Original PR: https://github.com/babel/babel/pull/2469. Seems this got
lost in the v6 changes.
- - -
Without this, the only way to replace the arrow function is to either
manually override its `node.body`, or duplicate the arrow:
```js
// Old
ArrowFunctionExpression: function (node) {
node.body = t.blockStatement(...);
// Or
return t.ArrowFunctionExpression(
node.params,
t.blockStatement(...),
node.async
);
}
// New
ArrowFunctionExpression: function() {
this.get("body").replaceWith(t.blockStatement(...));
}
```
Given the following `.babelrc`:
```
{
"plugins": ["./myPluginDir/somePlugin.js"]
}
```
Babel should resolve that plugin relative to the directory that contains the `.babelrc` file.
Currently, Babel is resolving the plugin relative to the current `process.cwd()`, as you can see in this test case: https://github.com/skevy/babel-plugin-resolution-test-case
This is occurring because the "fake" `Module` that we're creating in the `resolve` helper doesn't have an `id` and `filename`. Therefore, Node builds an array of paths that contains a number of node_module paths as well as `.`, and doesn't contain the path in which we'd actually like to look up the plugin. `.` of course resolves to the current `process.cwd()`, and thus makes the Babel plugin resolution mechanism quite fragile. The relevant code in Node.JS can be found here (tagged at the v5.4.1 release): ff99203724/lib/module.js (L236-L242).
This PR adds `id` and `filename` to that fake `Module` in order to resolve this issue.
This introduces "pass per preset" feature, spawting a new traversal for each preset in case if the `passPerPreset` is `true` (default is `false`). This gives opportunity to define "before" and "after" presets, mimicking a similar feature from Babel 5. A rationally for this is to make plugins as short as possible, and handled only needed nodes, not afrading potential collisions in case if presets are merged.
Rather than repeating the original location when we exit a node, we need to restore the previous parent’s original line location, since the source map format denotes the start location.
As a follow up from #3145 we agreed to add a new format that is a
superset of the compact format option. Do things that are considered
dangerous. e.g. not printing semicolons, or print literal values
as opposed to raw values.
