In practice the current implementation isn't actually using this, and if
we need access to states in future we can access them in either the
plan.PriorState or plan.PrevRunState fields, depending on which stage we
want a state snapshot of.
Previously we were repeating some logic in the UI layer in order to
recover relevant additional context about a change to report to a user.
In order to help keep things consistent, and to have a clearer path for
adding more such things in the future, here we capture this user-facing
idea of an "action reason" within the plan model, and then use that
directly in order to decide how to describe the change to the user.
For the moment the "tainted" situation is the only one that gets a special
message, matching what we had before, but we can expand on this in future
in order to give better feedback about the other replace situations too.
This also preemptively includes the "replacing by request" reason, which
is currently not reachable but will be used in the near future as part of
implementing the -replace=... plan command line option to allow forcing
a particular object to be replaced.
So far we don't have any special reasons for anything other than replacing,
which makes sense because replacing is the only one that is in a sense
a special case of another action (Update), but this could expand to
other kinds of reasons in the future, such as explaining which of the
few different reasons a data source read might be deferred until the
apply step.
The previous implementation of views was copying and embedding the base
View struct in each individual view. While this allowed for easy access
to the interface of that struct (both in the view and externally), it more
importantly completely broke the ability of the diagnostic printer to
output source code snippets.
This is because the `configSources` field on the base view is lazily set
after the config loader is initialized. In the commands ported to use
views, this happens after the base View struct is copied, so we are
updating the wrong copy of the struct.
This commit fixes this with a simple mechanical refactor: keep a pointer
to the base View struct instead, and update all of the individual views
to explicitly refer to that struct to access its fields and methods.
This is not a particularly satisfying solution, but I can't find
anything clearly better. It might be worth exploring the alternative
approach in the view for the new test command, which explicitly pulls
its dependencies out of the base view, rather than retaining a full
reference. Maybe there's a third way which is better still.
This commit extracts the remaining UI logic from the local backend,
and removes access to the direct CLI output. This is replaced with an
instance of a `views.Operation` interface, which codifies the current
requirements for the local backend to interact with the user.
The exception to this at present is interactivity: approving a plan
still depends on the `UIIn` field for the backend. This is out of scope
for this commit and can be revisited separately, at which time the
`UIOut` field can also be removed.
Changes in support of this:
- Some instances of direct error output have been replaced with
diagnostics, most notably in the emergency state backup handler. This
requires reformatting the error messages to allow the diagnostic
renderer to line-wrap them;
- The "in-automation" logic has moved out of the backend and into the
view implementation;
- The plan, apply, refresh, and import commands instantiate a view and
set it on the `backend.Operation` struct, as these are the only code
paths which call the `local.Operation()` method that requires it;
- The show command requires the plan rendering code which is now in the
views package, so there is a stub implementation of a `views.Show`
interface there.
Other refactoring work in support of migrating these commands to the
common views code structure will come in follow-up PRs, at which point
we will be able to remove the UI instances from the unit tests for those
commands.
Martin Atkins