1652079 - mutationBreakpoint type is incorrectly written with an "s" in the IMMEDIATE_MUTATIONS array

Status: RESOLVED FIXED

(DevTools :: Inspector, defect, P3)

Description

[Julian Descottes [:jdescottes]]

When implementing mutation breakpoints as new custom mutations to the inspector, a small mistake was made:

• the type is referred to as "mutationBreakpoints" (plural) in the IMMEDIATE_MUTATIONS array: https://searchfox.org/mozilla-central/rev/622dbd3409610ad3f71b56c9a6a92da905dab0aa/devtools/server/actors/inspector/walker.js#213
• the mutations are emitted as "mutationBreakpoint" (singular): https://searchfox.org/mozilla-central/rev/622dbd3409610ad3f71b56c9a6a92da905dab0aa/devtools/server/actors/inspector/walker.js#2142-2147

This means that mutationBreakpoints are currently queued and accumulated before they are sent to the client. In general adding new custom mutations should be avoided, and if the intent was to add them to IMMEDIATE_MUTATIONS, an event might be a better fit.

In this particular case, we need to decide if we simply remove the erroneous "mutationBreakpoints" from IMMEDIATE_MUTATIONS, or if we correct it. If we decide to correct it, we might as well switch to an event? The ultimate decision should depend on how frequent these events/mutations can be.

Comment 1

[Julian Descottes [:jdescottes]]

Hi Logan!

According to the comment in IMMEDIATE_MUTATIONS, it seems that we care about avoiding the queue for mutation breakpoint updates:

  // These should be delivered right away in order to be sure that the
  // fronts have not been removed due to other non-throttled mutations.
  "mutationBreakpoints",

But in practice, the feature has been working without being "immediate" (see summary above). Do you think we should remove the entry from the array, or should we fix it? And if we fix it, what about using a regular event instead of a mutation?

Comment 2

[Logan Smyth [:loganfsmyth]]

Hmmm, I guess we're okay to remove and we can see what happens.

Comment 3

[Julian Descottes [:jdescottes]]

Attachment: Bug 1652079 - Remove mutationBreakpoints from WalkerActor IMMEDIATE_MUTATIONS list

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/b97c31c96524
Remove mutationBreakpoints from WalkerActor IMMEDIATE_MUTATIONS list r=loganfsmyth

Comment 5

[Dorel Luca [:dluca]]

https://hg.mozilla.org/mozilla-central/rev/b97c31c96524