1 + 2*2;")).toBeNull();
+ expect(error).not.toHaveBeenCalled();
+ });
+
+ it("should return null and not log on a syntax error", () => {
+ const error = mockError();
+ expect(maybeParseAsExpression("1 + 2*")).toBeNull();
+ expect(error).not.toHaveBeenCalled();
+ });
+ });
 });

src/main.ts

@@ -55,7 +55,7 @@ let throwMode = false;
 
 class ParseError extends Error {}
 
-function maybeParseAsExpression(line: string): Expr | null {
+export function maybeParseAsExpression(line: string): Expr | null {
  throwMode = true;
  try {
  const scanner = new Scanner(line + ";");