René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[compiler] `IfExpression`s generating undefined instead of null","articleBody":"## Problem\r\n`lightscript@0.5.9`:\r\n```js\r\nx = if a:\r\n  if b: c\r\n```\r\n```js\r\nconst x = a ? b ? c : void 0 : null;\r\n```\r\nIf `a` is false, `x === null`, but if `a` is true and `b` is false, `x === undefined`; this is inconsistent with the defined behavior of `IfExpression`s which is to produce `null` when the alternate is omitted.\r\n\r\n## Cause\r\nThis:\r\nhttps://github.com/lightscript/babel-plugin-lightscript/blob/eb650acf69a17f0e4af9ce10a4c1bdeacec1e9e7/src/index.js#L504\r\nwhich leads to this:\r\nhttps://github.com/babel/babel/blob/1e55653ac173c3a59f403a7b5269cf6d143d32d9/packages/babel-traverse/src/path/replacement.js#L195\r\nwhich leads to this:\r\nhttps://github.com/babel/babel/blob/master/packages/babel-types/src/converters.js#L47\r\n\r\nBabel's algorithm for converting statements to expressions produces `undefined` by default.\r\n\r\n## Resolution\r\nIt is probably necessary to recapitulate this algorithm inside the lsc transform and make sure it makes `null`s here.","author":{"url":"https://github.com/wcjohnson","@type":"Person","name":"wcjohnson"},"datePublished":"2017-06-26T17:13:54.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/40/lightscript/issues/40"}