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Rework hooks structure to be a linkedlist 

Allows for safe removal of hooks whilst they are being invoked
This commit is contained in:
Nick O'Leary 2021-04-26 21:14:42 +01:00
parent 250005ad16
commit f7210effec
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GPG Key ID: 4F2157149161A6C9
2 changed files with 100 additions and 26 deletions
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87
packages/node_modules/@node-red/util/lib/hooks.js vendored
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@ -20,7 +20,16 @@ const VALID_HOOKS = [
// Flags for what hooks have handlers registered
let states = { }
// Hooks by id
// Doubly-LinkedList of hooks by id.
// - hooks[id] points to head of list
// - each list item looks like:
// {
// cb: the callback function
// location: filename/line of code that added the hook
// previousHook: reference to previous hook in list
// nextHook: reference to next hook in list
// removed: a flag that is set if the item was removed
// }
let hooks = { }
// Hooks by label
@ -54,20 +63,33 @@ function add(hookId, callback) {
if (VALID_HOOKS.indexOf(id) === -1) {
throw new Error(`Invalid hook '${id}'`);
}
if (label) {
if (labelledHooks[label] && labelledHooks[label][id]) {
throw new Error("Hook "+hookId+" already registered")
}
labelledHooks[label] = labelledHooks[label]||{};
labelledHooks[label][id] = callback;
if (label && labelledHooks[label] && labelledHooks[label][id]) {
throw new Error("Hook "+hookId+" already registered")
}
// Get location of calling code
const stack = new Error().stack;
const callModule = stack.split("\n")[2].split("(")[1].slice(0,-1);
Log.debug(`Adding hook '${hookId}' from ${callModule}`);
hooks[id] = hooks[id] || [];
hooks[id].push({cb:callback,location:callModule});
const hookItem = {cb:callback, location: callModule, previousHook: null, nextHook: null }
let tailItem = hooks[id];
if (tailItem === undefined) {
hooks[id] = hookItem;
} else {
while(tailItem.nextHook !== null) {
tailItem = tailItem.nextHook
}
tailItem.nextHook = hookItem;
hookItem.previousHook = tailItem;
}
if (label) {
labelledHooks[label] = labelledHooks[label]||{};
labelledHooks[label][id] = hookItem;
}
// TODO: get rid of this;
states[id] = true;
}
@ -100,21 +122,29 @@ function remove(hookId) {
}
}
function removeHook(id,callback) {
let i = hooks[id].findIndex(hook => hook.cb === callback);
if (i !== -1) {
hooks[id].splice(i,1);
if (hooks[id].length === 0) {
delete hooks[id];
delete states[id];
}
function removeHook(id,hookItem) {
let previousHook = hookItem.previousHook;
let nextHook = hookItem.nextHook;
if (previousHook) {
previousHook.nextHook = nextHook;
} else {
hooks[id] = nextHook;
}
if (nextHook) {
nextHook.previousHook = previousHook;
}
hookItem.removed = true;
if (!previousHook && !nextHook) {
delete hooks[id];
delete states[id];
}
}
function trigger(hookId, payload, done) {
const hookStack = hooks[hookId];
if (!hookStack || hookStack.length === 0) {
let hookItem = hooks[hookId];
if (!hookItem) {
if (done) {
done();
return;
@ -124,7 +154,7 @@ function trigger(hookId, payload, done) {
}
if (!done) {
return new Promise((resolve,reject) => {
invokeStack(hookStack,payload,function(err) {
invokeStack(hookItem,payload,function(err) {
if (err !== undefined && err !== false) {
if (!(err instanceof Error)) {
err = new Error(err);
@ -137,18 +167,21 @@ function trigger(hookId, payload, done) {
})
});
} else {
invokeStack(hookStack,payload,done)
invokeStack(hookItem,payload,done)
}
}
function invokeStack(hookStack,payload,done) {
let i = 0;
function invokeStack(hookItem,payload,done) {
function callNextHook(err) {
if (i === hookStack.length || err) {
if (!hookItem || err) {
done(err);
return;
}
const hook = hookStack[i++];
const callback = hook.cb;
if (hookItem.removed) {
hookItem = hookItem.nextHook;
callNextHook();
return;
}
const callback = hookItem.cb;
if (callback.length === 1) {
try {
let result = callback(payload);
@ -161,6 +194,7 @@ function invokeStack(hookStack,payload,done) {
result.then(handleResolve, callNextHook)
return;
}
hookItem = hookItem.nextHook;
callNextHook();
} catch(err) {
done(err);
@ -177,6 +211,7 @@ function invokeStack(hookStack,payload,done) {
}
function handleResolve(result) {
if (result === undefined) {
hookItem = hookItem.nextHook;
callNextHook();
} else {
done(result);

39
test/unit/@node-red/util/lib/hooks_spec.js
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@ -121,7 +121,46 @@ describe("util/hooks", function() {
})
})
})
it("allows a hook to remove itself whilst being called", function(done) {
let data = { order: [] }
hooks.add("onSend.A", function(payload) { payload.order.push("A") } )
hooks.add("onSend.B", function(payload) {
hooks.remove("*.B");
})
hooks.add("onSend.C", function(payload) { payload.order.push("C") } )
hooks.add("onSend.D", function(payload) { payload.order.push("D") } )
hooks.trigger("onSend", data, err => {
try {
should.not.exist(err);
data.order.should.eql(["A","C","D"])
done();
} catch(e) {
done(e);
}
})
});
it("allows a hook to remove itself and others whilst being called", function(done) {
let data = { order: [] }
hooks.add("onSend.A", function(payload) { payload.order.push("A") } )
hooks.add("onSend.B", function(payload) {
hooks.remove("*.B");
hooks.remove("*.C");
})
hooks.add("onSend.C", function(payload) { payload.order.push("C") } )
hooks.add("onSend.D", function(payload) { payload.order.push("D") } )
hooks.trigger("onSend", data, err => {
try {
should.not.exist(err);
data.order.should.eql(["A","D"])
done();
} catch(e) {
done(e);
}
})
});
it("halts execution on return false", function(done) {
hooks.add("onSend.A", function(payload) { payload.order.push("A"); return false } )