update acorn@^7.3.1 for optional chaining support

[tanhauhau]

• Fixes '?' navigation operator #1972
• Fixes Compiler error when referencing import.meta.url in svelte scripts #4379

TODO:

• update upstreams for optional chaining
  • update code-red support optional chaining Rich-Harris/code-red#45 (merged, but pending new version from code-red)
  • update @types/estree for estree type definition [estree] optional chain, nullish coallesce DefinitelyTyped/DefinitelyTyped#45470 (apparently, this is not a dependency of svelte 🤔 )
• Add test
• support optional chaining in binding bind:value={a?.b} ?

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• This message body should clearly illustrate what problems it solves. If there are related issues, remember to reference them.
• Ideally, include a test that fails without this PR but passes with it. PRs will only be merged once they pass CI. (Remember to npm run lint!)

Tests

• Run the tests tests with npm test or yarn test)

[tanhauhau]

not sure why in is-reference https://github.com/Rich-Harris/is-reference/blob/ca593f330bff5660efec747ddc5973e875e2f923/module.js#L2-L4, MemberExpression is treated as reference for certain scenario, which may lead to lost of optional chaining, because of some code generation logic in Svelte

svelte/src/compiler/compile/render_dom/Renderer.ts

Line 298 in 38de3b2

return nodes.reduce((lhs, rhs) => x`${lhs}.${rhs}`);

[Conduitry]

I've just published [email protected].

[Conduitry]

It looks like there's still a TS build error here.

I'm not sure what I think about bind:value={a?.b}. What would that do if a were nullish? Nothing? Set it to { b }? Maybe for now it should be a compilation error?

[tanhauhau]

the TS error was due to 2 @types/estree instance, as is-reference and code-red installed 2 different absolute version of @types/estree.

created a PR for that Rich-Harris/is-reference#9

Maybe for now it should be a compilation error?

okay, it is a compilation error for now, since currently only MemberExpression and Identifier is supported, and optional chain is a ChainExpression .

[qm3ster]

Does this branch in the current state enable compiling ?. and ??? Because I tried to git depend on it and it didn't for me.
Not rushing anyone, just assumed it would from the checkmarks in the description and the fact this is marked as closing #1972.
This includes adding lang="typescript". Does it need a specific typescript config?

[Conduitry]

@tanhauhau It took a little npm wrangling to get it to update just the relevant bits, but here's the diff I have right now for the lockfile:

diff --git a/package-lock.json b/package-lock.json
index 1bb4bbfff..25b0b6703 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -167,9 +167,9 @@
       "dev": true
     },
     "@types/estree": {
-      "version": "0.0.39",
-      "resolved": "https://registry.npmjs.org/@types/estree/-/estree-0.0.39.tgz",
-      "integrity": "sha512-EYNwp3bU+98cpU4lAWYYL7Zz+2gryWH1qbdDTidVd6hkiR6weksdbMadyXKXNPEkQFhXM+hVO9ZygomHXp+AIw==",
+      "version": "0.0.45",
+      "resolved": "https://registry.npmjs.org/@types/estree/-/estree-0.0.45.tgz",
+      "integrity": "sha512-jnqIUKDUqJbDIUxm0Uj7bnlMnRm1T/eZ9N+AVMqhPgzrba2GhGG5o/jCTwmdPK709nEZsGoMzXEDUjcXHa3W0g==",
       "dev": true
     },
     "@types/is-windows": {
@@ -2250,12 +2250,12 @@
       "dev": true
     },
     "is-reference": {
-      "version": "1.1.4",
-      "resolved": "https://registry.npmjs.org/is-reference/-/is-reference-1.1.4.tgz",
-      "integrity": "sha512-uJA/CDPO3Tao3GTrxYn6AwkM4nUPJiGGYu5+cB8qbC7WGFlrKZbiRo7SFKxUAEpFUfiHofWCXBUNhvYJMh+6zw==",
+      "version": "1.2.1",
+      "resolved": "https://registry.npmjs.org/is-reference/-/is-reference-1.2.1.tgz",
+      "integrity": "sha512-U82MsXXiFIrjCK4otLT+o2NA2Cd2g5MLoOVXUZjIOhLurrRxpEXzI8O0KZHr3IjLvlAH1kTPYSuqer5T9ZVBKQ==",
       "dev": true,
       "requires": {
-        "@types/estree": "0.0.39"
+        "@types/estree": "*"
       }
     },
     "is-regex": {

I'm still seeing type errors when building though - three messages about src/compiler/compile/nodes/shared/Context.ts.

[Conduitry]

With the above lockfile changes, and forcing Context.ts to compile despite the remaining type errors, this does seem to be working. However, the REPL itself won't work yet, because the version of Rollup used there (1.27.0) does not support these syntax features. So the compiler produces the correct output but then the bundler chokes on it. I've opened sveltejs/svelte-repl#122 which would be nice to get to in the immediate future but I don't think it should block this PR.

[tanhauhau]

I've applied your package-lock.json diff, and fixed the type errors!