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merged 2 commits into from
Nov 5, 2025
Merged

reject double dot after optional chaining operator, etc. #3585

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75577fc
reject double dot after optional chaining operator
Oct 31, 2025
0ad1212
fix: three additional problems with optional chaining
gwhitney Nov 1, 2025
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29 changes: 22 additions & 7 deletions src/expression/node/FunctionNode.js
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Original file line number Diff line number Diff line change
Expand Up @@ -95,7 +95,7 @@ export const createFunctionNode = /* #__PURE__ */ factory(name, dependencies, ({
* the arguments, typically a SymbolNode or AccessorNode
* @param {./Node[]} args
*/
constructor (fn, args) {
constructor (fn, args, optional) {
super()
if (typeof fn === 'string') {
fn = new SymbolNode(fn)
Expand All @@ -107,9 +107,14 @@ export const createFunctionNode = /* #__PURE__ */ factory(name, dependencies, ({
throw new TypeError(
'Array containing Nodes expected for parameter "args"')
}
const optionalType = typeof optional
if (!(optionalType === 'undefined' || optionalType === 'boolean')) {
throw new TypeError('optional flag, if specified, must be boolean')
}

this.fn = fn
this.args = args || []
this.optional = !!optional
}

// readonly property name
Expand Down Expand Up @@ -137,7 +142,8 @@ export const createFunctionNode = /* #__PURE__ */ factory(name, dependencies, ({
_compile (math, argNames) {
// compile arguments
const evalArgs = this.args.map((arg) => arg._compile(math, argNames))
const fromOptionalChaining = isAccessorNode(this.fn) && this.fn.optionalChaining
const fromOptionalChaining = this.optional ||
(isAccessorNode(this.fn) && this.fn.optionalChaining)

if (isSymbolNode(this.fn)) {
const name = this.fn.name
Expand All @@ -153,12 +159,14 @@ export const createFunctionNode = /* #__PURE__ */ factory(name, dependencies, ({
value = scope.get(name)
} else if (name in math) {
value = getSafeProperty(math, name)
} else {
return FunctionNode.onUndefinedFunction(name)
}
if (typeof value === 'function') {
} else if (fromOptionalChaining) value = undefined
else return FunctionNode.onUndefinedFunction(name)

if (typeof value === 'function' ||
(fromOptionalChaining && value === undefined)) {
return value
}

throw new TypeError(
`'${name}' is not a function; its value is:\n ${strin(value)}`
)
Expand All @@ -185,17 +193,20 @@ export const createFunctionNode = /* #__PURE__ */ factory(name, dependencies, ({
switch (evalArgs.length) {
case 0: return function evalFunctionNode (scope, args, context) {
const fn = resolveFn(scope)
if (fromOptionalChaining && fn === undefined) return undefined
return fn()
}
case 1: return function evalFunctionNode (scope, args, context) {
const fn = resolveFn(scope)
if (fromOptionalChaining && fn === undefined) return undefined
const evalArg0 = evalArgs[0]
return fn(
evalArg0(scope, args, context)
)
}
case 2: return function evalFunctionNode (scope, args, context) {
const fn = resolveFn(scope)
if (fromOptionalChaining && fn === undefined) return undefined
const evalArg0 = evalArgs[0]
const evalArg1 = evalArgs[1]
return fn(
Expand All @@ -205,6 +216,7 @@ export const createFunctionNode = /* #__PURE__ */ factory(name, dependencies, ({
}
default: return function evalFunctionNode (scope, args, context) {
const fn = resolveFn(scope)
if (fromOptionalChaining && fn === undefined) return undefined
const values = evalArgs.map((evalArg) => evalArg(scope, args, context))
return fn(...values)
}
Expand All @@ -214,6 +226,7 @@ export const createFunctionNode = /* #__PURE__ */ factory(name, dependencies, ({
const rawArgs = this.args
return function evalFunctionNode (scope, args, context) {
const fn = getSafeProperty(args, name)
if (fromOptionalChaining && fn === undefined) return undefined
if (typeof fn !== 'function') {
throw new TypeError(
`Argument '${name}' was not a function; received: ${strin(fn)}`
Expand Down Expand Up @@ -245,7 +258,8 @@ export const createFunctionNode = /* #__PURE__ */ factory(name, dependencies, ({
const object = evalObject(scope, args, context)

// Optional chaining: if the base object is nullish, short-circuit to undefined
if (fromOptionalChaining && object == null) {
if (fromOptionalChaining &&
(object == null || object[prop] === undefined)) {
return undefined
}

Expand All @@ -270,6 +284,7 @@ export const createFunctionNode = /* #__PURE__ */ factory(name, dependencies, ({

return function evalFunctionNode (scope, args, context) {
const fn = evalFn(scope, args, context)
if (fromOptionalChaining && fn === undefined) return undefined
if (typeof fn !== 'function') {
throw new TypeError(
`Expression '${fnExpr}' did not evaluate to a function; value is:` +
Expand Down
41 changes: 12 additions & 29 deletions src/expression/parse.js
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Original file line number Diff line number Diff line change
Expand Up @@ -685,6 +685,9 @@ export const createParse = /* #__PURE__ */ factory(name, dependencies, ({
return new AssignmentNode(new SymbolNode(name), value)
} else if (isAccessorNode(node)) {
// parse a matrix subset assignment like 'A[1,2] = 4'
if (node.optionalChaining) {
throw createSyntaxError(state, 'Cannot assign to optional chain')
}
getTokenSkipNewline(state)
value = parseAssignment(state)
return new AssignmentNode(node.object, node.index, value)
Expand Down Expand Up @@ -1396,44 +1399,21 @@ export const createParse = /* #__PURE__ */ factory(name, dependencies, ({
optional = true
// consume the '?.' token
getToken(state)

// Special case: property access via dot-notation following optional chaining (obj?.foo)
// After consuming '?.', the dot is already consumed as part of the token,
// so the next token is the property name itself. Handle that here.
const isPropertyNameAfterOptional = (!types || types.includes('.')) && (
state.tokenType === TOKENTYPE.SYMBOL ||
(state.tokenType === TOKENTYPE.DELIMITER && state.token in NAMED_DELIMITERS)
)
if (isPropertyNameAfterOptional) {
params = []
params.push(new ConstantNode(state.token))
getToken(state)
const dotNotation = true
node = new AccessorNode(node, new IndexNode(params, dotNotation), true)
// Continue parsing, allowing more chaining after this accessor
continue
}
// Otherwise, fall through to allow patterns like obj?.[...]
}

// If the next token does not start an accessor, we're done
const hasNextAccessor =
(state.token === '(' || state.token === '[' || state.token === '.') &&
(!types || types.includes(state.token))

if (!hasNextAccessor) {
// A dangling '?.' without a following accessor is a syntax error
if (optional) {
throw createSyntaxError(state, 'Unexpected operator ?.')
}
if (!(optional || hasNextAccessor)) {
break
}

params = []

if (state.token === '(') {
if (isSymbolNode(node) || isAccessorNode(node)) {
// function invocation like fn(2, 3) or obj.fn(2, 3)
if (optional || isSymbolNode(node) || isAccessorNode(node)) {
// function invocation: fn(2, 3) or obj.fn(2, 3) or (anything)?.(2, 3)
openParams(state)
getToken(state)

Expand All @@ -1453,7 +1433,7 @@ export const createParse = /* #__PURE__ */ factory(name, dependencies, ({
closeParams(state)
getToken(state)

node = new FunctionNode(node, params)
node = new FunctionNode(node, params, optional)
} else {
// implicit multiplication like (2+3)(4+5) or sqrt(2)(1+2)
// don't parse it here but let it be handled by parseImplicitMultiplication
Expand Down Expand Up @@ -1484,12 +1464,15 @@ export const createParse = /* #__PURE__ */ factory(name, dependencies, ({
node = new AccessorNode(node, new IndexNode(params), optional)
} else {
// dot notation like variable.prop
getToken(state)
// consume the `.` (if it was ?., already consumed):
if (!optional) getToken(state)

const isPropertyName = state.tokenType === TOKENTYPE.SYMBOL ||
(state.tokenType === TOKENTYPE.DELIMITER && state.token in NAMED_DELIMITERS)
if (!isPropertyName) {
throw createSyntaxError(state, 'Property name expected after dot')
let message = 'Property name expected after '
message += optional ? 'optional chain' : 'dot'
throw createSyntaxError(state, message)
}

params.push(new ConstantNode(state.token))
Expand Down
54 changes: 54 additions & 0 deletions test/unit-tests/expression/parse.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -956,6 +956,8 @@ describe('parse', function () {
const res = parseAndEval('obj["b"] = 2', scope)
assert.strictEqual(res, 2)
assert.deepStrictEqual(scope, { obj: { a: 3, b: 2 } })
assert.deepStrictEqual(
parseAndEval('b = {}; b.a = 2; b').valueOf(), [{ a: 2 }])
})

it('should set a nested object property', function () {
Expand All @@ -965,6 +967,17 @@ describe('parse', function () {
assert.deepStrictEqual(scope, { obj: { foo: { bar: 2 } } })
})

it(
'should not set an object property through optional chaining',
function () {
assert.throws(
() => parseAndEval('obj = {a: 2}; obj?.b = 7'), SyntaxError)
assert.throws(
() => parseAndEval('obj = {a: 2}; obj?.["b"] = 7'), SyntaxError)
assert.throws(
() => parseAndEval('obj = {a: {}}; obj.a?.b = 7'), SyntaxError)
})

it('should throw an error when trying to apply a matrix index as object property', function () {
const scope = { a: {} }
assert.throws(function () {
Expand Down Expand Up @@ -1196,6 +1209,13 @@ describe('parse', function () {
assert.throws(function () { parseAndEval('obj.foo["bar"].baz', { obj: { foo: { bar: null } } }) }, TypeError)
})

it('should throw an error when using double-dot after optional chaining operator', function () {
// ?.. is not valid in JavaScript and should be rejected
assert.throws(function () { parseAndEval('{a: 3}?..a') }, /SyntaxError: Property name expected after optional chain \(char 9\)/)
assert.throws(function () { parseAndEval('obj?..foo', { obj: { foo: 2 } }) }, /SyntaxError: Property name expected after optional chain \(char 6\)/)
assert.throws(function () { parseAndEval('obj?.["a"]?..b', { obj: { a: { b: 2 } } }) }, /SyntaxError: Property name expected after optional chain \(char 13\)/)
})

it('should set an object property with dot notation', function () {
const scope = { obj: {} }
parseAndEval('obj.foo = 2', scope)
Expand Down Expand Up @@ -1471,6 +1491,40 @@ describe('parse', function () {
parseAndEval('2(x, 2) = x^2', scope)
}, SyntaxError)
})

it('should call functions via optional chaining', function () {
assert.strictEqual(parseAndEval('square?.(2)'), 4)
assert.deepStrictEqual(parseAndEval('f(x) = x+x; f?.(2)').valueOf(), [4])
assert.strictEqual(parseAndEval('(_(x) = x^x)?.(2)'), 4)
assert.strictEqual(parseAndEval('foo?.(2)', { foo: x => x * x }), 4)
assert.deepStrictEqual(
parseAndEval('f(x) = 4x/x; bar = {a: f}; bar.a?.(2)').valueOf(), [4])
})

it(
'should shortcircuit undefined functions via optional chaining',
function () {
assert.strictEqual(
parseAndEval('foo?.(2)', { foo: undefined }), undefined)
assert.strictEqual(parseAndEval('{a: 3}.foo?.(2)'), undefined)
assert.strictEqual(
parseAndEval('foo.bar?.(2)', { foo: {} }), undefined)
assert.deepStrictEqual(
parseAndEval('f(x) = undefined; f(0)?.(2)').valueOf(), [undefined])
assert.strictEqual(parseAndEval('(undefined)?.(2)'), undefined)
assert.strictEqual(parseAndEval('foo?.(2)'), undefined)
})

it('should throw with optional chain call on non-function', function () {
// I guess it is OK to consider this a syntax error since we know just
// by reading the expression that the function call can't succeed.
assert.throws(() => parseAndEval('7?.(2)'), SyntaxError)
assert.throws(() => parseAndEval('a = 7; a?.(2)'), TypeError)
assert.throws(() => parseAndEval('(3+4)?.(2)'), TypeError)
assert.throws(() => parseAndEval('add(3,4)?.(2)'), TypeError)
assert.throws(() => parseAndEval('{a: true}.a?.(2)'), Error)
assert.throws(() => parseAndEval('[3, 4]?.(2)'), TypeError)
})
})

describe('parentheses', function () {
Expand Down