Compatibility with marshmallow 4

.travis.yml

@@ -5,7 +5,6 @@ env:
 - MARSHMALLOW_VERSION="==3.0.0"
 - MARSHMALLOW_VERSION=""
 python:
-- '3.6'
 - '3.8'
 before_install:
 - travis_retry pip install codecov

flask_apispec/apidoc.py

@@ -1,20 +1,17 @@
 import copy
 import functools
 
-import apispec
 from apispec.core import VALID_METHODS
 from apispec.ext.marshmallow import MarshmallowPlugin
 
 from marshmallow import Schema
-from marshmallow.utils import is_instance_or_subclass
 
 from flask_apispec.paths import rule_to_path, rule_to_params
-from flask_apispec.utils import resolve_resource, resolve_annotations, merge_recursive
-
-APISPEC_VERSION_INFO = tuple(
-    [int(part) for part in apispec.__version__.split('.') if part.isdigit()]
+from flask_apispec.utils import (
+    is_instance_or_subclass, resolve_resource, resolve_annotations, merge_recursive
 )
 
+
 class Converter:
     def __init__(self, app, spec, document_options=True):
         self.app = app

flask_apispec/utils.py

@@ -99,3 +99,10 @@ def _merge_recursive(child, parent):
             for key in keys
         }
     return child if child is not None else parent
+
+
+def is_instance_or_subclass(val, class_):
+    try:
+        return issubclass(val, class_)
+    except TypeError:
+        return isinstance(val, class_)

flask_apispec/wrapper.py

@@ -1,17 +1,16 @@
 from flask import Response
 
+import importlib.metadata
 from collections.abc import Mapping
 
 import flask
-import marshmallow as ma
 import werkzeug
+from packaging.version import Version
 from webargs import flaskparser
 
 from flask_apispec import utils
 
-MARSHMALLOW_VERSION_INFO = tuple(
-    [int(part) for part in ma.__version__.split('.') if part.isdigit()]
-)
+MARSHMALLOW_VERSION = Version(importlib.metadata.version("marshmallow"))
 
 
 class Wrapper:
@@ -60,7 +59,7 @@ def marshal_result(self, result, status_code):
         if schema and annotation.apply is not False:
             schema = utils.resolve_schema(schema['schema'], request=flask.request)
             dumped = schema.dump(result)
-            output = dumped.data if MARSHMALLOW_VERSION_INFO[0] < 3 else dumped
+            output = dumped.data if MARSHMALLOW_VERSION.major < 3 else dumped
         else:
             output = result
 

setup.py

@@ -48,7 +48,8 @@ def read(fname):
     license='MIT',
     zip_safe=False,
     keywords='flask marshmallow webargs apispec',
-    python_requires=">=3.6",
+    python_requires=">=3.8",
+    dependencies=["packaging>=17.0"],
     test_suite='tests',
     project_urls={
         'Bug Reports': 'https://github.com/jmcarp/flask-apispec/issues',