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@sdumetz
sdumetz committed Dec 4, 2023
1 parent ced1647 commit c2fec55
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83 changes: 68 additions & 15 deletions source/server/utils/merge.test.ts
View file
Original file line number Diff line number Diff line change
Expand Up @@ -117,29 +117,55 @@ describe("three-way merge", function(){
//The camera node's position can safely be ignored as it will get reset on load, in favor of `scene.setups[].navigation`
});

describe.skip("conflict resolution", function(){
describe("fields ignore optimization", function(){
//This is a potential optimization
//The camera node's position can safely be ignored as it will get reset on load, in favor of `scene.setups[].navigation`
it("ignores camera translation changes", function(){
const ref = {nodes:[{name:"camera", translation:[1,0,0]}]};
const next = {nodes:[{name:"camera", translation:[0,1,0]}]};
expect(apply(ref, diff(ref, next))).to.deep.equal({nodes:[{name:"camera", translation:[1,0,0]}]});
});
})

describe("conflict resolution", function(){
//Test only cases where "smart" conflict resolution is possible
describe("by ID", function(){
//Here it would be possible to differentiate annotations or articles by their id
//thus detecting a double-push and resolving it
const A1 = { "id": "mMzG2tLjmIst", "titles": { "EN": "A1"} }
const A2 = { "id": "FiIaONzRIbL4", "titles": { "EN": "A2"} }
const A3 = { "id": "rJpCltJjxyyL", "titles": { "EN": "A3"} }
let A1: any, A2: any, A3 : any;
beforeEach(function(){
A1 = { "id": "mMzG2tLjmIst", "titles": { "EN": "A1"} }
A2 = { "id": "FiIaONzRIbL4", "titles": { "EN": "A2"} }
A3 = { "id": "rJpCltJjxyyL", "titles": { "EN": "A3"} }
});

it("handle double array push (annotations)", function(){
const ref = {annotations: [A1], title: "foo"};
const current = {annotations: [A1,A2]};
const next = {annotations: [A1,A3]};
const ref = {annotations: [A1]};
const current = {annotations: [A1, A2]};
const next = {annotations: [A1, A3]};

const d = diff(ref, next);
expect(d).to.deep.equal({annotations: {1: A3}});
expect(apply(current, d)).to.deep.equal({annotations: [A1,A2,A3], title: "foo"});
expect(apply(current, d)).to.deep.equal({annotations: [A1, A2, A3]});
});

it("can still modify annotations in place", function(){
const A1b = {"id": "mMzG2tLjmIst", "titles": { "EN": "A1b", "FR": "A1b"} }
const ref = {annotations: [A1]};
const current = {annotations: [A1, A2]};
const next = {annotations: [A1b]};
expect(apply(current, diff(ref, next))).to.deep.equal({annotations: [A1b, A2]});

})

it.skip("handle double array push (articles)", function(){
const ref = {articles: [A1], title: "foo"};
const current = {articles: [A1,A2]};
const next = {articles: [A1,A3]};
expect(apply(current, diff(ref, next))).to.deep.equal({articles: [A1,A2,A3], title: "foo"});
it("handle double array push (articles)", function(){
const ref = {articles: [A1]};
const current = {articles: [A1, A2]};
const next = {articles: [A1, A3]};
const d = diff(ref, next);
expect(d).to.deep.equal({articles: {1: A3}});
const patch = apply(current, d)
expect(patch, JSON.stringify(patch)).to.deep.equal({articles: [A1, A2, A3]});
});
})

Expand All @@ -156,7 +182,6 @@ describe("three-way merge", function(){
const next = {nodes: [N1,N3], scenes:[{nodes:[0, 1]}]};

expect(apply(current, diff(ref, next))).to.deep.equal({nodes: [N1,N2,N3], scenes:[{nodes:[0, 1, 2]}]});
//FIXME a node's children might also be affected.
});

it("reassign nodes children appropriately", function(){
Expand All @@ -165,8 +190,36 @@ describe("three-way merge", function(){

["lights", "cameras", "models"].forEach(type=>{
it(`reassign ${type} appropriately`, function(){
//Lights have no property that could be used to differentiate them
const stype = type.slice(0, -1);
function make(nodes: object[]=[], types: object[]=[]){
return {
nodes: [
{name: `${stype}.0`, [stype]: 0},
...nodes,
], [type]:[
{reference: "default item"},
[...types]
]
};
}
//Lights, cameras and models have no property that could be used to differentiate them
//We can only suppose that if someone adds a node, the light attached to this node is unique to this one and should stay with it.
const ref = make();
const current = make([{name: `${stype}.current`, [stype]: 1}], [{reference: "current_item"}]);
const next = make([{name: `${stype}.next`, [stype]: 1}], [{reference: "next_item"}]);

expect(apply(current, diff(ref, next))).to.deep.equal({
nodes: [
{name: `${stype}.0`, [stype]: 0},
{name: `${stype}.current`, [stype]: 1},
{name: `${stype}.next`, [stype]: 2},
], [type]:[
{reference: "default item"},
{reference: "current_item"},
{reference: "next_item"},
]
});

});
});
});
Expand Down
107 changes: 88 additions & 19 deletions source/server/utils/merge.ts
View file
Original file line number Diff line number Diff line change
@@ -1,4 +1,14 @@

/**
* Special symbol to mark a field for deletion in a diff object
*/
export const DELETE_KEY = Symbol("_DELETE_KEY");

type Diff<T> = {
[K in keyof T]?: typeof DELETE_KEY|Diff<T[K]>|T[K]|Record<number, any>;
}


/**
* Deep assign two or more objects
* Like `Object.assign()` but recursive
Expand All @@ -10,26 +20,68 @@ export function apply<T extends Record<string, any>>(into :T, ...diffs :Diff<T>[
for(const diff of diffs){
for(const key in diff){
const value = diff[key] as T[Extract<keyof T, string>];
if(value === DELETE_KEY) delete into[key];
else if(typeof diff[key] == "object"){
if(typeof into[key] !== "object") into[key] = {} as any;
apply(into[key], value);
}else{
into[key] = value;
if(apply_core(into, key, value)){
continue;
}

//Then handle arrays to apply edge cases
if(Array.isArray(into[key])){
apply_array(into[key], value);
continue;
}
//Default case : recurse.
into[key] ??= {} as any;
apply(into[key], value);
}
}
return into;
}

//Handle special merge conditions for arrays
function apply_array<T extends Array<any>>(into :T, ...diffs :Diff<T>[]):T{
for (const diff of diffs){
for(const idx in diff){
const value = diff[idx];
if(apply_core(into, idx, value)){
continue;
}
if(typeof into[idx] !== undefined){
if(value.id){
const ref_id = into[idx].id;
if(ref_id && ref_id != value.id){
into.push(value);
continue;
}
}
/**
* @todo names should more or less follow the same rules but are trickier
* Because they require a parent lookup to also reorder affected nodes.
*/
}
//Default case : recurse as apply() would.
into[idx] ??= {} as any;
apply(into[idx], value);
}
}
return into;
}


export const DELETE_KEY = Symbol("MERGE_DELETE_KEY");
function apply_core<T extends Record<string, any>>(into :T, key:keyof T, value :any):boolean{

type Diff<T> = {
[K in keyof T]?: typeof DELETE_KEY|Diff<T[K]>|T[K]|Record<number, any>;
}
if(value === DELETE_KEY){
delete into[key];
return true;
}

if(typeof value !== "object"){
//Handle primitives
into[key] = value;
return true;
}

return false;
}

/**
* Computes a diff between two objects.
Expand All @@ -46,17 +98,34 @@ export function diff<T extends Record<string,any>>(from :T, to :T) :Diff<T>{
let r :Diff<T> = {} as any;
const keys :Set<keyof T>= new Set([...Object.keys(from), ...Object.keys(to)]);
for(const key of keys.values()){
if(typeof to[key] == "undefined") r[key] = DELETE_KEY;
else if(typeof from[key] == "object"){
if(to[key] == null){
if(from[key] != null ) r[key] = null as T[Extract<keyof T, string>];
}else{
const d = diff(from[key] as any, to[key] as any);
if(Object.keys(d).length) r[key] = d;
}
}else if(from[key] !== to[key]){

if(typeof to[key] == "undefined"){
r[key] = DELETE_KEY;
continue;
}

if(typeof from[key] != "object"){
if(from[key] === to[key]) continue;
//Simple case with primitive values
//console.log("Assigning ", key, to[key]);
r[key] = to[key];
continue;
}

//Handle cases where `typeof from[key] === "object"`
if(to[key] == null){
//Null is special because it can't be fed back to diff() recursively
if(from[key] != null ) r[key] = null as T[Extract<keyof T, string>];
continue;
}

const d = diff(from[key] as any, to[key] as any);
if(Object.keys(d).length){
//console.log("Diffing", key, from[key], to[key]);
r[key] = d;
}


}
return r;
}

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