diff: ERROR: unexpected error - 'not in cache'

[josecelano]

Description

When I tried to compare two commits I get an error.

The command is: dvc diff f0c0269 16ba2cd
I'm using your sample repo: https://github.com/iterative/example-get-started

Reproduce

Command 1 (compare commit with previous "dvc add" commit):

dvc diff f0c0269 16ba2cd

Output:

ERROR: unexpected error - 'not in cache'                              

Having any troubles? Hit us up at https://dvc.org/support, we are always happy to help!

Command 2 (compare commit with a commit before "dvc add" commit):

dvc diff 3e07290 16ba2cd

Output:

Added:                                                                
    data/data.xml

files summary: 1 added

How to reproduce it:

git clone https://github.com/iterative/example-get-started
cd example-get-started/
dvc diff 16ba2cd f0c0269

Expected

These are the first commits in your sample repo:

* 08a3b89 - (tag: 4-import-data) Import raw data (overwrite) (2021-05-20 23:56:52 -0400) <Olivaw Owlet>
* 16ba2cd - (tag: 3-config-remote) Configure default remote (2021-05-19 20:10:12 -0400) <Olivaw Owlet>
* f0c0269 - (tag: 2-track-data) Add raw data (2021-05-18 16:23:32 -0400) <Olivaw Owlet>
* 3e07290 - (tag: 1-dvc-init) Initialize DVC project (2021-05-17 12:36:52 -0400) <Olivaw Owlet>
* 90b2aea - (tag: 0-git-init) Initialize Git repository (2021-05-16 08:50:12 -0400) <Olivaw Owlet>

If you show changes on the third commit f0c0269 with git show f0c0269 you can see:

commit f0c026993d3dc8aa4d79426acb59b81dbb63e5a2 (tag: 2-track-data)
Author: Olivaw Owlet <64868532+iterative-olivaw@users.noreply.github.com>
Date:   Tue May 18 16:23:32 2021 -0400

    Add raw data

diff --git a/data/.gitignore b/data/.gitignore
new file mode 100644
index 0000000..fc12be5
--- /dev/null
+++ b/data/.gitignore
@@ -0,0 +1 @@
+/data.xml
diff --git a/data/data.xml.dvc b/data/data.xml.dvc
new file mode 100644
index 0000000..8fab3a9
--- /dev/null
+++ b/data/data.xml.dvc
@@ -0,0 +1,5 @@
+outs:
+- md5: a304afb96060aad90176268345e10355
+  size: 37891850
+  path: data.xml
+  desc: Initial XML StackOverflow dataset (raw data)

I suppose that means that was the commit where the file data\data.xml was added using dvc.

What I expect:

If I create a commit adding a file with dvc add and I compare the next commit with the previous one I expect the dvc diff two show that the file was added.

That means I expect the command 1 to have to same output as command 2 because the file was added in the commit f0c0269

Environment information

Output of `dvc diff -v f0c0269 16ba2cd:

2021-09-30 17:03:09,704 ERROR: unexpected error - 'not in cache'      
------------------------------------------------------------
Traceback (most recent call last):
  File "/home/josecelano/anaconda3/lib/python3.8/site-packages/dvc/main.py", line 55, in main
    ret = cmd.do_run()
  File "/home/josecelano/anaconda3/lib/python3.8/site-packages/dvc/command/base.py", line 45, in do_run
    return self.run()
  File "/home/josecelano/anaconda3/lib/python3.8/site-packages/dvc/command/diff.py", line 131, in run
    del diff["not in cache"]
KeyError: 'not in cache'
------------------------------------------------------------
2021-09-30 17:03:09,891 DEBUG: Version info for developers:
DVC version: 2.7.3 (pip)
---------------------------------
Platform: Python 3.8.8 on Linux-5.10.0-1045-oem-x86_64-with-glibc2.10
Supports:
	azure (adlfs = 2021.9.1, knack = 0.8.2, azure-identity = 1.6.1),
	http (aiohttp = 3.7.4.post0, aiohttp-retry = 2.4.5),
	https (aiohttp = 3.7.4.post0, aiohttp-retry = 2.4.5)
Cache types: <https://error.dvc.org/no-dvc-cache>
Caches: local
Remotes: https
Workspace directory: ext4 on /dev/mapper/vgubuntu-root
Repo: dvc, git

Having any troubles? Hit us up at https://dvc.org/support, we are always happy to help!
2021-09-30 17:03:09,892 DEBUG: Analytics is enabled.
2021-09-30 17:03:09,926 DEBUG: Trying to spawn '['daemon', '-q', 'analytics', '/tmp/tmpx7a6ek24']'
2021-09-30 17:03:09,927 DEBUG: Spawned '['daemon', '-q', 'analytics', '/tmp/tmpx7a6ek24']'

[efiop]

@josecelano Thanks for a great description! 🙏

For the record: if not resolved earlier, will likely get solved by #6594

[josecelano]

OK thank you @efiop for your fast reply. It seems this kind of references do not work either:

dvc diff refs/remotes/origin/main^ other-branch

I'm trying to apply a "hack" to get the previous commit.

[dberenbaum]

That means I expect the command 1 to have to same output as command 2 because the file was added in the commit f0c0269

Since the data.xml.dvc exists in f0c0269 but not in 3e07290, these shouldn't have the same output, right @josecelano? I would expect dvc diff f0c0269 16ba2cd to return nothing. I think nautilus-cyberneering/chinese-ideographs#38 sums it up: dvc diff fails when no files have been changed.

For example:

$ dvc diff 16ba2cd 08a3b89
2022-02-17 13:51:57,963 ERROR: unexpected error - 'not in cache'
------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/dave/Code/dvc/dvc/cli/__init__.py", line 78, in main
    ret = cmd.do_run()
  File "/Users/dave/Code/dvc/dvc/cli/command.py", line 22, in do_run
    return self.run()
  File "/Users/dave/Code/dvc/dvc/commands/diff.py", line 131, in run
    del diff["not in cache"]
KeyError: 'not in cache'
------------------------------------------------------------

@efiop The error isn't related to #6594 or dvc/repo/diff.py.

dvc/dvc/commands/diff.py

Line 131 in 0b18efb

del diff["not in cache"]

This line simply doesn't handle the case where that key doesn't exist. Do you want me to submit a PR?

[josecelano]

dvc diff f0c0269 16ba2cd

hi @dberenbaum . I think there are 2 problems:

1. The one related to this issue: missing changes in diff result.
2. The one related to that issue you mentioned: 'not in cache' return an error exit code.

Missing changes in diff result

I do not expect dvc diff f0c0269 16ba2cd to return nothing because the data was added on f0c0269.

* 16ba2cd - (tag: 3-config-remote) Configure default remote (2021-05-19 20:10:12 -0400) <Olivaw Owlet>
* f0c0269 - (tag: 2-track-data) Add raw data (2021-05-18 16:23:32 -0400) <Olivaw Owlet>

And be aware that dvc diff 3e07290 16ba2cd and dvc diff 3e07290 16ba2cd do not have the same output:

dvc diff 3e07290 16ba2cd
Added:                                                                
    data/data.xml

files summary: 1 added

dvc diff 16ba2cd 3e07290
Deleted:                                                              
    data/data.xml

files summary: 1 deleted

But maybe my expectation was wrong. I suppose the dvd diff should have similar behaviour to git diff and in this case:

git diff --name-only f0c0269 16ba2cd
.dvc/config

In the first case, the diff does not contain any dvc pointer.

git diff --name-only 3e07290 16ba2cd
.dvc/config
data/.gitignore
data/data.xml.dvc

In the second diff we have the data/data.xml.dvc.

So basically, I think I was wrong and we can close this issue. The data was added in commit f0c0269, so there are no changes with the next commit 16ba2cd. There are only changes if you compare it with the previous one 3e07290 where there was no data.

I'm sorry for wasting your time.

'not in cache' return an error exit code

Regarding the second point, if you execute:

dvc diff f0c0269 16ba2cd
ERROR: unexpected error - 'not in cache'                              

Having any troubles? Hit us up at https://dvc.org/support, we are always happy to help!

The exit code is 255:

echo $?
255

I do not know why that's considered an error. Besides, I do not know why that error is shown in this case. Shouldn't the DVD diff command give you only the changes in the git repo whiteout checking the state of the cache?

Anyway, that is a different topic. It could be a new issue if more people agree that at least it should not return an error code.

cc @yeraydavidrodriguez

[dberenbaum]

I do not know why that's considered an error. Besides, I do not know why that error is shown in this case. Shouldn't the DVD diff command give you only the changes in the git repo whiteout checking the state of the cache?

It should not return an error. It should return empty output and a 0 exit code.

By default, dvc diff will compare the current workspace to the last commit and show files missing from the cache unless you pass --hide-missing. When comparing two revisions, --hide-missing is implied, and this "not in cache" info is deleted since it's irrelevant. The error you see is a bug that arises because DVC is trying to delete this "not in cache" info when no such info exists to delete.