"Invalid attribute value set for key" when serializing array of objects

[isaac-s]

Using SDK 3.9.0 with Winston 3.17.0, the following results in Invalid attribute value set for key: x [].

const appInsights = require("applicationinsights");

appInsights
  .setup(process.env.APPLICATIONINSIGHTS_CONNECTION_STRING)
  .setAutoCollectConsole(true, true)
  .start();

const winston = require("winston");

const logger = winston.createLogger({
  transports: [
    new winston.transports.Console()
  ]
});

logger.info("hello", {
  x: [{
    a: "b",
  }]
});

appInsights.flushAzureMonitor().then();

[rads-1996]

@isaac-s After reviewing the issue, we found that the attributes you're passing logger.info as -

x: [{ a: "b"}]

are being evaluated for their type. The type for {a: 'b'} is classified as an object, it doesn't meet the criteria defined in the isValidPrimitiveAttributeValue method within attributes.js- https://github.com/open-telemetry/opentelemetry-js/blob/cb868d74a4f48798f6b859f2034afb2b8630e01c/packages/opentelemetry-core/src/common/attributes.ts#L19, which currently only accepts strings, booleans, or numbers. As a result, the object is considered invalid and triggers the error you encountered. This validation logic comes from upstream OpenTelemetry.