Implement DebugStruct::non_exhaustive.
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r? @kennytm (rust_highfive has picked a reviewer for you, use r? to override) |
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r? @scottmcm since they saw the internals post. |
CAD97
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Nov 24, 2019
src/libcore/fmt/builders.rs
Outdated
| /// # #![feature(debug_non_exhaustive)] | ||
| /// use std::fmt; | ||
| /// | ||
| /// struct Foo; |
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I'd add a field foo to this structure, just for clarity's sake.
Probably Box<dyn (pick your favorite object safe trait that isn't `Debug`)>.
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Would it be simpler to print e.g. smth like pub fn non_exhaustive(&mut self) -> &mut DebugStruct<'a, 'b> {
self.result = self.result.and_then(|_| {
if self.is_pretty() {
if !self.has_fields {
self.fmt.write_str(" {\n")?;
}
let mut slot = None;
let mut state = Default::default();
let mut writer = PadAdapter::wrap(&mut self.fmt, &mut slot, &mut state);
writer.write_str("..\n")
} else {
let prefix = if self.has_fields { ", " } else { " { " };
self.fmt.write_str(prefix)?;
self.fmt.write_str("..")
}
});
self.has_fields = true;
self
}
pub fn finish_non_exhaustive(&mut self) -> fmt::Result {
self.non_exhaustive().finish()
} |
That is certainly another possibility, I'd be interested to hear other people's opinions. |
CAD97
reviewed
Nov 24, 2019
src/libcore/fmt/builders.rs
Outdated
| @@ -190,7 +195,7 @@ impl<'a, 'b: 'a> DebugStruct<'a, 'b> { | |||
| /// } | |||
| /// | |||
| /// assert_eq!( | |||
| /// format!("{:?}", Foo), | |||
| /// format!("{:?}", Foo { foo: Box::new([1, 2].into_iter().copied()) }), | |||
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🚩🚩🚩🚩🚩🚩
You do not want to use .into_iter().copied() here. This takes an autoref to &[_] and will break when we eventually add impl IntoIterator for [_]. Use .iter() instead.
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Ping from triage: @scottmcm - all checks pass, can you please review this PR? |
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Pinging again from triage: |
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r? @dtolnay |
dtolnay
reviewed
Dec 15, 2019
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Thanks! I would be on board with supporting .. in DebugStruct.
-
I think opaque_field should be removed from this PR. It is easy enough to get the same behavior with
field("field", &format_args!("_")). But the representationStruct { field: _ }is not one that I find intuitive or would want to encourage. Almost anything would be better, for examplefield("field", &format_args!("<some Iterator>")). I would prefer to leave this up to the caller rather than dictating a default representation for opaque fields. This way the caller can write an impl that is as useful as possible within their constraints. -
The bool argument of non_exhaustive doesn't seem useful. The caller would pretty much always need to pass true which is just noisy. In the rare case that a struct may or may not print as nonexhaustive depending on a runtime decision, the Debug impl can use an
ifaround the non_exhaustive call. -
I would lean toward making this an alternative to
finishto sidestep the ambiguity about what it should do if you print more fields after calling non_exhaustive.f.debug_struct("Struct").field("field", &self.field).finish_non_exhaustive()
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
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Thanks @derekdreery! This looks good to me. Could you please file a tracking issue and put the issue number into the #[unstable(...)] attribute in the PR? After that I'm happy to merge this. |
richard-uk1
changed the title
DebugStruct::non_exhaustive and DebugStruct::opaque_field.DebugStruct::non_exhaustive.
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Tracking issue added :) |
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Could you also squash the commits down into just one? Thanks! It would also be good to update the PR description to be slightly more commit-y -- e.g., removing open questions, etc. -- since it'll go into the bors merge commit, so is preserved for all history. This is more of a personal pet peeve of mine though :) |
Off topic question: bors-ng has a setting where you can ignore any part of the PR description after some special line, which I often set to e.g. Is this something that the rust-lang bors is capable of doing? If not, should we add it? If so, should we enable it and teach people to use it? |
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Done and done. |
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📌 Commit 985127c has been approved by |
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🌲 The tree is currently closed for pull requests below priority 100, this pull request will be tested once the tree is reopened |
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…=dtolnay
Implement `DebugStruct::non_exhaustive`.
This patch adds a function (finish_non_exhaustive) to add ellipsis before the closing brace when formatting using `DebugStruct`.
## Example
```rust
#![feature(debug_non_exhaustive)]
use std::fmt;
struct Bar {
bar: i32,
hidden: f32,
}
impl fmt::Debug for Bar {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("Bar")
.field("bar", &self.bar)
.non_exhaustive(true) // Show that some other field(s) exist.
.finish()
}
}
assert_eq!(
format!("{:?}", Bar { bar: 10, hidden: 1.0 }),
"Bar { bar: 10, .. }",
);
```
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💔 Test failed - checks-azure |
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☔ The latest upstream changes (presumably #67540) made this pull request unmergeable. Please resolve the merge conflicts. |
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This needs a rebase but is otherwise ready to land. |
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Should be up-to-date now. |
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
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https://dev.azure.com/rust-lang/e71b0ddf-dd27-435a-873c-e30f86eea377/_apis/build/builds/18417/logs/66 looks like it wants a rustfmt of these files. |
kennytm
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ready for review |
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Thanks! @bors r+ |
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📌 Commit 73124df has been approved by |
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Implement `DebugStruct::non_exhaustive`.
This patch adds a function (finish_non_exhaustive) to add ellipsis before the closing brace when formatting using `DebugStruct`.
## Example
```rust
#![feature(debug_non_exhaustive)]
use std::fmt;
struct Bar {
bar: i32,
hidden: f32,
}
impl fmt::Debug for Bar {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("Bar")
.field("bar", &self.bar)
.non_exhaustive(true) // Show that some other field(s) exist.
.finish()
}
}
assert_eq!(
format!("{:?}", Bar { bar: 10, hidden: 1.0 }),
"Bar { bar: 10, .. }",
);
```
|
☀️ Test successful - checks-azure |
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This patch adds a function (finish_non_exhaustive) to add ellipsis before the closing brace when formatting using
DebugStruct.Example