terraform/internal/initwd/testdata/load-module-package-escape/child/package-escape-child.tf

module "grandchild" {
  # NOTE: This seems like it ought to work because there is indeed a
  # ../grandchild directory, but our caller loaded us as an external
  # module using an absolute path and so we're actually isolated from
  # the parent directory in a separate "module package", and so we
  # can't traverse out to find the grandchild module.
  source = "../grandchild"
}
initwd: Error message for local paths escaping module packages Our module installer has a somewhat-informal idea of a "module package", which is some external thing we can go fetch in order to add one or more modules to the current configuration. Our documentation doesn't talk much about it because most users seem to have found the distinction between external and local modules pretty intuitive without us throwing a lot of funny terminology at them, but there are some situations where the distinction between a module and a module package are material to the end-user. One such situation is when using an absolute rather than relative filesystem path: we treat that as an external package in order to make the resulting working directory theoretically "portable" (although users can do various other things to defeat that), and so Terraform will copy the directory into .terraform/modules in the same way as it would download and extract a remote archive package or clone a git repository. A consequence of this, though, is that any relative paths called from inside a module loaded from an absolute path will fail if they try to traverse upward into the parent directory, because at runtime we're actually running from a copy of the directory that's been taking out of its original context. A similar sort of situation can occur in a truly remote module package if the author accidentally writes a "../" source path that traverses up out of the package root, and so this commit introduces a special error message for both situations that tries to be a bit clearer about there being a package boundary and use that to explain why installation failed. We would ideally have made escaping local references like that illegal in the first place, but sadly we did not and so when we rebuilt the module installer for Terraform v0.12 we ended up keeping the previous behavior of just trying it and letting it succeed if there happened to somehow be a matching directory at the given path, in order to remain compatible with situations that had worked by coincidence rather than intention. For that same reason, I've implemented this as a replacement error message we will return only if local module installation was going to fail anyway, and thus it only modifies the error message for some existing error situations rather than introducing new error situations. This also includes some light updates to the documentation to say a little more about how Terraform treats absolute paths, though aiming not to get too much into the weeds about module packages since it's something that most users can get away with never knowing. 2021-05-22 00:28:20 +02:00			`module "grandchild" {`
			`# NOTE: This seems like it ought to work because there is indeed a`
			`# ../grandchild directory, but our caller loaded us as an external`
			`# module using an absolute path and so we're actually isolated from`
			`# the parent directory in a separate "module package", and so we`
			`# can't traverse out to find the grandchild module.`
			`source = "../grandchild"`
			`}`