Revert PR #378 (Simplify NotebookNotary._data_dir_default) (#397)

* Revert PR #378 (Simplify NotebookNotary._data_dir_default)

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

nbformat/sign.py

@@ -14,8 +14,6 @@
 from hmac import HMAC
 from pathlib import Path
 
-from jupyter_core.paths import jupyter_data_dir
-
 try:
     import sqlite3
 
@@ -41,7 +39,7 @@ def convert_datetime(val):
 
 from jupyter_core.application import JupyterApp, base_flags
 from traitlets import Any, Bool, Bytes, Callable, Enum, Instance, Integer, Unicode, default, observe
-from traitlets.config import LoggingConfigurable
+from traitlets.config import LoggingConfigurable, MultipleInstanceError
 
 from . import NO_CONVERT, __version__, read, reads
 
@@ -343,7 +341,17 @@ class NotebookNotary(LoggingConfigurable):
 
     @default("data_dir")
     def _data_dir_default(self):
-        return jupyter_data_dir()
+        app = None
+        try:
+            if JupyterApp.initialized():
+                app = JupyterApp.instance()
+        except MultipleInstanceError:
+            pass
+        if app is None:
+            # create an app, without the global instance
+            app = JupyterApp()
+            app.initialize(argv=[])
+        return app.data_dir
 
     store_factory = Callable(
         help="""A callable returning the storage backend for notebook signatures.

package.json

@@ -1,25 +1,25 @@
 {
-    "name": "nbformat-schema",
-    "version": "5.10.2",
-    "description": "JSON schemata for Jupyter notebook formats",
-    "main": "index.js",
-    "files": [
-        "nbformat/v3/nbformat.v3.schema.json",
-        "nbformat/v4/nbformat.v4.schema.json"
-    ],
-    "repository": {
-        "type": "git",
-        "url": "git+https://github.com/jupyter/nbformat.git"
-    },
-    "keywords": [
-        "jupyter",
-        "notebook",
-        "json-schema"
-    ],
-    "author": "Project Jupyter Contributors",
-    "license": "BSD-3-Clause",
-    "bugs": {
-        "url": "https://github.com/jupyter/nbformat/issues"
-    },
-    "homepage": "https://nbformat.readthedocs.io"
+  "name": "nbformat-schema",
+  "version": "5.10.2",
+  "description": "JSON schemata for Jupyter notebook formats",
+  "main": "index.js",
+  "files": [
+    "nbformat/v3/nbformat.v3.schema.json",
+    "nbformat/v4/nbformat.v4.schema.json"
+  ],
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/jupyter/nbformat.git"
+  },
+  "keywords": [
+    "jupyter",
+    "notebook",
+    "json-schema"
+  ],
+  "author": "Project Jupyter Contributors",
+  "license": "BSD-3-Clause",
+  "bugs": {
+    "url": "https://github.com/jupyter/nbformat/issues"
+  },
+  "homepage": "https://nbformat.readthedocs.io"
 }