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I am writing a spoof of the `fs` module; the actual storage mechanism is not the the filesystem but rather a database. Overall, however, the api will function exactly like `fs`.

So far my code is comparable to the following:

```
let underlyingDb = require('module-for-accessing-db');

let mockFs = {
  
  promises: {
    
    readFile: async (fp, opts) => {
      let pk = convertFpToPk(fp);
      let res = await underlyingDb.query('SELECT * FROM "MockFs" WHERE "pk"=$1', [ pk ]);
      
      // Mock potential fs error:
      if (!res.rows.length) throw new Error(`ENOENT: no such file or directory...`);
      
      // TODO: check `opts` to see which encoding is desired
      return res.rows[0].fileContent;
    },
    writeFile: async (fp, data, opts) => {
      // Same idea as readFile, but with an INSERT ON CONFLICT statement
      // instead of SELECT...
    }
    
  },
  
  readFileSync: () => { /* ... */ }
  
};
```

As you can see it is straightforward for me to mock async file reading and writing.

I am now wondering, however, if it is possible to mock the `*Sync` methods in `fs`. Importantly, `module-for-accessing-db` *only* provides async access methods!

My initial instinct was to try the following (warning: gross!):

```
{
  readFileSync: (fp, data) => {
    let result = null;
    let err = null;
    
    (async () => {
      try {
        result = await mockFs.promises.readFile(fp, data);
      } catch(err0) {
        err = err0;
      }
    })();
    
    while (result === null && err === null) {} // Ew!!
    
    if (err) throw err;
    return result;
  }
}

```

Of course, this doesn't work. The `while` loop chokes out the entire event loop making it impossible for `result` or `err` to ever become set, even if the async database queries complete.

What are my options here? Do I need to switch the module I'm using to access the db? Do I need to write C code? Or is there a really clever technique to directly solve this problem, using only nodejs?

Nodejs wrap async function in synchronous function

I am writing a spoof of the `fs` module; the actual storage mechanism is not the the filesystem but rather a database. Overall, however, the api will function exactly like `fs`.

So far my code is comparable to the following:

```
let underlyingDb = require('module-for-accessing-db');

let mockFs = {
  
  promises: {
    
    readFile: async (fp, opts) => {
      let pk = convertFpToPk(fp);
      let res = await underlyingDb.query('SELECT * FROM "MockFs" WHERE "pk"=$1', [ pk ]);
      
      // Mock potential fs error:
      if (!res.rows) throw new Error(`ENOENT: no such file or directory...`);
      
      // TODO: check `opts` to see which encoding is desired
      return res.rows[0].fileContent;
    },
    writeFile: async (fp, data, opts) => {
      // Same idea as readFile, but with an INSERT ON CONFLICT statement
      // instead of SELECT...
    }
    
  },
  
  readFileSync: () => { /* ... */ }
  
};
```

As you can see it is straightforward for me to mock async file reading and writing.

I am now wondering, however, if it is possible to mock the `*Sync` methods in `fs`. Importantly, `module-for-accessing-db` *only* provides async access methods!

My initial instinct was to try the following (warning: gross!):

```
{
  readFileSync: (fp, data) => {
    let result = null;
    let err = null;
    
    (async () => {
      try {
        result = await mockFs.promises.readFile(fp, data);
      } catch(err0) {
        err = err0;
      }
    })();
    
    while (result === null && err === null) {} // Ew!!
    
    if (err) throw err;
    return result;
  }
}

```

Of course, this doesn't work. The `while` loop chokes out the entire event loop making it impossible for `result` or `err` to ever become set, even if the async database queries complete.

What are my options here? Do I need to switch the module I'm using to access the db? Do I need to write C code? Or is there a really clever technique to directly solve this problem, using only nodejs?