mirror of https://github.com/pulumi/pulumi.git
6b4805672c
When using `--target` to target specific resources during an update, we
use the list of targets to decide which steps to generate given a set of
resource registrations. Specifically:
* If the registration event names a resource that is targeted, we
process it as usual.
* If the registration event names a resource that _is not_ targeted, we
emit a `SameStep` for it.
In the latter case, the emission of a `SameStep` means that the old
state for the resource will be copied across to the new state. This is
the desired behaviour -- the resource was not targeted and so the new
state should contain the resource exactly as it was prior to the update.
However, this presents a problem if the old state has references to
resources that either will not appear in the new state, or will appear
in the wrong place. Consider the following program in TypeScript-esque
pseudocode:
```typescript
const a = new Resource("a")
const b = new Resource("b", { dependency: a })
const c = new Resource("c")
```
Here, `b` depends on `a`, while `a` and `c` have no dependencies. We run
this program without specifying targets and obtain a state containing
`a`, `b` and `c`, with `a` appearing before `b` due to `b`'s dependency
on `a`. We now modify the program as follows:
```typescript
const b = new Resource("b")
const c = new Resource("c")
```
`a` has been removed from the program and consequently `b` no longer
depends on it. We once more run the program, this time with a `--target`
of `c`. That is to say, neither `a` nor `b` is targeted. The execution
proceeds as follows:
* `a` is not in the program, so no `RegisterResourceEvent` will be
emitted and processed for it.
* `b` is in the program, but it is not targeted. Its
`RegisterResourceEvent` will be turned into a `SameStep` and `b`'s _old
state will be copied as-is to the new state_.
* `c` is in the program and is targeted. It will be processed as normal.
At the end of execution when we come to write the snapshot, we take the
following actions:
* We first write the processed resources: `b`'s old state and `c`'s new
state.
* We then copy over any unprocessed resources from the base (previous)
snapshot. This includes `a` (which is again desirable since its deletion
should not be processed due to it not being targeted).
Our snapshot is now not topologically sorted and thus invalid: `b` has a
dependency on `a`, but `a` appears after it. Presently this bug will
manifest irrespective of the nature of the dependency: `.Dependencies`,
`.PropertyDependencies` and `.DeletedWith` are all affected.
This commit fixes this issue by traversing all untargeted resource
dependency relationships and ensuring that `SameStep`s (or better if
they have been targeted) are emitted before emitting the depending
resource's `SameStep`.
* Fixes #16052
* Fixes #15959
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