feat(ConsoleSpanExporter): export span links

[trentm]

Which problem is this PR solving?

Currently the ConsoleSpanExporter does not include Span links, if the span happens to have any.

Short description of the changes

This PR adds span.links to the exported info.

As well, this changes the exporter to use console.dir(...) instead of console.log(...) so that the object depth can be set to 3, instead of the default 2. It is the difference between this (with console.log):

{
  traceId: '6f8d4df4cf914faaeaf99e958d788950',
  parentId: undefined,
  name: 'sLinksWithAttrs',
  id: 'e0b9b5d27579168d',
  kind: 0,
  timestamp: 1650492644954686,
  duration: 7,
  attributes: {},
  links: [ { context: [Object], attributes: [Object] } ],
  status: { code: 0 },
  events: []
}

and this (console.dir with depth 3):

{
  traceId: '48472434d1b96f48482761a3521b0d97',
  parentId: undefined,
  name: 'sLinksWithAttrs',
  id: '6fd6da8c3d98b995',
  kind: 0,
  timestamp: 1650492651408875,
  duration: 7,
  attributes: {},
  links: [
    {
      context: {
        traceId: '27d5c6b33e4bb5be49582ca14644e262',
        spanId: 'b88e2cb9c6a434bd',
        traceFlags: 1,
        traceState: undefined
      },
      attributes: { 'a.string': 'hi', 'a.number': 42 }
    }
  ],
  status: { code: 0 },
  events: []
}

This does mean an additional links: [] in the output of each span for the common case where there are no links. However, given ConsoleSpanExporter is for dev/debugging, that slight additional noise doesn't seem bad.

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Besides running this manually:

// consolelinks.js
const api = require('@opentelemetry/api')
const { NodeTracerProvider } = require('./packages/opentelemetry-sdk-trace-node') // '@opentelemetry/sdk-trace-node'
const { SimpleSpanProcessor, ConsoleSpanExporter } = require('./packages/opentelemetry-sdk-trace-base') // '@opentelemetry/sdk-trace-base'
const provider = new NodeTracerProvider()
provider.addSpanProcessor(new SimpleSpanProcessor(new ConsoleSpanExporter()))
provider.register()
const tracer = api.trace.getTracer('consolelinks')

const s1 = tracer.startSpan('sLinksNone')
s1.end()
const s2 = tracer.startSpan('sLinksWithAttrs', {
  links: [{ context: s1.spanContext(), attributes: { 'a.string': 'hi', 'a.number': 42 } }]
})
s2.end()

I also updated ConsoleSpanExporter.test.ts to expect a "links" key in the output.

Checklist:

• Followed the style guidelines of this project (at least I believe so)
• Unit tests have been added
• Documentation has been updated

[codecov]

Codecov Report

Merging #2917 (405580b) into main (28a177f) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2917   +/-   ##
=======================================
  Coverage   92.81%   92.81%           
=======================================
  Files         184      184           
  Lines        6066     6066           
  Branches     1296     1296           
=======================================
  Hits         5630     5630           
  Misses        436      436           

Impacted Files	Coverage Δ
...y-sdk-trace-base/src/export/ConsoleSpanExporter.ts	78.57% <100.00%> (ø)

[trentm]

Thanks!