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A change that touches only a stack's outputs is not shown in v1

Decision record 0036

Records 0007 and 0021 left one question open: how to show a change that touches a stack’s outputs and no resource. In v1 it is not shown. A stack whose preview holds no resource change and no tracking change is in sync, whatever happened to its outputs.

The reason is what the tool gives us. A test with a file backend (Pulumi CLI 3.198.0, one resource, then one output added) gave this from pulumi preview --json: changeSummary was { "same": 2 }, the root stack step was same, and its newState had no outputs at all. The document that record 0001 builds on cannot tell that an output changed. The human text does say + added, and so does the event stream behind PULUMI_ENABLE_STREAMING_JSON_PREVIEW, where the last outputs event of the root stack lists the new output names.

Moving the adapter to the event stream for this was rejected for v1. It is a second parser with its own recorded fixtures, for a case that is rare on its own: an output nearly always changes together with the resource it comes from, and then the row is pending anyway. Comparing output values was rejected outright. Many outputs are unknown until the deploy runs, and the values of outputs are as sensitive as any other value (0021).

Consequences

  • The cost is real and the docs say it: a stack whose only change is an added, removed or changed output has no checkbox, so it cannot be deployed from the dashboard. Another stack that reads the new output through a stack reference keeps failing its preview until someone deploys the first stack from outside Sluiceway, which is legal (0016).
  • The Pulumi adapter drops the root stack step when it is same, as the research said. The build records a fixture for this case with the minimum CLI version (0001), so a CLI that starts to report output changes is noticed.
  • The door stays open without a breaking change. An output change would arrive as one change per stack: op is update, the address names the stack’s outputs, type reads outputs, and changedKeys holds the output names. Names only, never values (0021). It is an update even when an output is removed, because no real object goes away, so it can never raise a destroy warning (0007). It joins the hash by the rule of 0008. Rows of stacks with such a change get a new hash once.
  • OpenTofu reports output changes in output_changes, so its adapter can use the same shape from its first day.