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Enable Lintables to be modified #1884

Merged
merged 17 commits into from
Feb 16, 2022
Merged

Enable Lintables to be modified #1884

merged 17 commits into from
Feb 16, 2022

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cognifloyd
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@cognifloyd cognifloyd commented Feb 13, 2022

We need a way to write files and keep track of how we've changed them.

This prepares for formatting in transforms in #1828. Feedback from that PR suggests that we'll need at least a count of the files that have changed and possibly a diff view that shows how files have changed.

This adds a setter for Lintable.content which monitors the content for changes..
When the content is changed, it sets Lintable.updated = True.
Original content is also preserved to facilitate further comparison or resetting the content if needed.

There is also a deleter for Lintable.content so that if something needs to modify a file externally, the developer can trigger reloading the content from disk with del lintable.content.

NB: I originally used a stream/file-like object because that's what ruamel.yaml's API expects. But that made the interface more confusing. The Transformer will have to create a StringIO instance on the fly when using ruamel.yaml.

Replaces #1865 (an alternative implementation)

@webknjaz
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Where are these streams closed? If they aren't, this will cause ResourceWarnings.

@cognifloyd
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The current implementation relies on StringIO so closing them is not an issue. If we need to switch to temporary files then we'd probably need to auto open/close them or something. I'm not sure where.

@lilatomic
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At least to me, it would be clearer to rename Lintable._content to original_content, and Lintable._writable to Lintable._content. That's the spirit of the comments next to them, and I think it would help remove confusion like "Why do we never update the content?". I would also in Lintable.__init__ assign both of them the value of content, I think that would eliminate a few null checks.

Could you also provide some guidance on when we would use content vs writable? That is, if I have a rule that can rewrite, would I always request a writable? or would I request the content, see if I need to change it, and then request the writable? I noticed that the tests seem to truncate the contents of the writable, I'm not sure if that's illustrative of the expected usage.

Could you also talk about why you went with a method to expose a writable stream, rather than a method to set the updated content? I understand why we're using streams over string; but why have def writable(self) -> TextIO rather than def update(self, contents: TextIO) -> None? I think an advantage of an update method is that it would allow for linters and lintables to better track their updates, eg with def update(self, contents: TextIO, linter_class: Type[AnsibleLintRule], comment: str = "") -> None. I think this would also simplify the usage of content vs writable, since a rule would always use content for the content and only invoke update if it needed to do that.

I'm excited about rules being able to remediate Ansible, and I think this lays important groundwork for that feature.

@cognifloyd cognifloyd changed the title Add Lintable.writable stream and Lintable.updated indicator Allow setting Lintable.content and add Lintable.updated indicator Feb 14, 2022
@cognifloyd
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OK. I changed the implementation from a Lintable.writable stream to a Lintable.content setter. I kept the same tests (modifying them to use Lintable.content instead of Lintable.writable).

@cognifloyd cognifloyd changed the title Allow setting Lintable.content and add Lintable.updated indicator Add Lintable.content setter and deleter + add Lintable.updated indicator Feb 14, 2022
@ssbarnea ssbarnea requested a review from webknjaz February 14, 2022 19:14
@webknjaz
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Why are the comments minimized?

@cognifloyd
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cognifloyd commented Feb 15, 2022

Why are the comments minimized?

Because they were about the old implementation. You asked about streams, for example, which this does not use any more. So I marked the comments as outdated.

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webknjaz commented Feb 15, 2022

I don't think we need to do this with legitimate comments. It's harder to find them this way. We mostly hide spam / outdated bot comments but doing this doesn't generate any notifications decreasing the chances of finding out what happened and why. So it's also bad for transparency. If the conversations need to be disregarded, just leave a comment about that — it's probably the best way to keep the discussions/decisions traceable.

Besides, GitHub already collapses big chunk of comments anyway. So when I open the thread to see the updates/answers to previous questions, it's rather confusing to see some approvals combined with "no reply" and "removed questions". Looks like this adds to the cognitive load of people trying to find own discussions that they started.

@cognifloyd
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okey dokey. unhid

@ssbarnea
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ssbarnea commented Feb 15, 2022

I do mark comments as outdated every-time they no longer apply to current implementation, just to keep the review size easy to read to other reviewers, including myself. The moment they become outdated, they become spam, and that is why github added these particular reasons when you hide them.

AFAIK, @webknjaz is the only one that was intrigued by this. Maybe it is time to check with others from the team and see what think.

I personally find long conversations hard to follow, hide option helps fighting that.

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Well, if there's disregarded comments without replies for no reason, it doesn't look good. I wasn't intrigued, I was only shocked by the disrespect. There is no indication informing me that everything has been updated and needs rechecking. The only indication is that there are some new commits without any context explaining that they contain different content. Anyway, I don't see why you disregard what I said — I merely described what signals I was getting and what I saw with my own eyes. I don't think you know better what I saw unless I explain, which I did.

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okey dokey. unhid

@cognifloyd thanks! For the future — it may be fine to hide things but then, take the responsibility of notifying the affected parties about this with an explicit comment and mentions that would trigger notifications and give people a chance to see what happened without forcing them to guess whether our judgment about their comments was reasonable. We can't always know upfront if what you thought another person meant is the same thing you perceived. Besides, we don't know/can't assume if the other party is caught up with the updates and making things disappear would inevitably cause extra cognitive load for those who care to understand how the context they may remember got transformed into a new one.

lintable = Lintable("bad_type.yaml", BASIC_PLAYBOOK)
assert lintable.content == BASIC_PLAYBOOK

with pytest.raises(TypeError):
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It is strongly recommended to always use the match= argument for all pytest.raises()/pytest.warns()/pytest.deprecated() uses to prevent accidental illegitimate passes.

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@cognifloyd cognifloyd Feb 15, 2022

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Doing that feels like relying on implementation details. Had I done that with the old implementation, I would have had to modify it with this implementation because the TypeError is now being raised in my code, but something else rose it with the old implementation. So, I don't like using the match= argument.

This test is not checking for a message. It is checking that it raises a TypeError for non-str things. I don't care why or what message is used, so adding a match= here is misleading about my intents when writing the code.

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Imagine you refactor that code and make a mistake in a function signature you call inside of the setter or down the stack. It will cause a TypeError and the test will still pass with a bug merged in 🤷‍♂️

Comment on lines +233 to +234
with lintable.path.open("w", encoding="utf-8") as f:
f.write(content)
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Why didn't you just do

Suggested change
with lintable.path.open("w", encoding="utf-8") as f:
f.write(content)
lintable.path.write_text(content)

?

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Reasoning is in #1884 (comment)

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I think that you are referring to the .resolve() call, which is something that is not happening here, no?

if not force and not self.updated:
# No changes to write.
return
with open(self.path.resolve(), mode="w", encoding="utf-8") as file:
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Why use an old-fashioned low-level API for this and not pathlib-native one?

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If a file is a symlink, I don't want to replace the symlink with an actual file, I want to update the contents of the symlink's target. I do not see pathlib methods for open or write that follow symlinks.

This matches the implementaiton introduced in #1770.

return self._content

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The use of a setter seems weird to me here. A natural goal of setters is to set values mostly but this one also does I/O and shuffles the internal state. It feels like this sort of thing would require an explicit method call.

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OTOH the whole idea of having a mutable object appears questionable — would it be possible to have some transformation API that would take one lintable and construct/return a new one in an immutable manner?

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The lintable instance is used all over the place. Making it immutable feels very odd. I would have to somehow make everything that accesses content via a Lintable check to see if something else has an in-memory change queued up to write to the file.

Feel free to open an alternative PR that shows how such an immutable object might work. I'm not willing to pursue that avenue.

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I'm open to an alternative to the setter, but I'm tired of reimplementing this. Show me what interface you want instead of a setter.

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You're right, it may be hard to make it immutable with the current codebase, I won't insist on refactoring the whole project, of course :)

Have you considered exposing a method? (just thinking out loud)

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@cidrblock Can you please help with this one?

@cidrblock cidrblock self-requested a review February 15, 2022 19:29
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Looks good.

The only comment I have, which is totally subjective and could go in this PR, in another PR or in the trash.......... and it's probably because I'm less familiar with the patterns in the repo.

I (personally) prefer to see all the class self.* attributes defined and typed at the top of the init, even without default values. I tend to look there first to see what something is when used later and it's type.... especially when I'm seeing code for the first time. Your call.

@cognifloyd
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The only comment I have, which is totally subjective and could go in this PR, in another PR [snip]

I (personally) prefer to see all the class self.* attributes defined and typed at the top of the init, even without default values.

I think that would be a fine follow-up PR. I'm trying to minimize the refactoring in this PR.

@ssbarnea
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As none of the current opened comments is critical, I will merge it as is. We can address these in follow-ups, especially as it is likely that we would need to tune the implementation while we start using it.

@ssbarnea ssbarnea merged commit 2a19a66 into ansible:main Feb 16, 2022
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Apparently some of the comments were not posted yesterday. Submitting them now.

Comment on lines +260 to +261
with open(self.path.resolve(), mode="w", encoding="utf-8") as file:
file.write(self._content or "")
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Oh, I didn't mean to suggest removing the resolution. I was thinking about something like

Suggested change
with open(self.path.resolve(), mode="w", encoding="utf-8") as file:
file.write(self._content or "")
self.path.resolve().write_text(self._content or "")

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Huh. I thought resolve() returned a string, not another Path object. Yeah, this would work.

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See #1913

Comment on lines +233 to +234
with lintable.path.open("w", encoding="utf-8") as f:
f.write(content)
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I think that you are referring to the .resolve() call, which is something that is not happening here, no?

lintable = Lintable("bad_type.yaml", BASIC_PLAYBOOK)
assert lintable.content == BASIC_PLAYBOOK

with pytest.raises(TypeError):
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Imagine you refactor that code and make a mistake in a function signature you call inside of the setter or down the stack. It will cause a TypeError and the test will still pass with a bug merged in 🤷‍♂️

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5 participants