Raise error when loading schema with bad prefix

.github/workflows/ci.yaml

@@ -35,6 +35,9 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
+        with:
+          submodules: true
+
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v4
         with:
@@ -64,6 +67,9 @@ jobs:
         run: |
           HED_GITHUB_TOKEN=${{ secrets.HED_GITHUB_TOKEN }} coverage run -m unittest
 
+      - name: Run spec_test coverage
+        run: HED_GITHUB_TOKEN=${{ secrets.HED_GITHUB_TOKEN }} coverage run --append -m unittest spec_tests/test_errors.py
+
       - name: Archive code coverage results
         if: ${{matrix.python-version == '3.9'}}
         uses: actions/upload-artifact@v3

hed/errors/exceptions.py

@@ -26,6 +26,8 @@ class HedExceptions:
     ROOTED_TAG_HAS_PARENT = "SCHEMA_LIBRARY_INVALID"
     ROOTED_TAG_DOES_NOT_EXIST = "SCHEMA_LIBRARY_INVALID"
     IN_LIBRARY_IN_UNMERGED = "SCHEMA_LIBRARY_INVALID"
+    INVALID_LIBRARY_PREFIX = "SCHEMA_LIBRARY_INVALID"
+
 
     SCHEMA_VERSION_INVALID = 'SCHEMA_VERSION_INVALID'
     SCHEMA_SECTION_MISSING = 'SCHEMA_SECTION_MISSING'

hed/schema/hed_schema.py

@@ -9,6 +9,7 @@
 from hed.errors import ErrorHandler
 from hed.errors.error_types import ValidationErrors
 from hed.schema.hed_schema_base import HedSchemaBase
+from hed.errors.exceptions import HedFileError, HedExceptions
 
 
 class HedSchema(HedSchemaBase):
@@ -265,10 +266,17 @@ def set_schema_prefix(self, schema_namespace):
         Parameters:
             schema_namespace (str): Should be empty, or end with a colon.(Colon will be automated added if missing).
 
+        :raises HedFileError:
+            - The prefix is invalid
         """
         if schema_namespace and schema_namespace[-1] != ":":
             schema_namespace += ":"
 
+        if schema_namespace and not schema_namespace[:-1].isalpha():
+            raise HedFileError(HedExceptions.INVALID_LIBRARY_PREFIX,
+                               "Schema namespace must contain only alpha characters",
+                               self.filename)
+
         self._namespace = schema_namespace
 
     def __eq__(self, other):

hed/schema/hed_schema_io.py

@@ -111,8 +111,8 @@ def _load_schema_version(xml_version=None, xml_folder=None):
     """ Return specified version or latest if not specified.
 
     Parameters:
-        xml_folder (str): Path to a folder containing schema.
         xml_version (str): HED version format string. Expected format: '[schema_namespace:][library_name_]X.Y.Z'.
+        xml_folder (str): Path to a folder containing schema.
 
     Returns:
         HedSchema or HedSchemaGroup: The requested HedSchema object.
@@ -121,6 +121,7 @@ def _load_schema_version(xml_version=None, xml_folder=None):
         - The xml_version is not valid.
         - The specified version cannot be found or loaded
         - Other fatal errors loading the schema (These are unlikely if you are not editing them locally)
+        - The prefix is invalid
     """
     schema_namespace = ""
     library_name = None
@@ -164,14 +165,17 @@ def load_schema_version(xml_version=None, xml_folder=None):
                                            An empty string returns the latest version
                                            A json str format is also supported,
                                            based on the output of HedSchema.get_formatted_version
+                                           Basic format: '[schema_namespace:][library_name_]X.Y.Z'.
         xml_folder (str): Path to a folder containing schema.
 
     Returns:
         HedSchema or HedSchemaGroup: The schema or schema group extracted.
 
     :raises HedFileError:
         - The xml_version is not valid.
-        - A fatal error was encountered in parsing
+        - The specified version cannot be found or loaded
+        - Other fatal errors loading the schema (These are unlikely if you are not editing them locally)
+        - The prefix is invalid
     """
     # Check if we start and end with a square bracket, or double quote.  This might be valid json
     if xml_version and isinstance(xml_version, str) and \