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Preserve state reference if unchanged and not in transaction #25

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merged 4 commits into from
Mar 1, 2018
Merged

Preserve state reference if unchanged and not in transaction #25

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889294a
Preserve state reference if unchanged and not in transaction
aduth Feb 28, 2018
087cba9
Ensure original reducer called with inner state
aduth Feb 28, 2018
1682380
Add test to ensure optimist not in original reducer state
aduth Feb 28, 2018
46b6329
Avoid multiple calls to original reducer
aduth Mar 1, 2018
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11 changes: 9 additions & 2 deletions src/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -109,8 +109,15 @@ function optimist(fn) {
return revertReducer(state, action);
}
}
let separated = separateState(state);
return baseReducer(separated.optimist, separated.innerState, action);

let {optimist, innerState} = separateState(state);
if (state) {
let nextState = fn(innerState, action);
if (nextState === innerState && !optimist.length) {
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I think there are two new problems here:

  1. If optimist.length > 0 we should skip straight to baseReducer, not also run fn first.
  2. It looks like fn is potentially getting called twice here (if it applies a change). The fn should only ever be called once per action.

return state;
}
}
return baseReducer(optimist, innerState, action);
};
}

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19 changes: 19 additions & 0 deletions test/index.js
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Expand Up @@ -264,6 +264,17 @@ basic('commit other transaction', {
}
});

test('omits optimist from original reducer', () => {
function originalReducer(state = {value: 0}, action) {
assert(state.value === 0);
assert(!state.hasOwnProperty('optimist'));
return state;
}
let reducer = optimist(originalReducer);
let state;
state = reducer(state, {type: 'foo'});
state = reducer(state, {type: 'foo'});
});

test('real world example', () => {
function originalReducer(state = {value: 0}, action) {
Expand Down Expand Up @@ -387,6 +398,14 @@ test('real world example 2', () => {
assert.deepEqual(state, {optimist: [], value: 4});
});

test('unhandled action state reference', () => {
let originalReducer = ( state = {} ) => state;
let reducer = optimist(originalReducer);
let initState = reducer(undefined, {type: '@@init'});
let originalState = reducer(initState, {type: 'UNHANDLED_ACTION'});
let nextState = reducer(originalState, {type: 'UNHANDLED_ACTION'});
assert.strictEqual(originalState, nextState);
});

function basic(name, {reducer, before, action, after}) {
test(name, () => {
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