Raise exception when trying to commit folder-based journal (including DayOne)

jrnl/DayOneJournal.py

@@ -32,6 +32,7 @@ class DayOne(Journal.Journal):
     def __init__(self, **kwargs):
         self.entries = []
         self._deleted_entries = []
+        self.cannot_be_encrypted = True
         super().__init__(**kwargs)
 
     def open(self):

jrnl/FolderJournal.py

@@ -25,6 +25,7 @@ class Folder(Journal.Journal):
     def __init__(self, **kwargs):
         self.entries = []
         self._diff_entry_dates = []
+        self.cannot_be_encrypted = True
         super(Folder, self).__init__(**kwargs)
 
     def open(self):

jrnl/commands.py

@@ -13,6 +13,7 @@ avoid any possible overhead for these standalone commands.
 """
 import platform
 import sys
+from .exception import JrnlError
 
 
 def preconfig_diagnostic(_):
@@ -68,6 +69,13 @@ def postconfig_encrypt(args, config, original_config, **kwargs):
     # Open the journal
     journal = open_journal(args.journal_name, config)
 
+    if hasattr(journal, "cannot_be_encrypted") and journal.cannot_be_encrypted:
+        raise JrnlError(
+            "CannotEncryptJournalType",
+            journal_name=args.journal_name,
+            journal_type=journal.__class__.__name__,
+        )
+
     journal.config["encrypt"] = True
 
     new_journal = EncryptedJournal.from_journal(journal)

jrnl/exception.py

@@ -38,6 +38,13 @@ class JrnlError(Exception):
                 by at least {columns} in the configuration file or by using
                 --config-override at the command line
                 """,
+            "CannotEncryptJournalType": """
+                The journal {journal_name} can't be encrypted because it is a
+                {journal_type} journal.
+
+                To encrypt it, create a new journal referencing a file, export
+                this journal to the new journal, then encrypt the new journal.
+                """,
         }
 
         msg = error_messages[self.error_type].format(**kwargs)

tests/bdd/features/encrypt.feature

@@ -40,3 +40,12 @@ Feature: Encrypting and decrypting journals
         Then we should be prompted for a password
         And the output should contain "2013-06-10 15:40 Life is good"
 
+    Scenario Outline: Attempt to encrypt a folder or DayOne journal should result in an error
+        Given we use the config "<config_file>"
+        When we run "jrnl --encrypt"
+        Then the error output should contain "can't be encrypted"
+
+        Examples: configs
+        | config_file       |
+        | empty_folder.yaml |
+        | dayone.yaml       |