Return zero exit-code when force-removing non-existing containers

[thaJeztah]

• replaces Container: let rm -f exit with success #821
• closes Container: let rm -f exit with success #821
• fixes docker rm --force should return 0 (zero) exit-code if container doesn't exist #2677
• fixes 'docker rm --force' to succeed when containers already deleted #2383

When using docker rm / docker container rm with the -f / --force option, attempts to remove non-existing containers should print a warning, but should return a zero exit code ("successful").

Currently, a non-zero exit code is returned, marking the removal as "failed";

$ docker rm -fv 798c9471b695
Error: No such container: 798c9471b695
$ echo $?
1

The command should match the behavior of rm / rm -f, with the exception that
a warning is printed (instead of silently ignored):

Running rm with -f silences output and returns a zero exit code:

touch some-file && rm -f no-such-file some-file; echo exit code: $?; ls -la
# exit code: 0
# total 0
# drwxr-xr-x    2 sebastiaan  staff    64 Aug 14 12:17 .
# drwxr-xr-x  199 sebastiaan  staff  6368 Aug 14 12:13 ..

mkdir some-directory && rm -rf no-such-directory some-directory; echo exit code: $?; ls -la
# exit code: 0
# total 0
# drwxr-xr-x    2 sebastiaan  staff    64 Aug 14 12:17 .
# drwxr-xr-x  199 sebastiaan  staff  6368 Aug 14 12:13 ..

Note that other reasons for a delete to fail should still result in a non-zero
exit code, matching the behavior of rm. For instance, in the example below,
the rm failed because directories can only be removed if the -r option is used;

touch some-file && mkdir some-directory && rm -f some-directory no-such-file some-file; echo exit code: $?; ls -la
# rm: some-directory: is a directory
# exit code: 1
# total 0
# drwxr-xr-x    3 sebastiaan  staff    96 Aug 14 14:15 .
# drwxr-xr-x  199 sebastiaan  staff  6368 Aug 14 12:13 ..
# drwxr-xr-x    2 sebastiaan  staff    64 Aug 14 14:15 some-directory

This patch updates the docker rm / docker container rm command to not produce
an error when attempting to remove a missing containers, and instead only print
the error, but return a zero (0) exit code.

With this patch applied:

docker create --name mycontainer busybox \
&& docker rm nosuchcontainer mycontainer; \
echo exit code: $?; \
docker ps -a --filter name=mycontainer
# df23cc8573f00e97d6e948b48d9ea7d75ce3b4faaab4fe1d3458d3bfa451f39d
# mycontainer
# Error: No such container: nosuchcontainer
# exit code: 0
# CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

Signed-off-by: Sebastiaan van Stijn github@gone.nl

- What I did

- How I did it

- How to verify it

- Description for the changelog

Fix `docker rm --force` returning a non-zero exit code if one or more containers did not exist

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

Merging #2678 into master will increase coverage by 0.25%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2678      +/-   ##
==========================================
+ Coverage   58.16%   58.42%   +0.25%     
==========================================
  Files         295      295              
  Lines       21207    21210       +3     
==========================================
+ Hits        12336    12391      +55     
+ Misses       7963     7909      -54     
- Partials      908      910       +2     

[thaJeztah]

@silvin-lubecki @cpuguy83 PTAL

[silvin-lubecki]

LGTM

[cpuguy83]

LGTM

Probably we should do this in the API, though.

[thaJeztah]

Probably we should do this in the API, though

hm, possibly; also feels a bit odd to have the API ignore a non-existing resource