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Block Editor: Avoid block removal when calling 'moveBlockToPosition' #75728

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Merged
Mamaduka merged 1 commit into from
Feb 20, 2026
Merged

Block Editor: Avoid block removal when calling 'moveBlockToPosition' #75728

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3 changes: 3 additions & 0 deletions packages/block-editor/src/store/reducer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1083,6 +1083,9 @@ export const blocks = pipe(
if ( fromRootClientId === toRootClientId ) {
const subState = state.get( toRootClientId );
const fromIndex = subState.indexOf( clientIds[ 0 ] );
if ( fromIndex === -1 ) {

@ntsekouras ntsekouras Feb 20, 2026

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Should we be selectively defensive against wrong API usage? I mean, it's fine to add this but there are so many more paths that things can break with wrong usage.

@Mamaduka Mamaduka Feb 20, 2026

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What do you have in mind? There are many ways similar actions can be misused; I think guarding against content loss is a good start.

IMO, the fromRootClientId argument isn't really required here; we can derive that value from clientIds, but now that would be hard to migrate without breaking something.

We could silently patch the wrong fromRootClientId, but consumers might still use the action incorrectly without even knowing it.

@ntsekouras ntsekouras Feb 20, 2026

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I told you I'm fine with this small change, but I find it weird to be defensive like that and I'll share my thinking.

If I was the one that tried to use that (or any other API) and noticed the issue. I'd see the docs/code and just call the API with the proper argument, that I had missed.. Or I'd suggest in an issue to have a you're doing it wrong message etc..

We could silently patch the wrong fromRootClientId, but consumers might still use the action incorrectly without even knowing it.

That's still the case now.. They don't really know it's wrong, and even though they don't have content loss, they still don't know it's a no-op.

Anyway, that was a harmless change and shared my thoughts candidly. No reason to spent more time on this philosophical discussion I think 😄

@Mamaduka Mamaduka Feb 20, 2026

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Thanks for great feedback, Nik!

return state;
}
const newState = new Map( state );
newState.set(
toRootClientId,
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37 changes: 37 additions & 0 deletions packages/block-editor/src/store/test/reducer.js
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Expand Up @@ -1841,6 +1841,43 @@ describe( 'state', () => {
] );
} );

it( 'should not remove last block when fromRootClientId is incorrect', () => {
const original = blocks( undefined, {
type: 'RESET_BLOCKS',
blocks: [
{
clientId: 'chicken',
name: 'core/test-block',
attributes: {},
innerBlocks: [],
},
{
clientId: 'ribs',
name: 'core/test-block',
attributes: {},
innerBlocks: [
{
clientId: 'nested',
name: 'core/test-block',
attributes: {},
innerBlocks: [],
},
],
},
],
} );
const state = blocks( original, {
type: 'MOVE_BLOCKS_TO_POSITION',
clientIds: [ 'nested' ],
fromRootClientId: '',
toRootClientId: '',
index: 0,
} );

// The state should be unchnaged - no blocks moved or removed.
expect( state.order.get( '' ) ).toEqual( [ 'chicken', 'ribs' ] );
} );

describe( 'blocks', () => {
describe( 'byClientId', () => {
it( 'should ignore updates to non-existent block', () => {
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