internal/core/eval: handle embedded top correctly

Other basic types were already correctly handled,
but top slipped through the maze.

Uncovered while debugging Issue cuelang#758

Change-Id: Iee99e0a0c5e8c1a7b2faa02b484c64f0e549391f
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/8707
Reviewed-by: CUE cueckoo <[email protected]>
Reviewed-by: Paul Jolly <[email protected]>

internal/core/adt: "fix" disjunction resolution

The recent performance improvement eliminated disjuncts
too aggressively, causing some disjuncts to disappear.
Early elimination prevents exponential blowup, but of course
it should not make it incorrect.

Note that for most common uses, like protobuf and K8s
structs with discriminator fields, special optimizations exist
that make this linear. But this has not been implemented yet.

Now this fix exposed another bug. This bug was deliberate to
work around a limitation of default values when representing
oneOf fields. We planned to introduce a "required field" annotation
which would also allow to represent these kind of semantics
much more elegantly.

For now, though, we are stuck in a position that more than one
oneOf field cannot be represented properly with defaults.
We fix it for now in an even more AWFUL way, and instead work
towards a proper solution based on required fields.

Issue cuelang#726

Change-Id: Id4bcd0445612e12fba48a744654de4e1852c552e
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/8641
Reviewed-by: Paul Jolly <[email protected]>
Reviewed-by: Marcel van Lohuizen <[email protected]>

internal/core/adt: fix performance issue with disjunctions

Fixes a performance TODO, which was a deliberate regression
to deal with a semantic bug.

Fixes cuelang#651

Change-Id: I9d95dc9d250064e79552425331912f58175cc094
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/8282
Reviewed-by: Marcel van Lohuizen <[email protected]>

internal/core/adt: fix regression in close builtin

Would in some cases recursively close.

Now uses just one method for marking closedness. Marking
Closed in the Vertex was only used so that the debug printer
would show the closed status. This has now fixed. This was
not possible before but is now as the code was recently
simplified.

Fixes cuelang#642

Change-Id: I9aab6a02f36ddbc8ed9bce356a2f4ad77cd30cda
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/8228
Reviewed-by: CUE cueckoo <[email protected]>
Reviewed-by: Marcel van Lohuizen <[email protected]>

internal/core/adt: catch errors for circular failures

This mechansim can ultimately also be used for
communicating any change that makes a Vertex
more specific.

Change-Id: Ia5d86fd4cc7da53290998aa5e08de12a474ec440
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/8113
Reviewed-by: CUE cueckoo <[email protected]>
Reviewed-by: Marcel van Lohuizen <[email protected]>

internal/core/eval: keep semantics for [K]: T

We were contemplating to redefine [string]: T to
be JSON Schema semantics. For this purpose, tool
fix rewrote it into a form that means the same in
both interpretations.

In the end, the original CUE semantics seem useful
enough to keep with the benefit of not breaking
people. We now anticipate to add the JSON semantics
using the notation: `[...K]: V`. With this approach, any
additional fields are always indicated with `...`.

Change-Id: I09dd4cd0bedc87917a29edba959e30a7b22cac5e
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/7906
Reviewed-by: Marcel van Lohuizen <[email protected]>
Reviewed-by: CUE cueckoo <[email protected]>

internal/core/export: dedup let clauses for merged structs

Let deduping already existed, but it could miss cases where
an identical let was added to the same scope, but originating
from different conjuncts, where the let originated from the
same struct.

Fixes cuelang#593

Change-Id: I47c806096ba885421005dfb297ae700c1c734040
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/7723
Reviewed-by: Marcel van Lohuizen <[email protected]>
Reviewed-by: CUE cueckoo <[email protected]>

cue/parser: support string selector labels

Allowed by the spec, but previously unimplemented.

Change-Id: I2fb7aad303cdfac8862a0744b80d524cb749f5b3
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/7342
Reviewed-by: Marcel van Lohuizen <[email protected]>
Reviewed-by: CUE cueckoo <[email protected]>

internal/core/adt: exclude definitions in data conversion

Definitions incorrectly trigger closedness for sub structures.
They also don't belong in data.

IMPORTANT: this implies that it is no longer possible to
refer to definitions from within tool files. As a workaround
we will allow it still for single-instance commands.

Fixes cuelang#525

Change-Id: I481dd16e7cacb1096f68d446ce1c5349b5cd4531
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/7143
Reviewed-by: CUE cueckoo <[email protected]>
Reviewed-by: Paul Jolly <[email protected]>

cue/load: relax places where @tag is allowed

Currently @tag can already be arbitrarily nested.
This now also allows embeddings. It now explicitly
disallows fields defined within lists or the scope of
an optional field in the help. It also reports an error
for invalid tag attributes.

These restrictions avoid an injection from being spread
to widely by being generated, which may increase the
ability to analyze a configuration. But if these restrictions
prove to be too cumbersome, they could be removed.

Closes cuelang#437

Change-Id: I3af3a49adb20e67fcce7c6693d40bfd14aa8eb0b
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/7082
Reviewed-by: Marcel van Lohuizen <[email protected]>