仅合成单个CDK堆栈时因其他堆栈资源缺失报错的解决办法

我的CDK应用定义了两个堆栈，分别对应prod（生产）和dev（开发）环境。堆栈中定义的CloudFront函数，其构建文件路径会根据环境不同而变化：dev环境的函数包含基础认证逻辑（避免开发站点公开访问），prod环境则无此代码，对应路径分别为build-dev和build-prod。示例代码如下：

const cfViewerRequest = new cloudfront.Function(this, "MySite-CFViewerRequest", {
  code: cloudfront.FunctionCode.fromFile({filePath: `backend/functions/cf-viewer-request/build-${props.stage}/index.js`}),
  functionName: `MySite-CFViewerRequest-${props.stage}`,
  comment: `MySite-CFViewerRequest-${props.stage}`
});

入口代码会同时实例化两个堆栈：

#!/usr/bin/env node
import "source-map-support/register";
import * as cdk from "aws-cdk-lib";
import { MySiteStack } from "../lib/my-site-stack";

const app = new cdk.App();
new MySiteStack(app, "MySiteDev", {
  env: { account: "012345678901", region: "us-east-1" },
  stage: "dev",
});

new MySiteStack(app, "MySiteProd", {
  env: { account: "109876543210", region: "us-east-1" },
  stage: "prod",
});

问题：仅构建dev资源后，运行cdk synth MySiteDev会报错ENOENT: no such file or directory, open 'backend/functions/cf-viewer-request/build-prod/index.js'，因为CDK初始化时会创建所有堆栈实例，即使指定合成单个堆栈，也会执行prod堆栈的代码，尝试读取未构建的prod文件。

方案1：通过环境变量/命令行参数控制堆栈实例化 #

修改入口文件，根据环境变量或上下文参数，仅实例化当前需要的环境堆栈，避免CDK加载未使用的堆栈代码。

方式A：使用环境变量 #

修改入口代码：

#!/usr/bin/env node
import "source-map-support/register";
import * as cdk from "aws-cdk-lib";
import { MySiteStack } from "../lib/my-site-stack";

const app = new cdk.App();
// 从环境变量获取stage，默认dev
const stage = process.env.STAGE || "dev";

if (stage === "dev") {
  new MySiteStack(app, "MySiteDev", {
    env: { account: "012345678901", region: "us-east-1" },
    stage: "dev",
  });
} else if (stage === "prod") {
  new MySiteStack(app, "MySiteProd", {
    env: { account: "109876543210", region: "us-east-1" },
    stage: "prod",
  });
}

运行命令时指定环境变量：

# 合成dev堆栈
STAGE=dev cdk synth MySiteDev

# 合成prod堆栈
STAGE=prod cdk synth MySiteProd

方式B：使用CDK上下文参数 #

修改入口代码：

#!/usr/bin/env node
import "source-map-support/register";
import * as cdk from "aws-cdk-lib";
import { MySiteStack } from "../lib/my-site-stack";

const app = new cdk.App();
// 从CDK上下文获取stage，默认dev
const stage = app.node.tryGetContext("stage") || "dev";

if (stage === "dev") {
  new MySiteStack(app, "MySiteDev", {
    env: { account: "012345678901", region: "us-east-1" },
    stage: "dev",
  });
} else if (stage === "prod") {
  new MySiteStack(app, "MySiteProd", {
    env: { account: "109876543210", region: "us-east-1" },
    stage: "prod",
  });
}

运行命令时传递上下文参数：

# 合成dev堆栈
cdk synth MySiteDev -c stage=dev

# 合成prod堆栈
cdk synth MySiteProd -c stage=prod

方案2：使用独立入口文件 #

创建两个入口文件，分别对应dev和prod环境：

dev-app.js #

#!/usr/bin/env node
import "source-map-support/register";
import * as cdk from "aws-cdk-lib";
import { MySiteStack } from "../lib/my-site-stack";

const app = new cdk.App();
new MySiteStack(app, "MySiteDev", {
  env: { account: "012345678901", region: "us-east-1" },
  stage: "dev",
});

prod-app.js #

#!/usr/bin/env node
import "source-map-support/register";
import * as cdk from "aws-cdk-lib";
import { MySiteStack } from "../lib/my-site-stack";

const app = new cdk.App();
new MySiteStack(app, "MySiteProd", {
  env: { account: "109876543210", region: "us-east-1" },
  stage: "prod",
});

运行时指定入口文件：

# 合成dev堆栈
cdk synth MySiteDev -a "node dev-app.js"

# 合成prod堆栈
cdk synth MySiteProd -a "node prod-app.js"

方案3：使用惰性值延迟文件路径解析（可选） #

如果不想修改入口文件，可以使用CDK的Lazy值延迟文件路径的解析，只有当堆栈被实际合成时才会读取文件。注意：此方法需要确认CloudFront.FunctionCode.fromFile是否支持惰性值传递，部分CDK构造可能在初始化时就会尝试读取文件，导致此方法失效。

修改堆栈内的CloudFront函数代码：

import { Lazy } from "aws-cdk-lib";

// ...

const cfViewerRequest = new cloudfront.Function(this, "MySite-CFViewerRequest", {
  code: cloudfront.FunctionCode.fromFile({
    filePath: Lazy.string({
      produce: () => `backend/functions/cf-viewer-request/build-${props.stage}/index.js`
    })
  }),
  functionName: `MySite-CFViewerRequest-${props.stage}`,
  comment: `MySite-CFViewerRequest-${props.stage}`
});

内容的提问来源于stack exchange，提问作者Aaron J Spetner