Validate Extension Declarations in SigMF Files

Issue

Extensions used in SigMF metadata must be declared in the global core:extensions field, but the validator wasn't checking for undeclared extensions.

Changes

Added validation to ensure all extension namespaces used in the metadata are properly declared in global:core:extensions. The validator now:

1. Extracts declared extension namespaces from global:core:extensions
2. Scans through all metadata sections (global, captures, annotations) to find extension namespaces in use
3. Raises a ValidationError if any extensions are used without being declared

Example

This will now fail validation:

{
"global": {
"core:datatype": "cf32_le",
"core:version": "1.0.0"
},
"captures": [{
"core:sample_start": 0,
"foo:some_field": 123 # Using undeclared 'foo' extension
}]
}

To fix, declare the extension:

{
"global": {
"core:datatype": "cf32_le",
"core:version": "1.0.0",
"core:extensions": [{
"name": "foo",
"version": "1.0.0",
"optional": true
}]
},
"captures": [{
"core:sample_start": 0,
"foo:some_field": 123 # Now properly declared
}]
}

Testing

• Added tests to verify validation fails when extensions are used without declaration
• Added tests to verify validation passes when extensions are properly declared
• Tested with multiple extensions and nested fields

Related Issues

Implements feature request from monthly SigMF call to validate extension declarations as in issue and closes #103