[WIP] output full bson objects MONGOSH-1285 #2584

lerouxb · 2025-11-20T15:43:16Z

I built this on top of @addaleax's wip branch, so the types are still mostly from there.

The short version of what we're trying to do: For BSON that we get from the database we want to print all of it, untruncated, when it gets evaluated or otherwise inspected with util.inspect().

This solution wraps the ServiceProvider with another class that implements all the same methods. Then:

all methods that return cursors have the returned cursors intercepted and the relevant methods on there that return documents replaced with new methods that recursively install our inspect function.
all methods that return promises of bson have their results intercepted and we recursively install our inspect function on the result.
all other methods are just forwarded with their results unchanged.

I have been testing it with this document which should be affected by the inspectOptions depth, maxArrayLength and maxStringLength:

db.test.insertOne({
  array: Array.from(Array(1000), (_,i) => i),
  string: 'All work and no play makes Jack a dull boy. '.repeat(250),
  object: {
    foo: {
      bar: {
        baz: {
          qux: {
            quux: {
              corge: {
                grault: 'If you can read this, you are too close.'
              }
            }
          }
        }
      }
    }
  }
});

And this doc has every BSON type which is useful for testing that we're not messing up existing BSON formatting:

db.test.insertOne({
    double: Double(1.2),
    doubleThatIsAlsoAnInteger: Double(1),
    string: 'Hello, world!',
    binData: Binary(Buffer.from([1, 2, 3])),
    boolean: true,
    date: Date('2023-04-05T13:25:08.445Z'),
    null: null,
    regex: BSONRegExp('pattern', 'i'),
    javascript: Code('function() {}'),
    symbol: BSONSymbol('symbol'),
    javascriptWithScope: Code('function() {}', { foo: 1, bar: 'a' }),
    int: Int32(12345),
    timestamp: Timestamp(Long('7218556297505931265')),
    long: Long('123456789123456789'),
    decimal: Decimal128(
      Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16])
    ),
    minKey: MinKey(),
    maxKey: MaxKey(),

    binaries: {
      generic: Binary(Buffer.from([1, 2, 3]), 0),
      functionData: Binary(Buffer.from('//8='), 1),
      binaryOld: Binary(Buffer.from('//8='), 2),
      uuidOld: Binary(Buffer.from('c//SZESzTGmQ6OfR38A11A=='), 3),
      uuid: UUID('AAAAAAAA-AAAA-4AAA-AAAA-AAAAAAAAAAAA'),
      md5: Binary(Buffer.from('c//SZESzTGmQ6OfR38A11A=='), 5),
      encrypted: Binary(Buffer.from('c//SZESzTGmQ6OfR38A11A=='), 6),
      compressedTimeSeries: Binary(
        Buffer.from(
          'CQCKW/8XjAEAAIfx//////////H/////////AQAAAAAAAABfAAAAAAAAAAEAAAAAAAAAAgAAAAAAAAAHAAAAAAAAAA4AAAAAAAAAAA==',
          'base64'
        ),
      ),
      custom: Binary(Buffer.from('//8='), 128),
    },

    dbRef: DBRef('namespace', ObjectId('642d76b4b7ebfab15d3c4a78')),
  });

You can test that the find cursor's tryNext was replaced by running:

> db.test.find()

(Notice that the whole array, string and object all printed.)

This will exercise the inspect function on the top-level array that was returned.

You can test that it recursively installed it on the documents inside that array by running:

> db.test.find().toArray()[0]

or even

> config.set('inspectDepth', 2);
> f = { a: { b: { c: { d: 1 } } } }
{ a: { b: { c: [Object] } } } # notice that it truncated
> db.test.find().toArray()[0].object # this will print the whole object, not just 2 levels

This needs a lot of tests. There are almost certainly some cases left that I've missed. And I'm unsure about some details. Just opening to have a discussion. Oh and we might want a way for users to opt out of it.

lerouxb · 2025-11-20T15:46:39Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+    // doesn't have readBufferedDocuments or toArray. We can try cast things to
+    // ServiceProviderAbstractCursor, but then that's not assignable to
+    // ServiceProviderAnyCursor. And that's why there's so much casting below.
+    const cursor = (this._sp[key] as any)(...args) as any;


I just had the thought that one obvious way around this is to just have cursorMethod() for regular cursors and changeCursorMethod() for change stream cursors. And just replace ReturnType<ServiceProvider[K]> with something a lot more specific. Then we can probably have much better type safety.

Right, although I think either way is fine here

lerouxb · 2025-11-20T15:47:39Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+const customInspectSymbol = Symbol.for('nodejs.util.inspect.custom');
+
+function cursorNext(
+  original: () => Promise<Document | null>


I can probably use some typescript to automatically pick this type off abstract cursor. Something like that. Same for the other cursor methods below.

lerouxb · 2025-11-20T15:48:26Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+  return async function (): Promise<Document | null> {
+    const result = await original();
+    if (result) {
+      replaceWithCustomInspect(result);


I just suddenly had the realisation that this is a terrible function name. addCustomInspect() rather?

I don't think it's that bad, but yes, addCustomInspect() sounds good 🙂

lerouxb · 2025-11-20T15:49:33Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+    this: DeepInspectServiceProviderWrapper,
+    ...args: Parameters<Required<ServiceProvider>[K]>
+  ): // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+  // @ts-ignore The returntype already contains a promise


A way around all this is to just make one function similar to bsonMethod() for each unique return type, kinda like what I did for the cursor methods.

lerouxb · 2025-11-20T15:50:09Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+    this: DeepInspectServiceProviderWrapper,
+    ...args: Parameters<Required<ServiceProvider>[K]>
+  ): ReturnType<Required<ServiceProvider>[K]> {
+    // not wrapping the result at all because forwardedMethod() is for simple


I made the decision here to leave everything that's not definitely a bson document or array alone. Make sense?

lerouxb · 2025-11-20T15:51:57Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+    maxStringLength: Infinity,
+  };
+
+  // reuse the standard inpect logic for an object without causing infinite


This feels very hacky, but I haven't thought of a better way to do it yet. I'm trying to avoid having to write my own function that will format an array or object exactly the way util.inspect() already does.

We know it's BSON, so it should be fine to use a shallow copy of the document/array, right?

lerouxb · 2025-11-20T15:53:43Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+    for (const item of obj) {
+      replaceWithCustomInspect(item);
+    }
+  } else if (obj && typeof obj === 'object' && obj !== null) {


Here, again, I made the decision to only touch arrays and documents/sub-documents and leave simple values alone. BUT this currently also installs our inspect function on BSON types like long, decimal, etc. Which we probably don't want?

What's the best way to do that? Look for obj._bsontype?

Ok for some reason this code doesn't mess up BSON object formatting 🤔 I suppose the prototype still has the BSONValue one? https://github.com/mongodb/js-bson/blob/main/src/bson_value.ts#L38

What's the best way to do that? Look for obj._bsontype?

We're pretty close to adopting BSON 7.x, where we have obj[bsonType] as a more reliable symbol property (but yeah, that's the best way to check for existing BSON objects)

…on on results

lerouxb · 2025-11-20T15:55:11Z

packages/shell-api/src/shell-instance-state.ts

        undefined,
        undefined,
-        initialServiceProvider
+        this.initialServiceProvider


btw it is VERY easy to accidentally pass initialServiceProvider (ie. the unwrapped value) to something in place of this.initialServiceProvider. Ask me how I know..

lerouxb · 2025-11-20T16:03:23Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+  return result;
+}
+
+function replaceWithCustomInspect(obj: any) {


Something obvious to note here: I'm mutating the obj in place rather than creating new objects. I did it that way for simplicity and because I'm worried about the impact on performance making a gazillion new objects, but admittedly I haven't profiled that yet. Let me know if you think there's a better way.

Yes, this should be fine 👍

addaleax · 2025-11-21T15:27:23Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+    // doesn't have readBufferedDocuments or toArray. We can try cast things to
+    // ServiceProviderAbstractCursor, but then that's not assignable to
+    // ServiceProviderAnyCursor. And that's why there's so much casting below.
+    const cursor = (this._sp[key] as any)(...args) as any;


Right, although I think either way is fine here

addaleax · 2025-11-21T15:28:05Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+    // ServiceProviderAnyCursor. And that's why there's so much casting below.
+    const cursor = (this._sp[key] as any)(...args) as any;
+
+    cursor.next = cursorNext(


I'd consider returning a wrapped cursor instead of modifying the existing one, if that's possible – like the wrapping for the ServiceProvider itself, this would make sure that we actually wrap all methods that we should and aren't forgetting about any

addaleax · 2025-11-21T15:28:43Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+
+    return results;
+  };
+}


^ All of these methods are essentially the same, no?

addaleax · 2025-11-21T15:29:08Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+  return async function (): Promise<Document | null> {
+    const result = await original();
+    if (result) {
+      replaceWithCustomInspect(result);


I don't think it's that bad, but yes, addCustomInspect() sounds good 🙂

addaleax · 2025-11-21T15:29:35Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+    this: DeepInspectServiceProviderWrapper,
+    ...args: Parameters<Required<ServiceProvider>[K]>
+  ): ReturnType<Required<ServiceProvider>[K]> {
+    // not wrapping the result at all because forwardedMethod() is for simple


addaleax · 2025-11-21T15:30:22Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+    maxStringLength: Infinity,
+  };
+
+  // reuse the standard inpect logic for an object without causing infinite


We know it's BSON, so it should be fine to use a shallow copy of the document/array, right?

addaleax · 2025-11-21T15:30:42Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+  return result;
+}
+
+function replaceWithCustomInspect(obj: any) {


Yes, this should be fine 👍

addaleax · 2025-11-21T15:31:17Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+
+function replaceWithCustomInspect(obj: any) {
+  if (Array.isArray(obj)) {
+    (obj as any)[customInspectSymbol] = customDocumentInspect;


Suggested change

(obj as any)[customInspectSymbol] = customDocumentInspect;

(obj as any)[customInspectSymbol] ??= customDocumentInspect;

maybe unnecessarily defensive, but if something already has a custom inspect function for some reason, we can probably leave that in place

addaleax · 2025-11-21T15:32:33Z

packages/shell-api/src/deep-inspect-service-provider-wrapper.ts

+    for (const item of obj) {
+      replaceWithCustomInspect(item);
+    }
+  } else if (obj && typeof obj === 'object' && obj !== null) {


What's the best way to do that? Look for obj._bsontype?

We're pretty close to adopting BSON 7.x, where we have obj[bsonType] as a more reliable symbol property (but yeah, that's the best way to check for existing BSON objects)

WIP

40a8727

lerouxb commented Nov 20, 2025

View reviewed changes

use DeepInspectServiceProviderWrapper, install our own inspect functi…

4b2991c

…on on results

lerouxb force-pushed the print-output-full branch from 2428a91 to 4b2991c Compare November 20, 2025 15:54

lerouxb commented Nov 20, 2025

View reviewed changes

lerouxb added 2 commits November 20, 2025 16:50

you cannot extend the return value of initializeBulkOp

f85dc9f

apparently inspect passed as the final parameter isn't always a thing

24ef043

lerouxb mentioned this pull request Nov 21, 2025

feat(cli-repl): warn when util.inspect() truncated output MONGOSH-1285 #2585

Draft

addaleax reviewed Nov 21, 2025

View reviewed changes

	(obj as any)[customInspectSymbol] = customDocumentInspect;
	(obj as any)[customInspectSymbol] ??= customDocumentInspect;

[WIP] output full bson objects MONGOSH-1285 #2584

Are you sure you want to change the base?

[WIP] output full bson objects MONGOSH-1285 #2584

Uh oh!

Conversation

lerouxb commented Nov 20, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

lerouxb Nov 20, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

lerouxb Nov 20, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

lerouxb commented Nov 20, 2025 •

edited

Loading

lerouxb Nov 20, 2025 •

edited

Loading

lerouxb Nov 20, 2025 •

edited

Loading