support rotating by path

[nyobe]

Re-add support for specifying a subset of paths to rotate to #432.

Closes https://github.com/pulumi/pulumi-service/issues/25443

[pgavlin]

would love to see some more complex paths here--e.g. with quoted["property \"accessors\""], indices into lists, and normal dotted property access

[nyobe]

I've added more complex paths, and combined with parsing property paths it works well, thank you.

However, I tried to include one that is embedded within another function, but it seems like the expr paths in the evaluator are getting reset when parsing function arguments. should that be expected to work? (eg the expr's path when evaluating the examples.embedded-in-another-fn["fn::open::test"].some-input is just some-input)

[pgavlin]

Hmmm interesting. That's worth some more digging.

So there are two sorts of paths at play here: value paths and document paths. The former are the paths used in ${symbols.and.interpolations} and are resolved with respect to the schema of the fully-evaluated environment. The latter are resolved with respect to the YAML document. We want these paths to be document paths. I'm not sure what sort the paths on the expr nodes are (or what they're intended to be).

[nyobe]

okay, I'm not 100% sure, but I think that maybe expr.path is might be intended to be value path, based on the comment that it's for reporting cyclic reference errors. The path is built up by declare, which does reset the path when recursing into fn arguments.. (I think this might not be quite right even for value paths, since they should still be qualified by the parent path, but just eliding the function name, right?)

Anyway, it looks like I might be able to recover the document path from the ast node, using x.repr.syntax().Syntax().Syntax().Path() (which resolves to expr -> exprRepr -> ast.Expr -> syntax.Node -> syntax.Syntax (encoding.YAMLSyntax))`, so I'll switch to this instead.

[pgavlin]

One note about a surprising test case, LGTM otherwise