From 13fc6a9b6ad4f0ee0a783c91825ab7ad35dd2b64 Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@joeyh.name>
Date: Thu, 9 Jun 2022 14:24:56 -0400
Subject: [PATCH] fix to use 1 chunk for empty file

Fix retrival of an empty file that is stored in a special remote with
chunking enabled.

The speculative chunk stuff caused a reversion by adding an empty list for
the empty file. Which is just wrong; the empty file is still stored on the
remote, and should be retrieved like any other file. It uses 1 chunk, so
`max 1` is the simple fix.

Sponsored-by: Noam Kremen on Patreon
---
 CHANGELOG                                       |  3 +++
 Remote/Helper/Chunked.hs                        |  2 +-
 ...n_file_size_0_from_external_spec_remote.mdwn |  2 ++
 ..._2_1d78459554bc12d0423a317bd9f466d1._comment | 17 +++++++++++++++++
 4 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 doc/bugs/error_out_on_file_size_0_from_external_spec_remote/comment_2_1d78459554bc12d0423a317bd9f466d1._comment

diff --git a/CHANGELOG b/CHANGELOG
index ae14d55acd..24b3c6cb5b 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -6,6 +6,9 @@ git-annex (10.20220526) UNRELEASED; urgency=medium
     The location value no longer needs to match the url of an existing
     git remote, and locations not using ssh:// will work now, including
     both paths and host:/path
+  * Fix retrival of an empty file that is stored in a special remote with 
+    chunking enabled.
+    (Fixes a reversion in 8.20201103)
 
  -- Joey Hess <id@joeyh.name>  Wed, 01 Jun 2022 13:23:05 -0400
 
diff --git a/Remote/Helper/Chunked.hs b/Remote/Helper/Chunked.hs
index a8d928c597..72e33fe77e 100644
--- a/Remote/Helper/Chunked.hs
+++ b/Remote/Helper/Chunked.hs
@@ -554,7 +554,7 @@ chunkKeys' onlychunks u chunkconfig k = do
 			Nothing -> l
 			Just keysz -> 
 				let (d, m) = keysz `divMod` fromIntegral chunksz
-				    chunkcount = d + if m == 0 then 0 else 1
+				    chunkcount = max 1 (d + if m == 0 then 0 else 1)
  				    v = (FixedSizeChunks chunksz, chunkcount)
 				in if v `elem` recorded
 					then l
diff --git a/doc/bugs/error_out_on_file_size_0_from_external_spec_remote.mdwn b/doc/bugs/error_out_on_file_size_0_from_external_spec_remote.mdwn
index b2358f32a3..a2ad892628 100644
--- a/doc/bugs/error_out_on_file_size_0_from_external_spec_remote.mdwn
+++ b/doc/bugs/error_out_on_file_size_0_from_external_spec_remote.mdwn
@@ -86,3 +86,5 @@ so I do not think it is an issue of the remote (which might also have some size
 
 
 tried both 8.20211123 and  10.20220504 from debian 
+
+> [[fixed|done]] --[[Joey]]
diff --git a/doc/bugs/error_out_on_file_size_0_from_external_spec_remote/comment_2_1d78459554bc12d0423a317bd9f466d1._comment b/doc/bugs/error_out_on_file_size_0_from_external_spec_remote/comment_2_1d78459554bc12d0423a317bd9f466d1._comment
new file mode 100644
index 0000000000..a37c6f1d06
--- /dev/null
+++ b/doc/bugs/error_out_on_file_size_0_from_external_spec_remote/comment_2_1d78459554bc12d0423a317bd9f466d1._comment
@@ -0,0 +1,17 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 2"""
+ date="2022-06-09T18:05:15Z"
+ content="""
+This was broken by [[!commit dad4be97c2057db1ef3a13bb983d1701a90c9069]].
+
+For a key of size zero, `addspeculative` adds on a `[]` to the list of chunk
+key. But that causes retrieveChunks to think that it's already retrieved
+all the chunks, so it avoids doing any retrieval, so the file is not
+written. It needs to retrieve the empty key even though it's empty,
+so it can decrypt it when it's encrypted; git-annex does not special case
+empty file retrieval.
+
+Odd that testremote did not detect this. It does test with empty keys, and
+with chunking.
+"""]]