[pkg/ottl] Map literals within slices can not be parsed

[bacherfl]

Component(s)

pkg/ottl

What happened?

Description

Currently, it is not possible to pass a slice containing map literals to OTTL. This is because the mapGetter returns a pcommon.Map instead of a map[string]any:

opentelemetry-collector-contrib/pkg/ottl/expression.go

Lines 196 to 199 in 8034e0d

	result := pcommon.NewMap()
	if err := result.FromRaw(evaluated); err != nil {
	return nil, err
	}

If a map literal then happens to be within a slice, eventually the pcommon.Slice.FromRaw() method will be invoked, which however only can handle raw types for its elements: https://github.com/open-telemetry/opentelemetry-collector/blob/6740a28a8003a534c20c2608d760edd015657622/pdata/pcommon/value.go#L134-L178

Steps to Reproduce

Start the collector with the following config:

receivers:
  otlp:
    protocols:
      grpc:
        endpoint: 0.0.0.0:4317
      http:
        endpoint: 0.0.0.0:4318
processors:
  transform:
    error_mode: ignore
    trace_statements:
      - context: span
        statements:
          - set(attributes["test"], {"list":[{"foo":"bar"}]})

exporters:
  debug:
    verbosity: detailed

service:
  pipelines:
    traces:
      receivers: [otlp]
      processors: [transform]
      exporters: [debug]

And send some test data to it, e.g. with telemetrygen:

telemetrygen traces --otlp-insecure --traces 1 --status-code Ok --span-duration 1s

Expected Result

The test attribute should be added to the span

Actual Result

The attribute is not added, due to the following error logged by the collector:

ottl/parser.go:365      failed to execute statement     {"kind": "processor", "name": "transform", "pipeline": "traces", "error": "<Invalid value type pcommon.Map>", "statement": "set(attributes[\"test\"], {\"list\":[{\"foo\":\"bar\"}]})"}

Collector version

v0.117.0

Environment information

Environment

OS: macOS
Compiler(if manually compiled): go 1.22

OpenTelemetry Collector configuration

receivers:
  otlp:
    protocols:
      grpc:
        endpoint: 0.0.0.0:4317
      http:
        endpoint: 0.0.0.0:4318
processors:
  transform:
    error_mode: ignore
    trace_statements:
      - context: span
        statements:
          - set(attributes["test"], {"list":[{"foo":"bar"}]})

exporters:
  debug:
    verbosity: detailed

service:
  pipelines:
    traces:
      receivers: [otlp]
      processors: [transform]
      exporters: [debug]

Log output

Additional context

I already have a draft for a fix ready that I can provide

[github-actions]

Pinging code owners:

• pkg/ottl: @TylerHelmuth @kentquirk @bogdandrutu @evan-bradley @edmocosta

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