From 1f356d66a694ba5fe68d7b38ab59fc16e6233d5a Mon Sep 17 00:00:00 2001
From: David Logie <djl@mksh.org>
Date: Fri, 25 Jan 2019 14:06:30 +0000
Subject: [PATCH] First attempt at fixing #3132.

Add a new `no_clobber` config option that contains a list of
"miscellaneous" metadata fields not to be overwritten by empty values.

I'm not entirely happy with the `no_clobber` name. Suggestions welcome.
---
 beets/autotag/__init__.py |  9 +++++++--
 beets/config_default.yaml | 13 +++++++++++++
 docs/changelog.rst        |  3 +++
 docs/reference/config.rst | 25 +++++++++++++++++++++++++
 4 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/beets/autotag/__init__.py b/beets/autotag/__init__.py
index 90d294c61..6783929cd 100644
--- a/beets/autotag/__init__.py
+++ b/beets/autotag/__init__.py
@@ -154,9 +154,14 @@ def apply_metadata(album_info, mapping):
                       'albumdisambig',
                       'releasegroupdisambig',
                       'data_source',):
+            # Don't overwrite fields with empty values unless the
+            # field is explicitly allowed to be overwritten
+            clobber = field not in config['no_clobber'].get()
             value = getattr(album_info, field)
-            if value is not None:
-                item[field] = value
+            if value is None and not clobber:
+                continue
+            item[field] = value
+
         if track_info.disctitle is not None:
             item.disctitle = track_info.disctitle
 
diff --git a/beets/config_default.yaml b/beets/config_default.yaml
index 26babde55..0e6e01efa 100644
--- a/beets/config_default.yaml
+++ b/beets/config_default.yaml
@@ -30,6 +30,19 @@ import:
     bell: no
     set_fields: {}
 
+no_clobber:
+  - albumtype
+  - label
+  - asin
+  - catalognum
+  - script
+  - language
+  - country
+  - albumstatus
+  - albumdisambig
+  - releasegroupdisambig
+  - data_source
+
 clutter: ["Thumbs.DB", ".DS_Store"]
 ignore: [".*", "*~", "System Volume Information", "lost+found"]
 ignore_hidden: yes
diff --git a/docs/changelog.rst b/docs/changelog.rst
index b896604c2..746a3f5be 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -63,6 +63,9 @@ New features:
   provider: you can match tracks and albums using the Spotify database.
   Thanks to :user:`rhlahuja`.
   :bug:`3123`
+* A new ``no_clobber`` configuration option allows setting a list of
+  fields not to be overwritten by empty values upon re-importing items.
+  :bug:`3132`
 
 
 Changes:
diff --git a/docs/reference/config.rst b/docs/reference/config.rst
index 57cb6c295..44f7dd576 100644
--- a/docs/reference/config.rst
+++ b/docs/reference/config.rst
@@ -303,6 +303,31 @@ The defaults look like this::
 
 See :ref:`aunique` for more details.
 
+
+.. _no_clobber:
+
+no_clobber
+~~~~~~~~~~
+
+A list of fields that should not be overwritten by empty values when
+re-importing items.
+
+The default is::
+
+    no_clobber:
+      - albumtype
+      - label
+      - asin
+      - catalognum
+      - script
+      - language
+      - country
+      - albumstatus
+      - albumdisambig
+      - releasegroupdisambig
+      - data_source
+
+
 .. _terminal_encoding:
 
 terminal_encoding