Default values for jsconfig.json override extended values

TypeScript Version: 3.8.0-dev.20200207

Search Terms: jsconfig extend override defaults

Code

// a/jsconfig.json
{
  "files": ["test.js"],
  "compilerOptions": {
    "maxNodeModuleJsDepth": 0
  }
}

// b/jsconfig.json
{
  "extends": "../a/jsconfig.json"
}

// a/test.js
console.log("hello");

Reproduce

mkdir -p a b
echo '{"files":["test.js"],"compilerOptions":{"maxNodeModuleJsDepth":0}}' > a/jsconfig.json
echo '{"extends":"../a/jsconfig.json"}' > b/jsconfig.json
echo 'console.log("hello");' > a/test.js

npx tsc -p a/jsconfig.json --showConfig
npx tsc -p b/jsconfig.json --showConfig

Expected behavior:
Both implied configs A and B have compilerOptions.maxNodeModuleJsDepth: 0.

Actual behavior:
Implied config A has compilerOptions.maxNodeModuleJsDepth: 0.
Implied config B has compilerOptions.maxNodeModuleJsDepth: 2.
Output:

{
    "compilerOptions": {
        "allowJs": true,
        "maxNodeModuleJsDepth": 0,
        "allowSyntheticDefaultImports": true,
        "skipLibCheck": true,
        "noEmit": true
    },
    "files": [
        "./test.js"
    ]
}
{
    "compilerOptions": {
        "allowJs": true,
        "maxNodeModuleJsDepth": 2,
        "allowSyntheticDefaultImports": true,
        "skipLibCheck": true,
        "noEmit": true
    },
    "files": [
        "../a/test.js"
    ]
}

Implied config B has maxNodeModuleJsDepth: 2 despite it extending config A which explicitly sets maxNodeModuleJsDepth: 0.

Possible cause
This may be caused by the default values for config files named jsconfig.json overriding the values from the extended config. maxNodeModuleJsDepth: 2 is one of the default values. See: /src/compiler/commandLineParser.ts#L2459

Solution
Default values for jsconfig.json config files should not override values explicitly defined by the extended configs.

Workaround
Explicitly set the following values in config files named jsconfig.json that extend other configs with non-default values:

• allowJs
• maxNodeModuleJsDepth
• allowSyntheticDefaultImports
• skipLibCheck
• noEmit

从 src/compiler/commandLineParser.ts 中 issue 提到的 jsconfig 默认值处理开始。使用两个配置复现问题，并分别比较 npx tsc -p ... --showConfig 的结果。完成的标准是：扩展配置中显式定义的值会被保留，而不是被 jsconfig 默认值替换。