From 985127ce8fe6ec1351768224579ccc566689ff39 Mon Sep 17 00:00:00 2001 From: Richard Dodd Date: Sun, 24 Nov 2019 20:44:19 +0000 Subject: [PATCH] Implement `finish_non_exhaustive` for `DebugStruct`. --- src/libcore/fmt/builders.rs | 69 ++++++++++++++++++++++--- src/libcore/tests/fmt/builders.rs | 83 +++++++++++++++++++++++++++++++ src/libcore/tests/lib.rs | 1 + 3 files changed, 147 insertions(+), 6 deletions(-) diff --git a/src/libcore/fmt/builders.rs b/src/libcore/fmt/builders.rs index e6e3454b36f81..dcdd26634de46 100644 --- a/src/libcore/fmt/builders.rs +++ b/src/libcore/fmt/builders.rs @@ -165,6 +165,62 @@ impl<'a, 'b: 'a> DebugStruct<'a, 'b> { self } + /// Marks the struct as non-exhaustive, indicating to the reader that there are some other + /// fields that are not shown in the debug representation. + /// + /// # Examples + /// + /// ``` + /// # #![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) + /// .finish_non_exhaustive() // Show that some other field(s) exist. + /// } + /// } + /// + /// assert_eq!( + /// format!("{:?}", Bar { bar: 10, hidden: 1.0 }), + /// "Bar { bar: 10, .. }", + /// ); + /// ``` + #[unstable(feature = "debug_non_exhaustive", issue = "67364")] + pub fn finish_non_exhaustive(&mut self) -> fmt::Result { + self.result = self.result.and_then(|_| { + // Draw non-exhaustive dots (`..`), and open brace if necessary (no fields). + 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 { + if self.has_fields { + self.fmt.write_str(", ..")?; + } else { + self.fmt.write_str(" { ..")?; + } + } + if self.is_pretty() { + self.fmt.write_str("}")? + } else { + self.fmt.write_str(" }")?; + } + Ok(()) + }); + self.result + } + /// Finishes output and returns any error encountered. /// /// # Examples @@ -194,15 +250,16 @@ impl<'a, 'b: 'a> DebugStruct<'a, 'b> { /// ``` #[stable(feature = "debug_builders", since = "1.2.0")] pub fn finish(&mut self) -> fmt::Result { - if self.has_fields { - self.result = self.result.and_then(|_| { + self.result = self.result.and_then(|_| { + if self.has_fields { if self.is_pretty() { - self.fmt.write_str("}") + self.fmt.write_str("}")? } else { - self.fmt.write_str(" }") + self.fmt.write_str(" }")?; } - }); - } + } + Ok(()) + }); self.result } diff --git a/src/libcore/tests/fmt/builders.rs b/src/libcore/tests/fmt/builders.rs index 255724432816d..8f426abe43ffa 100644 --- a/src/libcore/tests/fmt/builders.rs +++ b/src/libcore/tests/fmt/builders.rs @@ -93,6 +93,89 @@ mod debug_struct { }", format!("{:#?}", Bar)); } + + #[test] + fn test_only_non_exhaustive() { + struct Foo; + + impl fmt::Debug for Foo { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt.debug_struct("Foo") + .finish_non_exhaustive() + } + } + + + assert_eq!("Foo { .. }", format!("{:?}", Foo)); + assert_eq!( +"Foo { + .. +}", + format!("{:#?}", Foo)); + } + + #[test] + fn test_multiple_and_non_exhaustive() { + struct Foo; + + impl fmt::Debug for Foo { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt.debug_struct("Foo") + .field("bar", &true) + .field("baz", &format_args!("{}/{}", 10, 20)) + .finish_non_exhaustive() + } + } + + assert_eq!("Foo { bar: true, baz: 10/20, .. }", format!("{:?}", Foo)); + assert_eq!( +"Foo { + bar: true, + baz: 10/20, + .. +}", + format!("{:#?}", Foo)); + } + + #[test] + fn test_nested_non_exhaustive() { + struct Foo; + + impl fmt::Debug for Foo { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt.debug_struct("Foo") + .field("bar", &true) + .field("baz", &format_args!("{}/{}", 10, 20)) + .finish_non_exhaustive() + } + } + + struct Bar; + + impl fmt::Debug for Bar { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt.debug_struct("Bar") + .field("foo", &Foo) + .field("hello", &"world") + .finish_non_exhaustive() + } + } + + assert_eq!("Bar { foo: Foo { bar: true, baz: 10/20, .. }, hello: \"world\", .. }", + format!("{:?}", Bar)); + assert_eq!( +"Bar { + foo: Foo { + bar: true, + baz: 10/20, + .. + }, + hello: \"world\", + .. +}", + format!("{:#?}", Bar)); + } + } mod debug_tuple { diff --git a/src/libcore/tests/lib.rs b/src/libcore/tests/lib.rs index b28ed2eaa0876..904c37fe54255 100644 --- a/src/libcore/tests/lib.rs +++ b/src/libcore/tests/lib.rs @@ -5,6 +5,7 @@ #![feature(core_private_bignum)] #![feature(core_private_diy_float)] #![feature(debug_map_key_value)] +#![feature(debug_non_exhaustive)] #![feature(dec2flt)] #![feature(exact_size_is_empty)] #![feature(fixed_size_array)]