feat: support using and await using
#1369
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acorn/src/statement.js
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| decl.id = this.parseBindingAtom() | ||
| this.checkLValPattern(decl.id, kind === "var" ? BIND_VAR : BIND_LEXICAL, false) | ||
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| if (kind === "using" || kind === "await using") { | ||
| if (decl.id.type === "ObjectPattern") { | ||
| this.raise(decl.id.start, "Using declaration cannot have destructuring patterns") | ||
| } | ||
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| if (decl.id.type === "ArrayPattern") { | ||
| for (let elem of decl.id.elements) { | ||
| if (elem && elem.type === "RestElement") { | ||
| this.raise(elem.start, "Unexpected token '...'") | ||
| } | ||
| } | ||
| } | ||
| } |
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Thank you for working on this PR!
I know you're still working in progress, but let me comment.
I think this method handles LexicalBinding.
Following the spec, I thought it would be more direct to write it like this, but what do you think?
decl.id = kind === "using" || kind === "await using"
? this.parseIdent()
: this.parseBindingAtom()
this.checkLValPattern(decl.id, kind === "var" ? BIND_VAR : BIND_LEXICAL, false)There was a problem hiding this comment.
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| pp.parseForAfterInit = function(node, init, awaitAt) { | ||
| if ((this.type === tt._in || (this.options.ecmaVersion >= 6 && this.isContextual("of"))) && init.declarations.length === 1) { | ||
| if (this.options.ecmaVersion >= 9) { | ||
| if (this.type === tt._in) { | ||
| if (awaitAt > -1) this.unexpected(awaitAt) | ||
| } else node.await = awaitAt > -1 | ||
| } | ||
| return this.parseForIn(node, init) | ||
| } | ||
| if (awaitAt > -1) this.unexpected(awaitAt) | ||
| return this.parseFor(node, init) | ||
| } |
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I moved this from line number 226 ~ 235.
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@baseballyama Thank you for making progress on this PR!
I'm not familiar with the specs so I may be wrong, but let me comment to the best of my understanding.
| // --- ECMAScript version compatibility --- | ||
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| // ES16: using should be treated as regular identifier (assignment) | ||
| test("using = 5;", { |
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I think it would be good to have a test for this in ES17.
Also, I think it would be good to have some of the following tests in ES17.
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added: 7babfd3
acorn/src/statement.js
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| return isIdentifierStart(ch, true) || ch === 92 // '\' | ||
| } | ||
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| pp.isAwaitUsingDeclaration = function() { |
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The naming seemed inconsistent to me.
The next method name is isUsing, so I think isAwaitUsing would be better here.
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updated: 17b3f85
| }, {"ecmaVersion": 17}); | ||
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| // Top-level using declaration | ||
| test("using x = resource;", { |
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From what I understand, this is an early error, because I don't think we can have a top-level using declaration for a script. However, I think it is allowed for modules.
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fixed: 5f1f124
test/tests-using.js
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| }] | ||
| }], | ||
| sourceType: "script" | ||
| }, {"ecmaVersion": 17}); |
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Could you please add the following test?
As I understand it can be parsed, but it is not an unsing declaration.
for (using of x) {}There was a problem hiding this comment.
fixed: c395a8b
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@ota-meshi Thank you very much for your review!!! It was really helpful! |
acorn/src/statement.js
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| this.raise(this.start, "Using declaration cannot appear in the top level when source type is `script`") | ||
| } | ||
| this.next() | ||
| if (usingKind === "await using") this.next() |
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I would think that {await using a = x} in sourceType: script would be a syntax error, but it doesn't seem to be the case currently. I think maybe we should check this.canAwait here.
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Thank you! fixed: e59ede7
FEATURE: Support `using` and `await using` syntax. Issue #1369
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Thanks for your work on this @baseballyama! And for the reviews, @ota-meshi. I have no further issues with this. Merged as b4ae0d2. I'll cut a release in a few days if no further issues come up. |
close: #1366