webstudio/packages/expression/src/expression.test.ts

import { describe, expect, test } from "vitest";
import { parseExpressionAt } from "acorn";
import {
  type Diagnostic,
  getExpressionValueKind,
  isLiteralExpression,
  isValidExpression,
  lintExpression,
  transpileExpression,
  getExpressionIdentifiers,
  generateObjectExpression,
  generateJsonExpression,
  parseJsonExpression,
  parseExpressionObject,
  parseArrayExpression,
  parseDirectPathExpression,
  parseStaticMemberPath,
  parseStringLiteralExpression,
  allowedArrayMethods,
  allowedStringMethods,
} from "./index";

test("validates complete expressions", () => {
  expect(isValidExpression("post.title ?? 'Untitled'")).toBe(true);
  expect(isValidExpression("post.title trailing")).toBe(false);
  expect(isValidExpression("{")).toBe(false);
});

describe("static member paths", () => {
  test.each([
    ["system.params.slug", ["system", "params", "slug"]],
    ['system.params["slug"]', ["system", "params", "slug"]],
    ["system?.params?.slug", ["system", "params", "slug"]],
    ['system?.params?.["slug"]', ["system", "params", "slug"]],
    ["items[0].title", ["items", "0", "title"]],
    ["system.params[slug]", undefined],
    ["system.params.slug ?? fallback", undefined],
    ["system.params.slug trailing", undefined],
    ["system.params.", undefined],
  ])("parses %s", (source, expected) => {
    expect(parseStaticMemberPath(source)).toEqual(expected);
  });
});

describe("direct path expressions", () => {
  test.each([
    "document.frontmatter.author?.name",
    "document?.frontmatter?.author?.name",
    'document.frontmatter?.["author"].name',
    "(document.frontmatter?.author).name",
  ])("preserves the writable location of %s", (expression) => {
    expect(parseDirectPathExpression(expression)).toEqual({
      type: "direct-path",
      expression,
      path: ["document", "frontmatter", "author", "name"],
    });
  });

  test("distinguishes a writable location from a derived expression", () => {
    expect(parseDirectPathExpression("document.frontmatter.title")).toEqual({
      type: "direct-path",
      expression: "document.frontmatter.title",
      path: ["document", "frontmatter", "title"],
    });
    expect(
      parseDirectPathExpression('document.frontmatter.title + "!"')
    ).toBeUndefined();
    expect(
      parseDirectPathExpression("document.frontmatter[fieldName]")
    ).toBeUndefined();
  });
});

describe("string literal expressions", () => {
  test.each([
    ['"assets"', "assets"],
    ["'assets'", undefined],
    [' "assets"', undefined],
    ['"assets" trailing', undefined],
    ["assets", undefined],
  ])("parses %s", (source, expected) => {
    expect(parseStringLiteralExpression(source)).toBe(expected);
  });
});

describe("lint expression", () => {
  const error = (from: number, to: number, message: string): Diagnostic => ({
    from,
    to,
    severity: "error",
    message,
  });

  const warn = (from: number, to: number, message: string): Diagnostic => ({
    from,
    to,
    severity: "warning",
    message,
  });

  test("forbid empty expression", () => {
    expect(lintExpression({ expression: `` })).toEqual([
      error(0, 0, `Expression cannot be empty`),
    ]);
    expect(lintExpression({ expression: `  ` })).toEqual([
      error(0, 0, `Expression cannot be empty`),
    ]);
  });

  test("output parse error as diagnostic", () => {
    expect(lintExpression({ expression: `a + ` })).toEqual([
      error(4, 4, "Unexpected token"),
    ]);
    expect(lintExpression({ expression: `"string" + a)` })).toEqual([
      error(13, 13, "Unexpected token"),
    ]);
  });

  test("restrict expression syntax", () => {
    expect(lintExpression({ expression: `var a = 1` })).toEqual([
      error(0, 0, "Unexpected token"),
    ]);
  });

  test("lint whole expression instead of only first valid part", () => {
    expect(
      lintExpression({ expression: `a""`, availableVariables: new Set(["a"]) })
    ).toEqual([error(1, 1, `Unexpected token`)]);
    expect(
      lintExpression({
        expression: `/movie/{{CollectionItem['title']}}\n`,
        availableVariables: new Set([""]),
      })
    ).toEqual([error(7, 7, `Unexpected token`)]);
  });

  test("supports accessing variable fields", () => {
    expect(
      lintExpression({
        expression: `a.b.c`,
        availableVariables: new Set(["a"]),
      })
    ).toEqual([]);
  });

  test("supports literals", () => {
    expect(
      lintExpression({
        expression: `"" + 0 + true + [] + {}`,
      })
    ).toEqual([]);
  });

  test("supports ternary operator", () => {
    expect(
      lintExpression({
        expression: `true ? false : true`,
      })
    ).toEqual([]);
  });

  test("supports template literals", () => {
    expect(
      lintExpression({
        expression: "`my ${1} template ${'2'}`",
      })
    ).toEqual([]);
    expect(
      lintExpression({
        expression: "`my template",
      })
    ).toEqual([error(1, 1, "Unterminated template")]);
  });

  test("supports parentheses", () => {
    expect(
      lintExpression({
        expression: "(1 + 1) * 2",
      })
    ).toEqual([]);
  });

  test("forbid assignment until enabled", () => {
    expect(
      lintExpression({
        expression: ` a = 1`,
        availableVariables: new Set(["a"]),
      })
    ).toEqual([error(1, 6, "Assignment is not supported in this context")]);
    expect(
      lintExpression({
        expression: ` a = 1`,
        allowAssignment: true,
        availableVariables: new Set(["a"]),
      })
    ).toEqual([]);
  });

  test("lint member assignment targets", () => {
    expect(
      lintExpression({
        expression: ` a[b].c = d`,
        allowAssignment: true,
        availableVariables: new Set(["a", "b", "d"]),
      })
    ).toEqual([]);
    expect(
      lintExpression({
        expression: ` a.b = c`,
        allowAssignment: true,
        availableVariables: new Set(["c"]),
      })
    ).toEqual([warn(1, 2, `"a" is not defined in the scope`)]);
  });

  test("lint assignment operators and targets", () => {
    const assignmentExpressions = [
      ` a = b`,
      ` a += b`,
      ` a -= b`,
      ` a *= b`,
      ` a /= b`,
      ` a %= b`,
      ` a **= b`,
      ` a ||= b`,
      ` a &&= b`,
      ` a ??= b`,
      ` a.b = c`,
      ` a[b] = c`,
      ` a[b].c = d`,
      ` a.b[c.d].e ??= f.g`,
    ];

    for (const expression of assignmentExpressions) {
      expect(
        lintExpression({
          expression,
          allowAssignment: true,
          availableVariables: new Set(["a", "b", "c", "d", "f"]),
        })
      ).toEqual([]);
    }
  });

  test("forbid destructuring assignment", () => {
    expect(
      lintExpression({
        expression: ` ({ a } = b)`,
        allowAssignment: true,
        availableVariables: new Set(["b"]),
      })
    ).toEqual([error(2, 7, "Destructuring assignment is not supported")]);
    expect(
      lintExpression({
        expression: ` [a] = b`,
        allowAssignment: true,
        availableVariables: new Set(["b"]),
      })
    ).toEqual([error(1, 4, "Destructuring assignment is not supported")]);
    expect(
      lintExpression({
        expression: ` ({ nested: a } = b)`,
        allowAssignment: true,
        availableVariables: new Set(["b"]),
      })
    ).toEqual([error(2, 15, "Destructuring assignment is not supported")]);
  });

  test("forbid unavailable variables", () => {
    expect(
      lintExpression({ expression: ` a = b + 1`, allowAssignment: true })
    ).toEqual([
      warn(5, 6, `"b" is not defined in the scope`),
      warn(1, 2, `"a" is not defined in the scope`),
    ]);
    expect(
      lintExpression({
        expression: ` a = b + 1`,
        allowAssignment: true,
        availableVariables: new Set(["a", "b"]),
      })
    ).toEqual([]);
  });

  test(`forbid "this" keyword`, () => {
    expect(lintExpression({ expression: ` this.name` })).toEqual([
      error(1, 5, `"this" keyword is not supported`),
    ]);
  });

  test("forbid functions", () => {
    expect(
      lintExpression({
        expression: ` function(){} + (() => {}) + fn()`,
        availableVariables: new Set(["fn"]),
      })
    ).toEqual([
      error(1, 13, "Functions are not supported"),
      error(17, 25, "Functions are not supported"),
      error(29, 33, `"fn" function is not supported`),
    ]);
  });

  test("forbid increment and decrement", () => {
    expect(
      lintExpression({
        expression: ` ++i + --j`,
        availableVariables: new Set(["j", "i"]),
      })
    ).toEqual([
      error(1, 4, "Increment and decrement are not supported"),
      error(7, 10, "Increment and decrement are not supported"),
    ]);
  });

  test("forbid sequence expression", () => {
    expect(lintExpression({ expression: ` 1, 2, 3` })).toEqual([
      error(1, 8, "Only single expression is supported"),
    ]);
  });

  test(`forbid "yield" keyword`, () => {
    expect(lintExpression({ expression: ` yield 1` })).toEqual([
      error(1, 1, `The keyword 'yield' is reserved`),
    ]);
  });

  test("forbid tagged template", () => {
    expect(
      lintExpression({
        expression: " tag`hello`",
        availableVariables: new Set(["tag"]),
      })
    ).toEqual([error(1, 11, "Tagged template is not supported")]);
  });

  test("forbid classes", () => {
    expect(
      lintExpression({
        expression: ` class {} + new MyClass()`,
        availableVariables: new Set(["MyClass"]),
      })
    ).toEqual([
      error(1, 9, "Classes are not supported"),
      error(12, 25, "Classes are not supported"),
    ]);
  });

  test("forbid imports", () => {
    expect(
      lintExpression({ expression: ` import("") + import.meta.url` })
    ).toEqual([
      error(1, 11, "Imports are not supported"),
      error(14, 25, "Imports are not supported"),
    ]);
  });

  test(`forbid "await" keyword`, () => {
    expect(lintExpression({ expression: ` await 1` })).toEqual([
      error(1, 8, `"await" keyword is not supported`),
    ]);
  });

  test.each([
    "toLowerCase",
    "replace",
    "split",
    "at",
    "slice",
    "endsWith",
    "includes",
    "startsWith",
    "toString",
    "toUpperCase",
    "toLocaleLowerCase",
    "toLocaleUpperCase",
  ])("allow safe string method: %s", (method) => {
    expect(
      lintExpression({
        expression: `title.${method}()`,
        availableVariables: new Set(["title"]),
      })
    ).toEqual([]);
  });

  test.each(["at", "includes", "join", "slice", "toString"])(
    "allow safe array method: %s",
    (method) => {
      expect(
        lintExpression({
          expression: `arr.${method}()`,
          availableVariables: new Set(["arr"]),
        })
      ).toEqual([]);
    }
  );

  test("allow supported methods on known native-compatible receivers", () => {
    expect(
      lintExpression({
        expression: `title.split("").toString()`,
        availableVariables: new Set(["title"]),
        variableValues: new Map([["title", "Test"]]),
      })
    ).toEqual([]);
    expect(
      lintExpression({
        expression: `arr.join("").split("").toString()`,
        availableVariables: new Set(["arr"]),
        variableValues: new Map([["arr", ["T", "e", "s", "t"]]]),
      })
    ).toEqual([]);
    expect(
      lintExpression({
        expression: `count.toString() + flag.toString() + object.toString()`,
        availableVariables: new Set(["count", "flag", "object"]),
        variableValues: new Map<string, unknown>([
          ["count", 2],
          ["flag", true],
          ["object", {}],
        ]),
      })
    ).toEqual([]);
    expect(
      lintExpression({
        expression: `title.replace("e", "a").toLowerCase()`,
        availableVariables: new Set(["title"]),
      })
    ).toEqual([]);
    expect(
      lintExpression({
        expression: `arr.join("").toLowerCase()`,
        availableVariables: new Set(["arr"]),
      })
    ).toEqual([]);
  });

  test("forbid supported method names on known native-incompatible receivers", () => {
    expect(
      lintExpression({
        expression: `arr.split()`,
        availableVariables: new Set(["arr"]),
        variableValues: new Map([["arr", []]]),
      }).map((diagnostic) => diagnostic.message)
    ).toEqual([`"split" function is not supported`]);
    expect(
      lintExpression({
        expression: `title.join()`,
        availableVariables: new Set(["title"]),
        variableValues: new Map([["title", "Test"]]),
      }).map((diagnostic) => diagnostic.message)
    ).toEqual([`"join" function is not supported`]);
    expect(
      lintExpression({
        expression: `[1, 2, 3].toLowerCase()`,
      }).map((diagnostic) => diagnostic.message)
    ).toEqual([`"toLowerCase" function is not supported`]);
    expect(
      lintExpression({
        expression: `"Test".join()`,
      }).map((diagnostic) => diagnostic.message)
    ).toEqual([`"join" function is not supported`]);
    expect(
      lintExpression({
        expression: `title.split("").toLowerCase()`,
        availableVariables: new Set(["title"]),
      }).map((diagnostic) => diagnostic.message)
    ).toEqual([`"toLowerCase" function is not supported`]);
    expect(
      lintExpression({
        expression: `arr.join("").join()`,
        availableVariables: new Set(["arr"]),
      }).map((diagnostic) => diagnostic.message)
    ).toEqual([`"join" function is not supported`]);
    expect(
      lintExpression({
        expression: `null.toString() + undefined.toString()`,
      }).map((diagnostic) => diagnostic.message)
    ).toEqual([
      `"toString" function is not supported`,
      `"undefined" is not defined in the scope`,
      `"toString" function is not supported`,
    ]);
  });

  test("allow chained string methods", () => {
    expect(
      lintExpression({
        expression: `title.toLowerCase().replace(" ", "-").split("-")`,
        availableVariables: new Set(["title"]),
      })
    ).toEqual([]);
  });

  test("forbid unsafe method calls", () => {
    expect(
      lintExpression({
        expression: `arr.pop()`,
        availableVariables: new Set(["arr"]),
      })
    ).toEqual([error(0, 9, `"pop" function is not supported`)]);
    expect(
      lintExpression({
        expression: `obj.push(1)`,
        availableVariables: new Set(["obj"]),
      })
    ).toEqual([error(0, 11, `"push" function is not supported`)]);
  });

  test("forbid standalone function calls", () => {
    expect(
      lintExpression({
        expression: `func()`,
        availableVariables: new Set(["func"]),
      })
    ).toEqual([error(0, 6, `"func" function is not supported`)]);
  });

  test("visits supported unary, logical, and optional-chain syntax", () => {
    expect(
      lintExpression({
        expression: `!value || record?.enabled`,
        availableVariables: new Set(["value", "record"]),
      })
    ).toEqual([]);
  });

  test("rejects calls without a named callee", () => {
    expect(
      lintExpression({ expression: `(function () {})()` }).map(
        ({ message }) => message
      )
    ).toEqual(["Functions are not supported", "Functions are not supported"]);
  });
});

describe("expression value kinds", () => {
  test.each([
    ["[]", "array"],
    ["1n", "bigint"],
    ["true", "boolean"],
    ["undefined", "nullish"],
    ["null", "nullish"],
    ["1", "number"],
    ["{}", "object"],
    ['"text"', "string"],
    ["`text`", "string"],
    ['"text" + value', "string"],
    ['"text" /* trailing comment */', "string"],
    ["value +", "unknown"],
    ['"text" trailing', "unknown"],
  ] as const)("classifies %s as %s", (expression, kind) => {
    expect(getExpressionValueKind({ expression })).toBe(kind);
  });

  test("uses map and record variable values", () => {
    expect(
      getExpressionValueKind({
        expression: "value",
        variableValues: new Map([["value", [1, 2]]]),
      })
    ).toBe("array");
    expect(
      getExpressionValueKind({
        expression: "value",
        variableValues: { value: "text" },
      })
    ).toBe("string");
    expect(
      getExpressionValueKind({
        expression: "missing",
        variableValues: new Map(),
      })
    ).toBe("unknown");
    expect(
      getExpressionValueKind({
        expression: "missing",
        variableValues: {},
      })
    ).toBe("unknown");
    expect(
      getExpressionValueKind({
        expression: "callback",
        variableValues: { callback: () => undefined },
      })
    ).toBe("unknown");
  });

  test("infers supported method return kinds", () => {
    expect(getExpressionValueKind({ expression: '"text".split("")' })).toBe(
      "array"
    );
    expect(getExpressionValueKind({ expression: "[].join(',')" })).toBe(
      "string"
    );
    expect(
      getExpressionValueKind({ expression: "unknownValue.split('')" })
    ).toBe("array");
    expect(
      getExpressionValueKind({ expression: "unknownValue.join(',')" })
    ).toBe("string");
    expect(getExpressionValueKind({ expression: "unknownValue.at(0)" })).toBe(
      "unknown"
    );
    expect(getExpressionValueKind({ expression: "unknownValue.slice()" })).toBe(
      "unknown"
    );
    expect(getExpressionValueKind({ expression: "true.toString()" })).toBe(
      "string"
    );
    expect(getExpressionValueKind({ expression: "true.slice()" })).toBe(
      "unknown"
    );
    expect(getExpressionValueKind({ expression: "value?.name" })).toBe(
      "unknown"
    );
  });
});

test("check simple literals", () => {
  expect(isLiteralExpression(`""`)).toEqual(true);
  expect(isLiteralExpression(`''`)).toEqual(true);
  expect(isLiteralExpression(`0`)).toEqual(true);
  expect(isLiteralExpression(`true`)).toEqual(true);
  expect(isLiteralExpression(`[]`)).toEqual(true);
  expect(isLiteralExpression(`{}`)).toEqual(true);
  expect(isLiteralExpression(`undefined`)).toEqual(true);
  expect(isLiteralExpression(`"" + ""`)).toEqual(false);
  expect(isLiteralExpression(`{}.field`)).toEqual(false);
  expect(isLiteralExpression(`variable`)).toEqual(false);
  expect(isLiteralExpression(`1 trailing`)).toEqual(false);
  expect(isLiteralExpression(``)).toEqual(false);
});

test("check complex objects and arrays", () => {
  expect(isLiteralExpression(`[1, 2, 3]`)).toEqual(true);
  expect(isLiteralExpression(`[1, 2, variable]`)).toEqual(false);
  expect(isLiteralExpression(`[...variable]`)).toEqual(false);
  expect(isLiteralExpression(`{ param: 0 }`)).toEqual(true);
  expect(isLiteralExpression(`{ "param": 0 }`)).toEqual(true);
  expect(isLiteralExpression(`{ param: variable }`)).toEqual(false);
  expect(isLiteralExpression(`{ ["param"]: 0 }`)).toEqual(true);
  expect(isLiteralExpression(`{ [variable]: 0 }`)).toEqual(false);
  expect(isLiteralExpression(`{ ...variable }`)).toEqual(false);
});

describe("get expression identifiers", () => {
  test("find all identifiers", () => {
    expect(getExpressionIdentifiers("a = b * c.d")).toEqual(
      new Set(["a", "b", "c"])
    );
  });

  test("find identifiers in assignment targets", () => {
    expect(getExpressionIdentifiers("a[b].c = d.e")).toEqual(
      new Set(["a", "b", "d"])
    );
    expect(getExpressionIdentifiers("a.b[c.d].e ??= f.g")).toEqual(
      new Set(["a", "c", "f"])
    );
  });

  test("deduplicate identifiers", () => {
    expect(getExpressionIdentifiers("a = a + b")).toEqual(new Set(["a", "b"]));
  });

  test("not fail when invalid syntax", () => {
    expect(getExpressionIdentifiers("")).toEqual(new Set());
    expect(getExpressionIdentifiers("a = a +")).toEqual(new Set());
    expect(getExpressionIdentifiers("a trailing")).toEqual(new Set());
  });
});

describe("transpile expression", () => {
  const expectTranspiledExpressionToMatchNative = (expression: string) => {
    const nativeResult = new Function(`return (${expression})`)();
    const transpiledResult = new Function(
      `return (${transpileExpression({ expression, executable: true })})`
    )();
    expect(transpiledResult).toEqual(nativeResult);
  };

  test("preserve spaces and parentheses", () => {
    expect(
      transpileExpression({ expression: " 1 + (2 + 3) ", executable: true })
    ).toEqual(" 1 + (2 + 3) ");
  });

  test("add optional chaining with dot syntax", () => {
    expect(
      transpileExpression({ expression: "a.b . c", executable: true })
    ).toEqual("a?.b ?. c");
  });

  test("add optional chaining with computed", () => {
    expect(
      transpileExpression({ expression: "a['b'] [c]", executable: true })
    ).toEqual("a?.['b'] ?.[c]");
  });

  test("skip optional chaining", () => {
    expect(
      transpileExpression({ expression: "a?.['b']?.c", executable: true })
    ).toEqual("a?.['b']?.c");
  });

  test("skip optional chaining in assignment targets", () => {
    expect(
      transpileExpression({ expression: "a.b = c.d", executable: true })
    ).toEqual("a.b = c?.d");
    expect(
      transpileExpression({ expression: "a[b.c].d = e.f", executable: true })
    ).toEqual("a[b?.c].d = e?.f");
  });

  test("skip optional chaining in assignment targets for all assignment operators", () => {
    const operators = [
      "=",
      "+=",
      "-=",
      "*=",
      "/=",
      "%=",
      "**=",
      "||=",
      "&&=",
      "??=",
    ];

    for (const operator of operators) {
      const expression = `a.b ${operator} c.d`;
      const transpiled = transpileExpression({ expression, executable: true });
      expect(transpiled).toEqual(`a.b ${operator} c?.d`);
      expect(() =>
        parseExpressionAt(transpiled, 0, { ecmaVersion: "latest" })
      ).not.toThrow();
    }
  });

  test("transpile executable assignment expressions", () => {
    const cases = [
      ["a.b = c.d", "a.b = c?.d"],
      ["a[b] = c.d", "a[b] = c?.d"],
      ["a[b.c] = d.e", "a[b?.c] = d?.e"],
      ["a[b.c].d = e.f", "a[b?.c].d = e?.f"],
      ["a.b[c.d].e ??= f.g", "a.b[c?.d].e ??= f?.g"],
    ] as const;

    for (const [expression, expected] of cases) {
      const transpiled = transpileExpression({ expression, executable: true });
      expect(transpiled).toEqual(expected);
      expect(() =>
        parseExpressionAt(transpiled, 0, { ecmaVersion: "latest" })
      ).not.toThrow();
    }
  });

  test("replace variable", () => {
    expect(
      transpileExpression({
        expression: "(a + c) * b",
        replaceVariable: (identifier) => identifier + "_1",
      })
    ).toEqual("(a_1 + c_1) * b_1");
    expect(
      transpileExpression({
        expression: "a = c",
        replaceVariable: (identifier) => identifier + "_1",
      })
    ).toEqual("a_1 = c_1");
  });

  test("skip identifiers in nested member expressions", () => {
    const identifiers: string[] = [];
    const transpiled = transpileExpression({
      expression: "a.b + c.d * e[f]",
      replaceVariable: (identifier) => {
        identifiers.push(identifier);
        return identifier + "_1";
      },
    });
    expect(identifiers).toEqual(["a", "c", "e", "f"]);
    expect(transpiled).toEqual("a_1.b + c_1.d * e_1[f_1]");
  });

  test("inform identifier is an assignee", () => {
    const replaceVariable = (identifier: string, assignee: boolean) => {
      const suffix = assignee ? "_assignee" : "_assigner";
      return identifier + suffix;
    };

    const cases = [
      ["a = b", "a_assignee = b_assigner"],
      ["a += b", "a_assignee += b_assigner"],
      ["a ||= b", "a_assignee ||= b_assigner"],
      ["a ??= b", "a_assignee ??= b_assigner"],
      ["a.b = c", "a_assignee.b = c_assigner"],
      ["a[b] = c", "a_assignee[b_assigner] = c_assigner"],
      ["a[b].c = d", "a_assignee[b_assigner].c = d_assigner"],
      ["a.b[c.d].e ??= f.g", "a_assignee.b[c_assigner.d].e ??= f_assigner.g"],
    ] as const;

    for (const [expression, expected] of cases) {
      expect(transpileExpression({ expression, replaceVariable })).toEqual(
        expected
      );
    }
  });

  test("transpile object literal without changes", () => {
    expect(
      transpileExpression({
        expression: `{ ...name }`,
      })
    ).toEqual(`{ ...name }`);
  });

  test("transpiles a parenthesized object expression", () => {
    expect(
      transpileExpression({
        expression: "({ value: $ws$system.origin })",
        replaceVariable: (identifier) =>
          identifier === "$ws$system" ? "system" : identifier,
      })
    ).toEqual("({ value: system.origin })");
  });

  test("output more readable syntax error", () => {
    let errorString = "";
    try {
      transpileExpression({ expression: `` });
    } catch (error) {
      errorString = (error as Error).message;
    }
    expect(errorString).toEqual(`Unexpected token (1:0) in ""`);
  });

  test("rejects content after the expression", () => {
    expect(() => transpileExpression({ expression: "value trailing" })).toThrow(
      'Unexpected content after expression in "value trailing"'
    );
  });

  test("transpile string methods with optional chaining", () => {
    expect(
      transpileExpression({
        expression: "title.toLowerCase()",
        executable: true,
      })
    ).toEqual("title?.toLowerCase?.()");
    expect(
      transpileExpression({
        expression: "user.name.replace(' ', '-')",
        executable: true,
      })
    ).toEqual("user?.name?.replace?.(' ', '-')");
    expect(
      transpileExpression({
        expression: "data.title.split('-')",
        executable: true,
      })
    ).toEqual("data?.title?.split?.('-')");
  });

  test("preserve native behavior for all supported string methods", () => {
    const expressionsByMethod = {
      at: `"Hello".at(1)`,
      endsWith: `"Hello".endsWith("lo")`,
      includes: `"Hello".includes("ell")`,
      replace: `"Hello".replace("l", "x")`,
      slice: `"Hello".slice(1, 4)`,
      split: `"Hello".split("l")`,
      startsWith: `"Hello".startsWith("He")`,
      toLocaleLowerCase: `"Hello".toLocaleLowerCase()`,
      toLocaleUpperCase: `"Hello".toLocaleUpperCase()`,
      toLowerCase: `"Hello".toLowerCase()`,
      toString: `"Hello".toString()`,
      toUpperCase: `"Hello".toUpperCase()`,
    };

    expect(new Set(Object.keys(expressionsByMethod))).toEqual(
      allowedStringMethods
    );
    for (const expression of Object.values(expressionsByMethod)) {
      expectTranspiledExpressionToMatchNative(expression);
    }
    expectTranspiledExpressionToMatchNative(`"Test".split(2).toString()`);
  });

  test("preserve native behavior for all supported array methods", () => {
    const expressionsByMethod = {
      at: `["a", "b", "c"].at(1)`,
      includes: `["a", "b", "c"].includes("b")`,
      join: `["a", "b", "c"].join("-")`,
      slice: `["a", "b", "c"].slice(1, 3)`,
      toString: `["a", "b", "c"].toString()`,
    };

    expect(new Set(Object.keys(expressionsByMethod))).toEqual(
      allowedArrayMethods
    );
    for (const expression of Object.values(expressionsByMethod)) {
      expectTranspiledExpressionToMatchNative(expression);
    }
  });

  test("transpile chained string methods with optional chaining", () => {
    expect(
      transpileExpression({
        expression: "title.toLowerCase().replace(/\\s+/g, '-')",
        executable: true,
      })
    ).toEqual("title?.toLowerCase?.()?.replace?.(/\\s+/g, '-')");
    expect(
      transpileExpression({
        expression: "user.name.toLowerCase().replace(' ', '-').split('-')",
        executable: true,
      })
    ).toEqual("user?.name?.toLowerCase?.()?.replace?.(' ', '-')?.split?.('-')");
  });

  test("transpile array methods with optional chaining", () => {
    expect(
      transpileExpression({
        expression: "items.map(item => item.id)",
        executable: true,
      })
    ).toEqual("items?.map?.(item => item?.id)");
  });

  test("transpile nested method calls with optional chaining", () => {
    expect(
      transpileExpression({
        expression: "obj.method().prop.anotherMethod()",
        executable: true,
      })
    ).toEqual("obj?.method?.()?.prop?.anotherMethod?.()");
  });

  test("preserve existing optional chaining", () => {
    expect(
      transpileExpression({
        expression: "obj?.method?.()",
        executable: true,
      })
    ).toEqual("obj?.method?.()");
    expect(
      transpileExpression({
        expression: "obj?.prop?.method?.()",
        executable: true,
      })
    ).toEqual("obj?.prop?.method?.()");
  });
});

describe("object expression transformations", () => {
  test("parse complete object expression", () => {
    expect(
      parseExpressionObject(
        "{ value: system.params.slug, limit: pageSize ?? 20 }"
      )
    ).toEqual(
      new Map([
        ["value", "system.params.slug"],
        ["limit", "pageSize ?? 20"],
      ])
    );
    expect(parseExpressionObject("({ value: 1 })")).toEqual(
      new Map([["value", "1"]])
    );
    expect(parseExpressionObject("(({ value: 1 }))")).toEqual(
      new Map([["value", "1"]])
    );
    expect(parseExpressionObject("{} trailing")).toBeUndefined();
    expect(parseExpressionObject("({}) trailing")).toBeUndefined();
    expect(parseExpressionObject("{")).toBeUndefined();
    expect(parseExpressionObject("0")).toBeUndefined();
    expect(parseExpressionObject("{ value: 1, ...other }")).toBeUndefined();
    expect(parseExpressionObject("{ [value]: 1 }")).toBeUndefined();
    expect(parseExpressionObject('{ "quoted-key": 1 }')).toEqual(
      new Map([["quoted-key", "1"]])
    );
    expect(parseExpressionObject("{ 1: true }")).toBeUndefined();
    expect(parseExpressionObject("{ value: 1, value: 2 }")).toBeUndefined();
  });

  test("parse array expression", () => {
    expect(parseArrayExpression(`[0, "", $c + 1]`)).toEqual([
      "0",
      '""',
      "$c + 1",
    ]);
    expect(parseArrayExpression("0")).toBeUndefined();
    expect(parseArrayExpression("[...items]")).toBeUndefined();
    expect(parseArrayExpression("[")).toBeUndefined();
    expect(parseArrayExpression("[1] trailing")).toBeUndefined();
  });

  test("format object expression", () => {
    expect(
      generateObjectExpression(
        new Map([
          ["a", `0`],
          ["b-c", `""`],
          ["d", `$d`],
          ["default", `true`],
          ["$value", `null`],
          ["invalid key", `false`],
        ])
      )
    ).toMatchInlineSnapshot(`
    "{
      a: 0,
      "b-c": "",
      d: $d,
      default: true,
      $value: null,
      "invalid key": false,
    }"
    `);
  });

  test("format empty object expression", () => {
    expect(generateObjectExpression(new Map())).toMatchInlineSnapshot(`
    "{
    }"
    `);
  });

  test("format JSON as readable JavaScript expression source", () => {
    expect(
      generateJsonExpression({
        query: {
          sort: [{ field: ["properties", "date"], direction: "desc" }],
          "file-content": null,
        },
      })
    ).toMatchInlineSnapshot(`
      "{
        query: {
          sort: [{
            field: [\"properties\", \"date\"],
            direction: \"desc\",
          }],
          \"file-content\": null,
        },
      }"
    `);
    expect(() => generateJsonExpression(undefined)).toThrow();
    expect(() => generateJsonExpression(new Date())).toThrow();
    const source = generateJsonExpression({
      enabled: true,
      count: -2,
      values: [null, "value"],
    });
    expect(parseJsonExpression(source)).toEqual({
      enabled: true,
      count: -2,
      values: [null, "value"],
    });
    expect(parseJsonExpression("{ value: dynamic }")).toBeUndefined();
    expect(parseJsonExpression("{ value: 1, value: 2 }")).toBeUndefined();
    expect(parseJsonExpression("{ value: -1e999 }")).toBeUndefined();
    expect(parseJsonExpression('{ "quoted": true }')).toEqual({
      quoted: true,
    });
    expect(parseJsonExpression(undefined)).toBeUndefined();
    expect(parseJsonExpression("true trailing")).toBeUndefined();
    expect(parseJsonExpression("{")).toBeUndefined();
    for (const invalid of [
      "/pattern/",
      "1n",
      "[dynamic]",
      "[,]",
      "[...values]",
      "{ ...value }",
      "{ [key]: 1 }",
      "{ method() {} }",
      "{ value }",
      "{ 1: true }",
    ]) {
      expect(parseJsonExpression(invalid), invalid).toBeUndefined();
    }
  });
});