Using the generic unexpected token message in this case isn’t as helpful as it could be, because eof is a special sentinel token. For example:

42, // I am a comment.

The error is highlighted at the end of the comment rather than at the comma.

Right now we encourage usage of async generators, but browser support is limited. We should make it clear to readers that their browser doesn't support a feature, so that there isn't confusion about the notebook being potentially 'broken', etc.

currently, there are valid javascript expressions that use observables keywords mutable and viewof as identifiers that the observable parser will reject. the goal would be to allow these expressions where possible.

here are some examples of these identifiers that could be defined in a local cell scope:

{
  const viewof = 3;
}

function foo(viewof) { ... }

and at the notebook scope where cells can be named mutable and viewof:

function viewof() { ... }

viewof = 3

additionally, import semantics need to be worked out. what happens if a cell named viewof is imported from another notebook that defines it as a cell:

import { viewof } from "..."

this change is likely to alter logic in parse.js, and the Hello, Observable Parser notebook can be used to aid in testing.

broadly this change would be a preamble to possibly adding a builtin keyword to provide a namespace for all the built-in identifiers like width.

jsdelivr doesn't know how to use this package because there's no "main" specified in package.json, so a parser = require('@observablehq/praser') in observable will fail.

more info in this notebook

It’d be nice if there were a way to opt-in to getting a promise of a cell’s next value. This would allow two things:

1. A cell could start running before a cell it references has fulfilled. This would allow some operations to proceed in parallel, without needing to break these operations out into another cell.

2. A cell could handle an error if a cell it references errors. For example, promiseof foo.catch(() => "default") or try { return await promiseof foo; } catch { return "default"; }. Related observablehq/runtime#286.

For development, I've found the following to be extremely useful:

#!/usr/bin/env node -r esm

import {parseCell} from "./src/index";
import {readFileSync} from "fs";

const actual = parseCell(readFileSync(process.argv[2], "utf8"), {
  globals: null
});

actual.fileReferences = Array.from(actual.fileReferences.entries());
console.log(JSON.stringify(actual, null, 2));

So that I can write compact test files and re-run them without test noise. I think we should add something similar to the repo to assist in development for people with similar preferences.

We already ignore them in modules, so we might as well ignore them in cells.

The dependency acorn-walk was updated from 6.1.1 to 6.2.0.

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Do we have plan for TypeScript support or even consider it?
Not sure if this is the right place to ask questions like this though, my apologies!

The devDependency eslint was updated from 6.0.1 to 6.1.0.

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This is currently acorn-observable, but should probably be @observablehq/acorn-observable.

https://twitter.com/atomless/status/1128969450357690368
https://observablehq.com/@atomless/default-values-in-object-destructured-function-args

Same kind of issue as bigints and async generators: Shipping Chrome (2 versions ago) includes new syntax:

class Example {
  classFields = 0;
  #privateField = 0;
  static #field = 4;
  static method() { };
}

This should possibly start from this class fields plugin.

Describe the bug

Demo: https://observablehq.com/d/1fb03f01444425d2

Given a cell foo with

foo = "bar"

when defining a cell where the value is referenced as a destructuring default for an instance property:

function Test1(opts = {}) {
  ({a: this.a = foo} = opts);
}  

Observable will erroneously report

SyntaxError: Assignment to constant variable foo

To avoid the error, the cell value has to be assigned to an intermediate variable.

For example, the following pattern works:

function Test2(opts = {}) {
  const _foo = foo;
  ({a: this.a = _foo} = opts);
}  

as does:

function Test3(opts = {}, bar = foo) {
  ({a: this.a = bar} = opts);
}  

Moved from https://github.com/observablehq/notebook/issues/597 because this is where the errors live. We can, and I think should, make errors around common JS that doesn't run in Observable clearer, and I think some of the common cases can be solved cleanly.

The dependency acorn was updated from 6.2.0 to 6.2.1.

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Raised by @mbostock - as soon as we start wrapping setTimeout, setInterval, and other time-control functions, we should warn against using their non-wrapped versions. ( that issue: https://github.com/observablehq/notebook/issues/861 )

These should be warnings - styled differently than errors, and potentially with auto-fix options.

See for example https://observablehq.com/@airbornemint/units

I would like to import it using

import { m } with { "," as thousands_separator } from "@airbornemint/units"

But that gives me a parse error and I have to use two cells, one to define new_thousands_separator = "," and the other to import { m } with { new_thousands_separator as thousands_separator } from "@airbornemint/units", which seems unnecessarily verbose for what is basically a module-level configuration parameter specified at the time of import.

acornjs/acorn#835

Acorn is doing BigInt parsing without a plugin, and we should take advantage of that once they ship their next release.

Use case: Display an inline code block containing the literal text <div ...${props} /> using a Markdown cell

Expected behavior: escape the ${} with a \: <div ...\${props} /> or <div ...$\{props} /> or <div ...\$\{props} />

Actual results:

• <div ...\${props} /> tries to evaluate props
• <div ...$\{props} /> outputs <div ...$\{props} />
• <div ...\$\{props} /> outputs <div ...\$\{props} />

The devDependency rollup-plugin-commonjs was updated from 10.0.1 to 10.0.2.

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import('hello');

Should work, but is currently a syntax error.

Would it be possible to remove the line + column from the error message, this information is included in the thrown error, so users can format the message as they wish?

Reproduction: https://observablehq.com/d/ac1f28041d650918

foo = ({[field]: value}) => value

field = "bar"

foo({bar: 42})

Expected behavior: the last cell evaluates to 42.
Observed behavior: the last throws ReferenceError: field is not defined

Sometimes this module yields an id node that's derived from a function or class name, and other times it returns an id from id = at the beginning of the node. For clarity, for printing its AST and choosing when to prepend id =, we should indicate in the AST which is which.

The devDependency rollup was updated from 1.14.2 to 1.14.3.

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The devDependency husky was updated from 3.0.2 to 3.0.3.

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