Immutability check fails in development mode

[victorlin]

Current Behavior

Toggling streamtrees on → off → on causes the dev-only immutability middleware check to fail, resulting in an uncaught exception:

redux-toolkit.esm.js:467 Uncaught Error: Invariant failed: A state mutation was detected between dispatches, in the path 'tree.streams.2013 – West Africa.renderingOrder'.  This may cause incorrect behavior. (https://redux.js.org/style-guide/style-guide#do-not-mutate-state)
    at invariant (redux-toolkit.esm.js:467:9)
    at eval (redux-toolkit.esm.js:610:11)
    at Object.measureTime (redux-toolkit.esm.js:367:16)
    at eval (redux-toolkit.esm.js:606:22)
    at eval (redux-toolkit.esm.js:354:16)
    at dispatch (redux.js:627:28)
    at eval (treeStreams.ts:42:5)

at:

auspice/src/actions/treeStreams.ts

Line 42 in e6bb917

dispatch({type: TOGGLE_STREAM_TREE, showStreamTrees})

Redux doc: Do Not Mutate State

Expected behavior

No error.

Possible solution

I believe this is because TreeState.streams is mutated in processStreams, here and further down:

auspice/src/util/treeStreams.ts

Line 111 in e6bb917

streams[sigma] = (pivots.at(-1)-pivots.at(0))/nPivots*5;

[victorlin]

Also happens when streamtrees is on and attempting to toggle between time/divergence.

[jameshadfield]

#1979 originally had commits which would close this but I dropped them before merge:

I've dropped 3205d37 and the related fixup commit 94d3f3f which together would close #1982. We should aim for immutable state generally, although there's a lot of our tree-related state which is mutable and I don't think it's practical to make it immutable. I think streams can be made immutable but I wanted to hold off for 2 reasons:

1. Auspice has a history of nasty rendering bugs when we dispatch multiple times in quick succession. I think redux has made some progress here, and I know we can batch updates, but in general I find it easier to group together actions where feasible.
2. I'd like to look into the performance hit of structuredClone a little more (cf. just transferring references).

Let's revisit them in a new PR!

[jameshadfield]

P.S. the above linked commits used [window.]structuredClone. Polyfills for this are added as part of #1992, although I'm not sure we need to use it or whether we can use shallow clones etc.