Pat Gavlin e1a52693dc Add support for importing existing resources. (#2893) ... A resource can be imported by setting the `import` property in the resource options bag when instantiating a resource. In order to successfully import a resource, its desired configuration (i.e. its inputs) must not differ from its actual configuration (i.e. its state) as calculated by the resource's provider. There are a few interesting state transitions hiding here when importing a resource: 1. No prior resource exists in the checkpoint file. In this case, the resource is simply imported. 2. An external resource exists in the checkpoint file. In this case, the resource is imported and the old external state is discarded. 3. A non-external resource exists in the checkpoint file and its ID is different from the ID to import. In this case, the new resource is imported and the old resource is deleted. 4. A non-external resource exists in the checkpoint file, but the ID is the same as the ID to import. In this case, the import ID is ignored and the resource is treated as it would be in all cases except for changes that would replace the resource. In that case, the step generator issues an error that indicates that the import ID should be removed: were we to move forward with the replace, the new state of the stack would fall under case (3), which is almost certainly not what the user intends. Fixes #1662.		2019-07-12 11:12:01 -07:00
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index.ts	Add support for importing existing resources. (#2893)	2019-07-12 11:12:01 -07:00