首先，populate不可能实现你想要做的事情。这是因为schema声明中的ref属性是用来引用一个模型，而不是一个路径。它用来告诉mongoose你想使用哪个模型来执行$lookup，mongoose希望那个模型对应于你数据库中的一个集合。
其次，您在productSchema中为featureHeaders和features数组使用子文档，因此无论如何populate都不适用。
幸运的是，你可以修复这个问题，让populate为你工作。虽然你的命名约定和用例有点混乱，希望这将有助于解释它是如何做到的：

1. FeatureHeader和Feature需要有它们自己的集合，而不是子文档，所以你需要为它们创建模型。

import mongoose from "mongoose";
const featureHeaderSchema = new mongoose.Schema({
    header: {
        type: String,
        required: true,
    }
});
// You need create the FeatureHeader model
const FeatureHeader = mongoose.model("FeatureHeader", featureHeaderSchema);

const featureSchema = new mongoose.Schema({
    title: {
        type: String,
        required: true,
    },
    parentHeader: { 
       type: mongoose.Schema.Types.ObjectId, 
       ref: "FeatureHeader" //< Reference the FeatureHeader model
    }, 
    parentFeature: { 
       type: mongoose.Schema.Types.ObjectId, 
       ref: "Feature" //< You can reference the same model (i.e self)
    }
});
// You need create the Feature model
const Feature = mongoose.model("Feature", featureSchema);

const productSchema = new mongoose.Schema({
   title: {
      type: String,
      required: true,
   },
   thumbnail: String,
   description: String,
   manufacture: { 
      type: mongoose.Schema.Types.ObjectId, 
      ref: "User" //< Capitalise the model name
   },
   featureHeaders: [{
      type: mongoose.Schema.Types.ObjectId,
      ref: "FeatureHeader", //< Reference the FeatureHeader model
   }],
   features: [{
      type: mongoose.Schema.Types.ObjectId,
      ref: "Feature", //< Reference the Feature model
   }],
},
{ timestamps: true });
// You need create the Feature model
const Product = mongoose.model("Product", productSchema);

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1. FeatureHeader和Feature需要单独保存在各自的集合中，以便引用。

const newFeatureOne = await Feature.create({
   title: 'Marvel',
});

const newFeatureHeader = await FeatureHeader.create({
   header: 'Superhero'
});

const newFeatureTwo = await Feature.create({
   title: 'Repulsor Beams',
   parentHeader: newFeatureHeader._id,
   parentFeature: newFeatureOne._id
});

const newProduct = await Product.create({
   title: 'Repulsor Beams',
   //...
   //... 
   featureHeaders: [newFeatureHeader._id],
   features: [newFeatureTwo._id],
});

型
1.现在，您可以调用populate来将ObjectId替换为相应的文档：

const id = req.body.id; //< Could be req.params.id or however you get the id

const product = await Product.findById(id)
   .populate("featureHeaders")
   .populate("features");

型

备注：根据您的设计以及模型的作用域，您可能需要指定populate选项对象的path和/或model属性，如下所示：

const id = req.body.id; //< Could be req.params.id or however you get the id

const product = await Product.findById(id)
   .populate({path: "featureHeaders", model: "FeatureHeader"})
   .populate({path: "features", model: "Feature"});

型
希望所有这些都是有意义的，如果你有任何问题，请在评论中提出。