René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"intent to implement - rework of stack trace decoration","articleBody":"This is an attempt to finally fix the inconsistent stack decoration in node core... hopefully future-facing enough for everyone.\r\n\r\nthe final code might not be js but the logic will look something like this:\r\n\r\n```js\r\n  // Called for every stack trace in the isolate.\r\n  // more consistency as a platform and no more\r\n  // calling decorateErrorStack which\r\n  // is super slow and inconsistent.\r\n  // Using the V8 callback also means we don't need\r\n  // to store the state of whether an exception has\r\n  // been decorated, V8 does it for us.\r\n  setPrepareStackTraceCallback(\r\n    (global, shouldNotDecorate, safeToString, error, frames, message) =\u003e {\r\n\r\n      // V8 engine prepareStackTrace polyfill\r\n      // To be buffer-constructor-style-deprecated\r\n      // if/when ECMA262 error stacks API is finalized.\r\n      // Being able to explicitly bail here means we don't\r\n      // run into double-decoration issues, like with my last\r\n      // attempt to fix stack decoration.\r\n      if (global.Error !== undefined \u0026\u0026\r\n          typeof global.Error.prepareStackTrace === 'function') {\r\n        return global.Error.prepareStackTrace(error, frames);\r\n      }\r\n\r\n      const errorString = safeToString(error);\r\n\r\n      // checks for Symbol.for('node.error.decorate') === false\r\n      // or an internal weakset for core things (iirc there were one\r\n      // or two places where we disable the arrow so i threw this in)\r\n      if (shouldNotDecorate(error)) {\r\n        return `${errorString}\\n    at ${frames.join('\\n    at ')}`;\r\n      }\r\n\r\n      const [\r\n        sourceLine,\r\n        resourceName,\r\n        lineNumber,\r\n        startColumn,\r\n        endColumn,\r\n      ] = message;\r\n\r\n      // same output we have now\r\n      return `${resourceName}:${lineNumber}\r\n${sourceLine}\r\n${' '.repeat(startColumn)}${'^'.repeat(endColumn - startColumn)}\r\n${errorString}\r\n    at ${frames.join('\\n    at ')}`;\r\n});\r\n```\r\n\r\ni have a patch here (https://chromium-review.googlesource.com/c/v8/v8/+/1119768) to implement the API callback in V8 (and after that lands I have another patch lined up to make v8::StackTrace movable to js-land) but before any of that happens V8 wants to know we will actually use this.\r\n\r\nThe only thing not handled here is when node has an uncaught non-error exception: https://github.com/nodejs/node/blob/811598bcdae74ed8460ccb265d9939f36858f75a/src/node.cc#L976-L985 but i think we can still make that work if we really want to (i would argue that we shouldn't)\r\n\r\n/cc @hashseed @schuay @addaleax @Trott","author":{"url":"https://github.com/devsnek","@type":"Person","name":"devsnek"},"datePublished":"2018-07-24T14:13:45.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":21},"url":"https://github.com/21958/node/issues/21958"}