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F query panel inf loop

Summary

Focus

  • the browser's internal autocompletion was switched off with a one-liner.
  • The infinite loop happened when:
    1. Two consecutive calls to the reducer function with "onChange" on state s0. This sets the state.unresolvedSuggestions property (which is a promise) and results in two states, s1 and s2. s2 is now the current state and s1 is an old state which should just be forgotten.
    2. The useEffect hook triggers two times (once for each state.unresolvedSuggestions). This calls the reducer via the dispatch function.
    3. When the second unresolvedSuggestions promise resolves before the first, the reducer receives the old state s1, sets the state.suggestions and, originally, it copied the old (s1's) unresolvedSuggestions property which is different from s2's unresolvedSuggestions and henve triggers useEffect` a third time.
    4. Then the first unresolvedSuggestions promise resolves and sets the state back to s2, triggering useEffect a 4th time.
    5. The state then always switches between s1 and s2 and we have an infinite loop, voilá.
  • Because the timing is crucial here it is easier to provoke the loop when the computer is weak or under high load already. The browser's autocompletion popping up also made it more likely to trigger it.

Test Environment

  • New tests have been written, however it would make sense to try and provoke the loop manually by starting linkahead with the old implementation and this fix to see the actual impact of this fix.

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Edited by Florian Spreckelsen

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