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feat: add ability to show unified diffs for changed files #562

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@dstanek dstanek commented Feb 8, 2022

Signed-off-by: David Stanek dstanek@dstanek.com

The now() template builtin is being used in the test and is an alias
for datetime.utcnow(). The now however, just uses datetime.now(). This
means that my datetime.now() will always make this test fail.

Signed-off-by: David Stanek <dstanek@dstanek.com>
Signed-off-by: David Stanek <dstanek@dstanek.com>
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dstanek commented Feb 8, 2022

I'm still working on this, but I wanted to get the idea out there.

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the tricky part are updates, they apply some diff without asking.

(apply_cmd << diff)(retcode=None)

Gotta do something about that, but anyways that's already a problem, so this won't make it worse.

some code comments too.

very nice addition, thanks!

copier/tools.py Outdated
elif line.startswith("-"):
color_print(colorama.Fore.RED, f"{indent}{line}")
elif line.startswith("+"):
color_print(colorama.Fore.GREEN, f"{indent}{line}")
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So I was going down this path first, but it seemed very difficult to get the result I wanted. I went ahead and finished that work a put together a gist showing the differences. orig.diff is the code from this PR and new.diff uses pygments and prompt_toolkit.

One reason the new code is much larger is that I wanted to have the two-line file header yellow like it is with git. This meant that I had to extend the lexer. In order to add the extra indentation, I had to also extend the PygmentsTokens class to inject whitespace. There may be better ways to accomplish these tasks, but I'm never had to dip into the bowels of these libraries before.

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I see.

Well, I'll have to do local testing for both implementations, because code looks complex in both cases, so if we're getting a complexity, I'll get the one that looks/works better 😄

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I'll update this implementation here since that's what I'm actively using and I think I can make it cleaner and more concise. If you like the other way better I can switch to that later.

copier/tools.py Outdated


def color_print(color: int, msg: str):
print(f"{color}{msg}{colorama.Fore.RESET}")
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@@ -144,6 +151,7 @@ class Worker:
overwrite: bool = False
pretend: bool = False
quiet: bool = False
diff: bool = False
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This is a nice addition. I don't think it's needed to add a new flag for it.

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Just default to always diff when we can?

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Yes, I can't imagine a use case where the no diff is more useful if we're on interactive mode.

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codecov-commenter commented Feb 8, 2022

Codecov Report

Merging #562 (57897f6) into master (e4eccc2) will decrease coverage by 0.97%.
The diff coverage is 31.70%.

Impacted file tree graph

@@            Coverage Diff             @@
##           master     #562      +/-   ##
==========================================
- Coverage   96.29%   95.32%   -0.98%     
==========================================
  Files          41       41              
  Lines        2701     2737      +36     
==========================================
+ Hits         2601     2609       +8     
- Misses        100      128      +28     
Flag Coverage Δ
unittests 95.32% <31.70%> (-0.98%) ⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files Coverage Δ
copier/tools.py 73.45% <20.00%> (-19.41%) ⬇️
copier/main.py 92.74% <55.55%> (-1.15%) ⬇️
copier/cli.py 96.51% <100.00%> (+0.04%) ⬆️
tests/test_templated_prompt.py 100.00% <100.00%> (ø)

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e4eccc2...57897f6. Read the comment docs.

copier/tools.py Outdated
Comment on lines 196 to 209
try:
original_lines = get_lines(original_content)
except Exception:
color_print(
colorama.Fore.YELLOW, "diff unavailable: unable to determine encoding"
)
return
try:
new_lines = get_lines(new_content)
except Exception:
color_print(
colorama.Fore.YELLOW, "diff unavailable: unable to determine encoding"
)
return
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I know some flake8 plugins would say: "only one line in a try block", but this could probably be factorized as:

Suggested change
try:
original_lines = get_lines(original_content)
except Exception:
color_print(
colorama.Fore.YELLOW, "diff unavailable: unable to determine encoding"
)
return
try:
new_lines = get_lines(new_content)
except Exception:
color_print(
colorama.Fore.YELLOW, "diff unavailable: unable to determine encoding"
)
return
try:
original_lines = get_lines(original_content)
new_lines = get_lines(new_content)
except Exception:
color_print(
colorama.Fore.YELLOW, "diff unavailable: unable to determine encoding"
)
return

Also, is there a reason you catch Exception rather than the more specific UnicodeDecodeError?

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@dstanek dstanek Feb 9, 2022

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I could combine the try blocks.

The reason I'm currently catching Exception is mostly because this isn't ready to merge. My first version used chardet and there were some exceptions to catch, then I decided to do a "detect on the cheap" algorithm to avoid an extra dependency and finally settled on hard coding utf-8 once I realized that Jinja is already doing that. If the final version is just the single decode then I could switch to catch that one exception.

Since the previous implementations had a few exceptions to catch and there is no particular handing for any of them I just went with Exception.

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I see, thanks!

@yajo yajo mentioned this pull request Mar 28, 2022
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yajo commented Mar 28, 2022

Hi folks! This was stiill under my radar, although quite deferred because it needs some testing and deep analyzing.

However, recently we got #627 which proposes to remove --overwrite and instead let the user solve the diff after updating. IMHO that seems a simpler approach, both in code and in behavior.

I'd love to hear your opinions.

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dstanek commented Apr 8, 2022

Hi folks! This was stiill under my radar, although quite deferred because it needs some testing and deep analyzing.

However, recently we got #627 which proposes to remove --overwrite and instead let the user solve the diff after updating. IMHO that seems a simpler approach, both in code and in behavior.

I'd love to hear your opinions.

I'll take a look at that in more detail, but it doesn't seem related to this PR. In this PR I wanted the ability do what Ansible calls "check mode." The ability to run a command and see what would change if it were to be applied.

Just a little background on my use case. I have a set of a few dozen microservices (likely to keep growing) that are based on the same configuration files and general structure. I want to convert it to use copier as the base for management. New services would use copier to start off. With this feature, we could make changes to our base configuration repo (say a logging format change) and have an easy way for a service owner to see what is different without creating new files. We could also run this over all services to see which is out of sync (run a weekly report from CICD like dependabot).

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4 participants