Previously we were using the experimental HCL 2 repository, but now we'll
shift over to the v2 import path within the main HCL repository as part of
actually releasing HCL 2.0 as stable.
This is a mechanical search/replace to the new import paths. It also
switches to the v2.0.0 release of HCL, which includes some new code that
Terraform didn't previously have but should not change any behavior that
matters for Terraform's purposes.
For the moment the experimental HCL2 repository is still an indirect
dependency via terraform-config-inspect, so it remains in our go.sum and
vendor directories for the moment. Because terraform-config-inspect uses
a much smaller subset of the HCL2 functionality, this does still manage
to prune the vendor directory a little. A subsequent release of
terraform-config-inspect should allow us to completely remove that old
repository in a future commit.
Because we gather together diagnostics from many different parts of the
codebase, the list often ends up being in a non-ideal order. Here we
define a partial ordering for diagnostics that should hopefully make them
easier to scan when many are present, by grouping together diagnostics
that are of the same severity and belong to the same file.
We use sort.Stable here because we have a partial order and so we need
to make sure that diagnostics that do not have a relative ordering will
remain in their original order.
This sorting is applied just in time before rendering the diagnostics
in command.Meta.showDiagnostics.
This is a variant of diagnosticsAsError that we use to signal to informed
callers that there might just be warnings inside, but we should also do
the right thing if a caller just appends it to an existing diagnostics
without checking first.
There is some existing practice in the "terraform" package of returning
a special error type ValidationError from EvalNode implementations in
order to return warnings without halting the graph walk even though a
non-nil error was returned.
This is a diagnostics-flavored version of that approach, allowing us to
avoid totally reworking the EvalNode concept around diagnostics and
retaining the ability to return non-fatal errors.
NonFatalErr is equivalent to the former terraform.ValidationError, while
ErrWithWarnings is a helper that automatically treats any errors as
fatal but returns NonFatalError if the diagnostics contains only warnings.
Previously we were showing only the summaries when converting to a string
error, but HCL generates summaries that indicate only the _type_ of error,
expecting that the detail will give the details, and so we need to show
both in order to produce a useful error message.
Due to the use of interfaces, Diagnostics is not super-friendly to the gob
encoding we currently use for plugin RPC. To mitigate this, we provide
a helper that converts all of the wrapped objects into a predictable flat
structure that we can pre-emptively register with gob.
This means that the decoded Diagnostics still has the same meaning as
the original, though the original wrapped errors (if any) are lost and
thus our errwrap integration won't be effective any longer.
Currently we lean heavily on the Go error type as our primary means of
describing errors, and along with that use several more specialized
implementations of it in different spots for additional capabilities such
as multiple errors in one object, source code range references, etc.
We also have a rather ad-hoc approach of returning an array of warnings
from certain functions along with one or multiple errors.
This rather-disorganized approach makes it hard for us to present
user-facing error messages consistently. As a step towards mitigating
this, package tfdiags provides a model for user-facing error and warning
messages and helper functions for creating them from various other
error and warning types used elsewhere in Terraform.
This mechanism is intended to be used to report errors and warnings where
the audience is the Terraform user, and so it may go a few layers deep
down the call stack into codepaths like config parsing, interpolation, etc
but is primarily a UX concern. The deepest reaches of Terraform core will
continue using "error" as normal, with higher layers preparing error
messages for presentation to the user.
To avoid needing to change the interface of every function that might
generate error diagnostics, the Diagnostics type can be "smuggled" via
an error value through other APIs and then unwrapped at the other end,
though it will lose any naked warnings (without at least one error) along
the way, and so codepaths that are expected to generate warnings
(validation, primarily) should use the concrete Diagnostics type
throughout the call chain.
Martin Atkins