Changing custom_schema file results in unexpected validation

[braingram]

Description of the problem

Overwriting a file used for custom_schema results in validation that uses the old file contents. This came up while attempting to use it in a jupyter notebook where this type of error seems likely to occur (as with any interactive session).

This may be due to schema caching. Perhaps not caching custom_schema would fix this.

Example of the problem

import asdf

schema_contents = """%YAML 1.1
---
id: "http://example.com/schemas/your-custom-schema"
$schema: "http://stsci.edu/schemas/yaml-schema/draft-01"
type: object
properties:
  value:
      type: integer"""


with open("my_schema.yaml", "w") as f:
    f.write(schema_contents)

af = asdf.AsdfFile(custom_schema="my_schema.yaml")
# af["value"] = "a"
# af.validate()  will correctly raise a ValidationError
af["value"] = 1
af.validate()

schema_contents = """%YAML 1.1
---
id: "http://example.com/schemas/your-custom-schema"
$schema: "http://stsci.edu/schemas/yaml-schema/draft-01"
type: object
properties:
  number:
      value: string"""

with open("my_schema.yaml", "w") as f:
    f.write(schema_contents)

af = asdf.AsdfFile(custom_schema="my_schema.yaml")
af["value"] = "a"
af.validate()  # incorrectly raise a ValidationError

System information

asdf version: main
python version: 3.10
operating system: mac