Add proper error handling and wrapping

[dankochetov]

[kibertoad]

What is missing?

[probablykasper]

Is this for returning errors, so we can prevent bugs from forgetting to handle exceptions and from incorrectly guessing the error type?

[fermentfan]

This would be super helpful for our code quality. I noticed this when Drizzle threw me an error, when I tested our API with a wrong resource ID to test if the 404 works. Postgres was already mad, because the wrong ID wasn't a valid UUIDv4. Catching this now and throwing an appropriate 404 is kinda smelly.

Error codes would be nice to have!

[swelham]

Another example of how error handling could improve code quality is with errors raised from constraints.

For example, when see a unique containst error, we get a fairly raw looking error object in our try..catch(e).

{
  code: '23505'
  column: undefined
  constraint: 'users_email_index'
  dataType: undefined
  detail: 'Key (email)=(user@example.com) already exists.'
  file: 'nbtinsert.c'
  hint: undefined
  internalPosition: undefined
  internalQuery: undefined
  length: 231
  line: '664'
  name: 'error'
  position: undefined
  routine: '_bt_check_unique'
  schema: 'public'
  severity: 'ERROR'
  table: 'users'
  where: undefined
  message: 'duplicate key value violates unique constraint "users_email_index"'
  stack: <stacktrace_goes_here>
}

We then need to check that certain properties exist with specific values to determine what type of error it was.

A few options are:

// Check the constraint name or message
e.constraint === 'users_email_index';
//or
e.message === 'duplicate key value violates unique constraint "users_email_index"';

// Checking the detail field with a regex
const rx = new RegExp(/Key \(email\).*already exists/);
rx.test(e.detail);

// Checking more internal specifics
e.routine === '_bt_check_unique';

It would be really nice to have some higher level type that hides the internals and allows for simpler use within a catch statement.

[algora-pbc]

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[rishi-raj-jain]

What's the exactly scope of this? @john-griffin

[kesh-007]

Is the issue still open? I am interested in working on this.

[swelham]

Hey. Yes this is still open.

From this issue we (@john-griffin and myself) are hoping to achieve a higher level error to work with that has better support for typescript. For example, looking at my comment above, all of the examples rely on checking strings for certain values in a way that doesn't allow us to capture typos at compile time.

I don't have a firm solution and maybe the drizzle team can make some recommendations here, but if we could achieve a type safe way to check for expected database errors, that would achieve the scope of the bounty.

Here are some rough ideas that we have discussed, but are by no means prescriptive.

// Generic error class
class QueryError extends Error {
  type: "NonNull" | "UniqueConstraint" | "CheckConstraint" | "ForeignKey" // etc...
  table: string; // Can this be typed to all known tables
  field: string; // Can this by typed to all known fields
  message: string;
}

// or

// Error type specific error classes
class UniqueConstraintError extends Error {
  table: string; // Can this be typed to all known tables
  field: string; // Can this by typed to all known fields
  message: string;
}
class NonNullError extends Error {
  table: string; // Can this be typed to all known tables
  field: string; // Can this by typed to all known fields
  message: string;
}

Something like this would allow checking for errors without dealing directly with the error class from the pg module and could potentially allow better typing.

catch (e) {
  if (e instanceof QueryError) {
    if (e.type === 'unique' and e.field === 'email') { ... }
    if (e.type === 'unknown_type' and e.field === 'email') { ... } // < type error
  }
}

// or

catch (e) {
  if (e instanceof UniqueConstraintError) {
    if (e.field === 'email') { ... }
    if (e.field === 'unknown_field') { ... } // < type error
  }  
}

Again, happy to defer to the drizzle team for API specific guidance.