Support changing dataType for a binding in v4

[ejizba]

v3 function.json content:

{
    "name": "myQueueItem",
    "type": "queueTrigger",
    "direction": "in",
    "queueName": "helloworldqueue",
    "connection": "storage_APPSETTING",
    "dataType": "binary"
}

v3 index.js content:

module.exports = async function (context, myQueueItem) {
    context.log('JavaScript queue trigger function processed work item', myQueueItem);
};

In v3 the type of myQueueItem changes based on the value of dataType. If you set dataType to binary, myQueueItem will be a Buffer. Otherwise, myQueueItem will either be a string or possibly a parsed object if the string was JSON.

In v4, we don't allow users to change myQueueItem to a Buffer type, which we should. This does not apply to http triggers, but probably applies to several other triggers/bindings other than storage queue.

[vsantele]

Is there any news on this issue? Or a way to help fix it?

[ejizba]

No updates, but this is still planned to be fixed before we GA. For a workaround, either use the v3 model or use generics:

import { app, InvocationContext, trigger } from "@azure/functions";

export async function storageQueueTrigger1(queueItem: unknown, context: InvocationContext): Promise<void> {
    context.log(`Is it a buffer? ${Buffer.isBuffer(queueItem)}`);
}

app.generic('storageQueueTrigger1', {
    trigger: trigger.generic({
        type: 'queueTrigger',
        queueName: 'testqueue',
        connection: 'storage_APPSETTING',
        dataType: 'binary'
    }),
    handler: storageQueueTrigger1
});

[sinedied]

Bumping into this, I have a storage extra input trying to load a PDF file, and I cannot get the blob content as a binary.

@ejizba is there a workaround when using the v4 extraInputs for setting the dataType?

[ejizba]

This has been de-prioritized in favor of a feature that uses @azure/storage-blob sdk types, where basically we would give you a BlobClient as the trigger input or extra input and you can use the client to get the content however you want. @castrodd is working on a prototype now, related to #99 and #203

In the meantime, the only workaround for extra inputs is to use the sdk and create the blob client yourself. There is no workaround for trigger inputs. Actually, I already mentioned a workaround above using generics, that should still work for both.

[sinedied]

Thanks for the details! I ended up using @azure/storage-blob but I like to try using any opportunity to reduce/simplify code 🙂 I'll have a look at generics, seems like a nice workaround.

[rohsyl]

As its still not fixed yet you can use this workaround :

app.eventHub('LiveData', {
    connection: '...',
    eventHubName: 'messages/events',
    cardinality: 'many',
    consumerGroup: '%...%',
    handler: ...,
    dataType: 'binary',
} as any);

add the dataType and simply force cast as any and it works. it looks like it's just a typescript definition issue.