Add tests for optional chaining

[DanielRosenwasser]

Filing an issue to add tests for https://github.com/tc39/proposal-optional-chaining/

Statement List

• UpdateExpression[Yield, Await]

  • • OptionalExpression[Yield, Await]
    • • MemberExpression[Yield, Await] (member-expression.js)
      • • PrimaryExpression[?Yield, ?Await]
        • • this
        • • IdentifierReference[?Yield, ?Await]
          • • Identifier
        • • Literal
        • • ArrayLiteral[?Yield, ?Await]
        • • ObjectLiteral[?Yield, ?Await]
        • • FunctionExpression
        • • ClassExpression[?Yield, ?Await]
        • • GeneratorExpression
        • • AsyncFunctionExpression
        • • AsyncGeneratorExpression
        • • RegularExpressionLiteral
        • • TemplateLiteral[?Yield, ?Await, ~Tagged]
        • • CoverParenthesizedExpressionAndArrowParameterList[?Yield, ?Await]
      • • MemberExpression[?Yield, ?Await][Expression[+In, ?Yield, ?Await]]
      • • MemberExpression[?Yield, ?Await].IdentifierName
      • • MemberExpression[?Yield, ?Await]TemplateLiteral[?Yield, ?Await, +Tagged]
      • • SuperProperty[?Yield, ?Await]
      • • MetaProperty
      • • newMemberExpression[?Yield, ?Await]Arguments[?Yield, ?Await]
    • • CallExpression[Yield, Await] (call-expression.js)
      • • CoverCallExpressionAndAsyncArrowHead[?Yield, ?Await]
      • • SuperCall[?Yield, ?Await]
      • • CallExpression[?Yield, ?Await]Arguments[?Yield, ?Await]
      • • CallExpression[?Yield, ?Await][Expression[+In, ?Yield, ?Await]]
      • • CallExpression[?Yield, ?Await].IdentifierName
      • • CallExpression[?Yield, ?Await]TemplateLiteral[?Yield, ?Await, +Tagged]
    • • OptionalExpression[Yield, Await]
      • • MemberExpression[?Yield, ?Await]OptionalChain[?Yield, ?Await]
      • • CallExpression[?Yield, ?Await]OptionalChain[?Yield, ?Await]
      • • OptionalExpression[?Yield, ?Await]OptionalChain[?Yield, ?Await]
  • • OptionalExpression[no LineTerminator here]++ (invalid) (update-expression.js)
  • • OptionalExpression[no LineTerminator here]-- (invalid) (update-expression.js)
  • • ++OptionalExpression[?Yield, ?Await] (invalid) (update-expression.js)
  • • --OptionalExpression[?Yield, ?]Await] (invalid) (update-expression.js)

• AssignmentExpression[In, Yield, Await] (assignment-expression.js)

  • • ConditionalExpression[?In, ?Yield, ?Await]
  • • ArrowFunction[?In, ?Yield, ?Await]
  • • AsyncArrowFunction[?In, ?Yield, ?Await]
  • • OptionalExpression[Yield?, Await?] = AssignmentExpression[?In, ?Yield, ?Await] (invalid)
  • • OptionalExpression AssignmentOperatorAssignmentExpression[?In, ?Yield, ?Await] (invalid)

• DestructuringAssignmentTarget[Yield, Await] (assignment-expression.js)

• • OptionalExpression[?Yield, ?Await]

• IterationStatement[Yield, Await, Return]: (iteration-statement.js)

  • • doStatement[?Yield, ?Await, ?Return] while(Expression[+In, ?Yield, ?Await]);
  • • while(Expression[+In, ?Yield, ?Await]) Statement[?Yield, ?Await, ?Return]
  • • for([lookahead ∉ { let [ }]Expression[~In, ?Yield, ?Await]opt;Expression[+In, ?Yield, ?Await]opt;Expression[+In, ?Yield, ?Await]opt)Statement[?Yield, ?Await, ?Return]
  • • for(varVariableDeclarationList[~In, ?Yield, ?Await];Expression[+In, ?Yield, ?Await]opt;Expression[+In, ?Yield, ?Await]opt)Statement[?Yield, ?Await, ?Return]
  • • for(LexicalDeclaration[~In, ?Yield, ?Await]Expression[+In, ?Yield, ?Await]opt;Expression[+In, ?Yield, ?Await]opt)Statement[?Yield, ?Await, ?Return]
  • • for([lookahead ∉ { let [ }]LeftHandSideExpression[?Yield, ?Await]inExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • for(varForBinding[?Yield, ?Await]inExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • for(ForDeclaration[?Yield, ?Await]inExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • for([lookahead ≠ let]LeftHandSideExpression[?Yield, ?Await]ofAssignmentExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • for(varForBinding[?Yield, ?Await]ofAssignmentExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • for(ForDeclaration[?Yield, ?Await]ofAssignmentExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]

• ClassHeritage[Yield, Await]: (class-heritage.js)

  • • extends OptionalExpression[?Yield, ?Await]

Async Function

• UpdateExpression[Yield, Await]

  • • OptionalExpression[Yield, Await]
    • • MemberExpression[Yield, Await] (async-member-expression.js)
      • • PrimaryExpression[?Yield, ?Await]
        • • this
        • • IdentifierReference[?Yield, ?Await]
          • • Identifier
          • • await Identifier
        • • Literal
        • • ArrayLiteral[?Yield, ?Await]
        • • ObjectLiteral[?Yield, ?Await]
        • • FunctionExpression
        • • ClassExpression[?Yield, ?Await]
        • • GeneratorExpression
        • • AsyncFunctionExpression
        • • AsyncGeneratorExpression
        • • RegularExpressionLiteral
        • • TemplateLiteral[?Yield, ?Await, ~Tagged]
        • • CoverParenthesizedExpressionAndArrowParameterList[?Yield, ?Await]
      • • MemberExpression[?Yield, ?Await][Expression[+In, ?Yield, ?Await]]
      • • MemberExpression[?Yield, ?Await].IdentifierName
      • • MemberExpression[?Yield, ?Await]TemplateLiteral[?Yield, ?Await, +Tagged]
      • • SuperProperty[?Yield, ?Await]
      • • MetaProperty
      • • newMemberExpression[?Yield, ?Await]Arguments[?Yield, ?Await]
    • • CallExpression[Yield, Await] (async-call-expression.js)
      • • CoverCallExpressionAndAsyncArrowHead[?Yield, ?Await]
      • • SuperCall[?Yield, ?Await]
      • • CallExpression[?Yield, ?Await]Arguments[?Yield, ?Await]
      • • CallExpression[?Yield, ?Await][Expression[+In, ?Yield, ?Await]]
      • • CallExpression[?Yield, ?Await].IdentifierName
      • • CallExpression[?Yield, ?Await]TemplateLiteral[?Yield, ?Await, +Tagged]
    • • OptionalExpression[Yield, Await]
      • • MemberExpression[?Yield, ?Await]OptionalChain[?Yield, ?Await]
      • • CallExpression[?Yield, ?Await]OptionalChain[?Yield, ?Await]
      • • OptionalExpression[?Yield, ?Await]OptionalChain[?Yield, ?Await]
  • • OptionalExpression[no LineTerminator here]++ (invalid) (async-update-expression.js)
  • • OptionalExpression[no LineTerminator here]-- (invalid) (async-update-expression.js)
  • • ++OptionalExpression[?Yield, ?Await] (invalid) (async-update-expression.js)
  • • --OptionalExpression[?Yield, ?]Await] (invalid) (async-update-expression.js)

• AssignmentExpression[In, Yield, Await] (async-assignment-expression.js)

  • • ConditionalExpression[?In, ?Yield, ?Await]
  • • ArrowFunction[?In, ?Yield, ?Await]
  • • AsyncArrowFunction[?In, ?Yield, ?Await]
  • • OptionalExpression[Yield?, Await?] = AssignmentExpression[?In, ?Yield, ?Await] (invalid)
  • • OptionalExpression AssignmentOperatorAssignmentExpression[?In, ?Yield, ?Await] (invalid)

• DestructuringAssignmentTarget[Yield, Await] (async-assignment-expression.js)

• • OptionalExpression[?Yield, ?Await]

• IterationStatement[Yield, Await, Return]: (async-iteration-statement.js)

  • • doStatement[?Yield, ?Await, ?Return] while(Expression[+In, ?Yield, ?Await]);
  • • while(Expression[+In, ?Yield, ?Await]) Statement[?Yield, ?Await, ?Return]
  • • for([lookahead ∉ { let [ }]Expression[~In, ?Yield, ?Await]opt;Expression[+In, ?Yield, ?Await]opt;Expression[+In, ?Yield, ?Await]opt)Statement[?Yield, ?Await, ?Return]
  • • for(varVariableDeclarationList[~In, ?Yield, ?Await];Expression[+In, ?Yield, ?Await]opt;Expression[+In, ?Yield, ?Await]opt)Statement[?Yield, ?Await, ?Return]
  • • for(LexicalDeclaration[~In, ?Yield, ?Await]Expression[+In, ?Yield, ?Await]opt;Expression[+In, ?Yield, ?Await]opt)Statement[?Yield, ?Await, ?Return]
  • • for([lookahead ∉ { let [ }]LeftHandSideExpression[?Yield, ?Await]inExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • for(varForBinding[?Yield, ?Await]inExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • for(ForDeclaration[?Yield, ?Await]inExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • for([lookahead ≠ let]LeftHandSideExpression[?Yield, ?Await]ofAssignmentExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • for(varForBinding[?Yield, ?Await]ofAssignmentExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • for(ForDeclaration[?Yield, ?Await]ofAssignmentExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • [+Await]forawait([lookahead ≠ let]LeftHandSideExpression[?Yield, ?Await]ofAssignmentExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • [+Await]forawait(varForBinding[?Yield, ?Await]ofAssignmentExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]
  • • [+Await]forawait(ForDeclaration[?Yield, ?Await]ofAssignmentExpression[+In, ?Yield, ?Await])Statement[?Yield, ?Await, ?Return]

Iterator Function

• UpdateExpression[Yield, Await]

  • • OptionalExpression[Yield, Await]
    • • MemberExpression[Yield, Await] (iterator-member-expression.js)
      • • PrimaryExpression[?Yield, ?Await]
        • • this
        • • IdentifierReference[?Yield, ?Await]
          • • yield Identifier

• AssignmentExpression[In, Yield, Await] (iterator-assignment-expression.js)

  • • [+Yield]YieldExpression[?In, ?Await]

[leobalter]

We already have an initial PR:

#2212

[leobalter]

I updated the OT with the checklist contents produced by @bcoe.

[bcoe]

@leobalter @DanielRosenwasser if we're happy with this check list as a start, I'll put some open source time in this weekend and work my way through a bunch of the cases; I love this sort of work.

[DanielRosenwasser]

Only if you don't view it as an inconvenience - otherwise, I think it'd be awesome if you're up for it 😄

Leo will know more about the contribution process - ways that make it more approachable etc.

[leobalter]

This checklist is pretty comprehensive and I believe it's a great start. We can add interesting edgy cases along the way as we identify them.

BTW: one edgy case that I discussed with my team this week, based on #2262:

var stored = [];
var x = {
  set y(v) { stored.push(`set y with ${v}`); }
  get y() { stored.push('get y'); }
};
// dstr assignment
[ x?.y = 1 ] = [ 42 ];
assert.sameValue(stored.length, 1);
assert.sameValue(stored[0], 42);

[ljharb]

Im confused; why would optional chaining be permitted in a destructuring context?

[leobalter]

Checkout the ref issue. It’s valid to have a LHSExpr inside an ArrayAssignment literal. Which I believe makes it consistent to have opt chaining there.

…

On Wed, Jul 31, 2019 at 8:29 PM Jordan Harband ***@***.***> wrote: Im confused; why would optional chaining be permitted in a destructuring context? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#2263?email_source=notifications&email_token=AACJREKG6LCBGF3WKDSNP53QCIU5DA5CNFSM4IH7GK2KYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD3I6EZI#issuecomment-517071461>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AACJREMVFNJM5QEEX4HHMC3QCIU5DANCNFSM4IH7GK2A> .

[leobalter]

Well, https://tc39.es/proposal-optional-chaining/#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget

There is an explicit exception for this grammar, so [x.y = 1] = [42] remains valid while [x?.y = 1] = [42] is a parse error. We still need test for that, this is a documented and expected error.

[bcoe]

it would be good to add tests for the edge-cases demonstrated here:

v8/v8@ceb7bd5#diff-9b0c860cbf7e0482f43ad30124ee9f9bR92

Mainly:

• super?.foo calls.
• new?.bar calls.

[bcoe]

CC: @devsnek 👋 saw you've already done some initial implementation work in V8, awesome 😄

we're gradually fleshing out a thorough set of tests here which you can run against, let me know if you bump into any issues.

[bcoe]

Just a quick update, I have started work on the async tests for optional chaining (have just been fairly busy with a few other tasks).

[bcoe]

@DanielRosenwasser @leobalter @rkirsling, it feels like we could still improve coverage for Stage 4 in December. I saw the rollback of #2411, where should we ultimately end up in terms of generated tests vs., hand written tests, is it worth continuing to work down the check-lists we've written up ... alternatively, perhaps we're feeling that we've covered a healthy number of productions?

[leobalter]

@bcoe would you be able (time-wise) to update the coverage list or flag parts missing in the coverage?

We can make a work effort after that or as you said, define coverage is reasonable enough. WDYT?

[bcoe]

@leobalter I'll make an effort to put some work into it this weekend, at least summarizing some of the productions we didn't quite hit yet.

I definitely do think we're getting to the point where we have a healthy number of tests, but I think there are some areas we could flesh out more (as an example for and while statements).

[bcoe]

@leobalter @jridgewell @DanielRosenwasser, I'm feeling pretty good about our initial suite of tests (once we land #2429 which addresses some regressions @jridgewell brought up).