[IMP] web: Improve mockRead performance

This commit improves the performances of the mock server "read" handler
by reducing the amount of iterations performed on the current set of
records.

This was needed as some tests (namely: gantt manual performance tests)
mocked huge amounts of records and the main bottleneck was the mock
server, while the actual impact was supposed to be measured on the
rendering process.

Part-of: odoo/odoo#110819
Co-authored-by: Julien Mougenot <jum@odoo.com>
Co-authored-by: Mathieu Duckerts-Antoine <dam@odoo.com>

addons/web/static/tests/helpers/mock_server.js

@@ -882,28 +882,50 @@ export class MockServer {
             fields = Object.keys(model.fields);
         }
         const ids = Array.isArray(args[0]) ? args[0] : [args[0]];
-        const records = ids.reduce((records, id) => {
+        const records = [];
+
+        // Mapping of model records used in the current mockRead call.
+        const modelMap = {
+            [modelName]: {},
+        };
+        for (const record of model.records) {
+            modelMap[modelName][record.id] = record;
+        }
+        for (const fieldName of fields) {
+            const field = model.fields[fieldName];
+            if (!field) {
+                continue; // the field doesn't exist on the model, so skip it
+            }
+            const { relation, type } = field;
+            if (type === "many2one" && !modelMap[relation]) {
+                modelMap[relation] = {};
+                for (const record of this.models[relation].records) {
+                    modelMap[relation][record.id] = record;
+                }
+            }
+        }
+
+        for (const id of ids) {
             if (!id) {
                 throw new Error(
                     "mock read: falsy value given as id, would result in an access error in actual server !"
                 );
             }
-            const record = model.records.find((r) => r.id === id);
-            return record ? records.concat(record) : records;
-        }, []);
-        return records.map((record) => {
+            const record = modelMap[modelName][id];
+            if (!record) {
+                continue;
+            }
             const result = { id: record.id };
             for (const fieldName of fields) {
                 const field = model.fields[fieldName];
                 if (!field) {
-                    continue; // the field doens't exist on the model, so skip it
+                    continue; // the field doesn't exist on the model, so skip it
                 }
                 if (["float", "integer", "monetary"].includes(field.type)) {
                     // read should return 0 for unset numeric fields
                     result[fieldName] = record[fieldName] || 0;
                 } else if (field.type === "many2one") {
-                    const CoModel = this.models[field.relation];
-                    const relRecord = CoModel.records.find((r) => r.id === record[fieldName]);
+                    const relRecord = modelMap[field.relation][record[fieldName]];
                     if (relRecord) {
                         result[fieldName] = [record[fieldName], relRecord.display_name];
                     } else {
@@ -915,8 +937,10 @@ export class MockServer {
                     result[fieldName] = record[fieldName] || false;
                 }
             }
-            return result;
-        });
+            records.push(result);
+        }
+
+        return records;
     }
 
     mockReadGroup(modelName, kwargs) {