mdatagen cannot generate histogram correctly

[coderdjw]

Component(s)

cmd/mdatagen

What happened?

Describe the bug
I am using mdatagen v0.142.x. I am trying to modify https://github.com/open-telemetry/opentelemetry-collector/blob/main/cmd/mdatagen/internal/samplescraper/metadata.yaml and add a metric using histogram.

mdatagen --version
mdatagen version v0.142.1-0.20251224170331-6282405c5fee+dirty

  system.cpu.utilization:
    enabled: true
    stability:
      level: beta
    description: Gauge double metric enabled by default.
    extended_documentation: The metric will be become optional soon.
    unit: "1"
    histogram:
      value_type: double
      bucket_boundaries: [0.0, 0.25, 0.5, 0.75, 1.0]

But I found the generated_metrics.go has syntax issue and seems histogram report function is not correctly generated.

Steps to reproduce
Change https://github.com/open-telemetry/opentelemetry-collector/blob/main/cmd/mdatagen/internal/samplescraper/metadata.yaml and add above section, then run go generate

$ [open-telemetry/opentelemetry-collector/cmd/mdatagen/internal/samplescraper]: go generate ./...

Then check opentelemetry-collector/cmd/mdatagen/internal/samplescraper/internal/metadata/generated_metrics.go.

What did you expect to see?

What did you see instead?

Collector version

b579eb1

Environment information

Environment

go version go1.25.5 linux/amd64

OpenTelemetry Collector configuration

Log output

Additional context

No response

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Pinging code owners:

• cmd/mdatagen: @dmitryax

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