oss_24_declarative_config_present_null_defaults #31

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1. ocelotl commented on Jul 22, 2026

   

   ocelotl

   on Jul 22, 2026

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   🔒 Internal (dash0) — not for upstream.

   • Linear: https://linear.app/dash0/issue/OSS-24/l1-declarative-config-present-but-null-components-fail-instead-of (finding L1)
   • Slug/branch/worktree: oss_24_declarative_config_present_null_defaults
   • Commit: 9e7d6534b · PR: oss_24_declarative_config_present_null_defaults #34
   • Validation: opentelemetry-configuration suite 369 passed; scope package + changelog.
2. ocelotl commented on Jul 22, 2026

   

   ocelotl

   on Jul 22, 2026

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   📣 Public-facing draft — to be opened upstream in open-telemetry/opentelemetry-python. No internal references; copy verbatim.

   Title: Declarative config: present-but-null component value raises instead of building with defaults

   Description

   In the declarative configuration package (opentelemetry-configuration), a YAML/JSON value that is present but null is indistinguishable from a completely absent key after parsing, so a present-null component fails to build.

   Evidence

   opentelemetry-configuration/src/opentelemetry/configuration/_conversion.py (_convert_value) returned None for any None value:

   if value is None:
       return None

   Component factories select the configured component by testing value is not None, e.g. _tracer_provider.py (~L205-217):

   for name, factory in _SPAN_EXPORTER_REGISTRY.items():
       value = getattr(config, name, None)
       if value is not None:
           return factory(value)
   ...
   raise ConfigurationError("No exporter type specified in span exporter config. ...")

   The same pattern exists in _logger_provider.py, _meter_provider.py, _propagator.py, and _common.py:_resolve_component. A present-null console: converts to None, so if value is not None is false and the code raises ConfigurationError instead of building a console exporter with defaults.

   Reproduction

   tracer_provider:
     processors:
       - batch:
           exporter:
             console:   # present but null

   Raises ConfigurationError: No exporter type specified... instead of creating a ConsoleSpanExporter with defaults.

   Spec

   configuration/sdk.md: Parse MUST distinguish a missing key from a present-null one; a present-null component MUST be created with defaults. Java and Go bind a present-null node to the raw (empty) model node and construct with defaults.

   Proposed fix

   Carry a present-null indicator through conversion. Since _convert_value is only invoked for keys actually present (absent keys fall through to dataclass field defaults), a None there always means present-null. Convert it to a component-with-defaults value: a defaults-only dataclass instance for dataclass-typed fields, an empty mapping for mapping-alias fields (e.g. the console exporter), and None for primitives. Existing value is not None factory selection then fires for present-null while absent keys stay None.
3. ocelotl commented on Aug 7, 2026

   

   ocelotl

   on Aug 7, 2026

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   Superseded by upstream open-telemetry#5454; PR #34 closed. Present-null-builds-with-defaults is implemented on upstream/main.
4. ocelotl

   closed this as completedon Aug 7, 2026