🐛 delta 0.4.5 binary release messes up terminal on Ubuntu 20 04

[salmankhilji]

Release 0.4.5, when run on Ubuntu 20 04, messes up the terminal. After running delta, I see the diff output; however, any subsequent typing within the terminal is not echo'd back.

salman@byteevo-scm:~/Scratch$ ls update-pcs*
update-pcs  update-pcs-new
salman@byteevo-scm:~/Scratch$ ./delta -s update-pcs update-pcs-new 

comparing: update-pcs ⟶   update-pcs-new
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

│ 1  │#!/bin/sh                                                │ 1  │#!/bin/sh
│ 2  │for i in $(seq 3); do                                    │ 2  │for i in $(seq 4); do
│8m 3  │    rsync -av -e "ssh -i $HOME/.ssh/id_rsa" $HOME/.local→│ 3  │    rsync -av -e "ssh -i $HOME/.ssh/id_rsa" $HOME/.local→
│ 4  │    rsync -av -e "ssh -i $HOME/.ssh/id_rsa" $HOME/.local→│ 4  │    rsync -av -e "ssh -i $HOME/.ssh/id_rsa" $HOME/.local→
│ 5  │done                                                     │ 5  │done
salman@byteevo-scm:~/Scratch$ 
Command 'lll' not found, did you mean:

  command 'dll' from deb brickos (0.9.0.dfsg-12.2)
  command 'lld' from deb lld (1:10.0-50~exp1)
  command 'lli' from deb llvm-runtime (1:10.0-50~exp1)
  command 'llt' from deb storebackup (3.2.1-1+deb8u1build0.20.04.1)
  command 'llc' from deb llvm (1:10.0-50~exp1)

Try: sudo apt install <deb name>

salman@byteevo-scm:~/Scratch$ delta 0.4.5
salman@byteevo-scm:~/Scratch$ 

As you can see, I intentionally typed a non-existant command lll, which is not echo'd back. Then I typed ./delta --version, which is also not echo'd back. The result of the command is, however, seen in the output above.

[marcoieni]

I was able to reproduce it.
By the way with zsh it works.

[dandavison]

Hi @marcoieni. Do you understand what's happening here? I was not able to reproduce this in a docker container.

[marcoieni]

I tried with cargo install git-delta and I have the same problem. So it's not a problem of the released binary only.

I will patiently go back commit by commit to identify where the problem started :)

[dandavison]

Thanks very much @marcoieni! I'm on MacOS (and can run in Docker also) and cannot reproduce, but I will try to think what might be going wrong. Here are some questions in case they help pinpoint the problem

• Does it depend on the terminal emulator being used?
• Does the problem still occur with --paging=never?
• Does it occur with and without side-by-side?

[marcoieni]

• Does it depend on the terminal emulator being used?

Default ubuntu terminal emulator (gnome-terminal): works with zsh and doesn't work with bash.

• Does the problem still occur with --paging=never?

no!

• Does it occur with and without side-by-side?

yes, both cases

[dandavison]

Does the problem still occur with --paging=never?

no!

Interesting! What are your values of the DELTA_PAGER, BAT_PAGER, PAGER and LESS env vars?

[marcoieni]

they are empty

[marcoieni]

as you can see with paging=never it works. Otherwise it doesn't echo your input. I don't know why it added an 'l' at the end

[dandavison]

OK, if you could determine the first bad commit that would be fantastic.

[marcoieni]

It looks like the problem was introduced in 46eb84b

Also, the problem does not appear if diffs are displayed with a pager (less in my case).

Reproduction guide. Ubuntu 20.04, gnome terminal, bash:

git clone https://github.com/dandavison/delta
cd delta
# the following command will revert to last working state
git checkout a632e3f704d8e5b10326f6d79ad58807f2fa103d
cargo build --release
./target/release/delta file1 file2
# now if you try to type something you should be able to see what you type

# the following command will go to the point where the problem was introduced
git checkout 46eb84bd34f8ff67f749eec8a287d5a3e7a0919a
cargo build --release
./target/release/delta file1 file2
# now if you try to type something you should NOT be able to see what you type

@salmankhilji can you confirm my reprodution guide?

[dandavison]

Thanks @marcoieni, I think I can see that this is broken on MacOS, even though it isn't messing up my terminal: when I do
delta Cargo.toml /etc/passwd I do not see the full output (I only see the red removed lines from Cargo.toml). But when I do delta --paging=never Cargo.toml /etc/passwd I see the full output (removed and added lines).

I'm guessing I wrote some very bad process management code in 46eb84b and there's a race condition somewhere between delta, diff and less, resulting in some output being truncated.

[dandavison]

Thanks very much for debugging @marcoieni!

[marcoieni]

I am trying to find a solution as well, I don't get why it doesn't work <.<

[marcoieni]

the problem is that you don't have to pass the writer variable to that function.

I am trying to solve the problem against master and doing a PR.

The problem is: that variable is required by tests