Auto merge of #127946 - tgross35:fmt-builders-set-result, r=cuviper

bors · bors · commit a526d7ce45fd · 2024-07-27T02:26:30.000Z
Always set `result` during `finish()` in debug builders

Most functions for format builders set `self.result` after writing strings. This ensures that any further writing fails immediately rather than trying to write again.

A few `.finish()` methods and the `.finish_non_exhaustive` did have this same behavior, so update the remaining `.finish()` methods to make it consistent here.
diff --git a/library/core/src/fmt/builders.rs b/library/core/src/fmt/builders.rs
@@ -402,6 +402,7 @@ impl<'a, 'b: 'a> DebugTuple<'a, 'b> {
     }
 }
 
+/// A helper used to print list-like items with no special formatting.
 struct DebugInner<'a, 'b: 'a> {
     fmt: &'a mut fmt::Formatter<'b>,
     result: fmt::Result,
@@ -578,7 +579,8 @@ impl<'a, 'b: 'a> DebugSet<'a, 'b> {
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn finish(&mut self) -> fmt::Result {
-        self.inner.result.and_then(|_| self.inner.fmt.write_str("}"))
+        self.inner.result = self.inner.result.and_then(|_| self.inner.fmt.write_str("}"));
+        self.inner.result
     }
 }
 
@@ -721,7 +723,8 @@ impl<'a, 'b: 'a> DebugList<'a, 'b> {
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn finish(&mut self) -> fmt::Result {
-        self.inner.result.and_then(|_| self.inner.fmt.write_str("]"))
+        self.inner.result = self.inner.result.and_then(|_| self.inner.fmt.write_str("]"));
+        self.inner.result
     }
 }
 
@@ -1002,11 +1005,12 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
     pub fn finish(&mut self) -> fmt::Result {
-        self.result.and_then(|_| {
+        self.result = self.result.and_then(|_| {
             assert!(!self.has_key, "attempted to finish a map with a partial entry");
 
             self.fmt.write_str("}")
-        })
+        });
+        self.result
     }
 
     fn is_pretty(&self) -> bool {

Original file line number	Diff line number	Diff line change
`@@ -402,6 +402,7 @@ impl<'a, 'b: 'a> DebugTuple<'a, 'b> {`
`402`	`402`	`}`
`403`	`403`	`}`
`404`	`404`
	`405`	`+/// A helper used to print list-like items with no special formatting.`
`405`	`406`	`struct DebugInner<'a, 'b: 'a> {`
`406`	`407`	`fmt: &'a mut fmt::Formatter<'b>,`
`407`	`408`	`result: fmt::Result,`
`@@ -578,7 +579,8 @@ impl<'a, 'b: 'a> DebugSet<'a, 'b> {`
`578`	`579`	/// ```
`579`	`580`	`#[stable(feature = "debug_builders", since = "1.2.0")]`
`580`	`581`	`pub fn finish(&mut self) -> fmt::Result {`
`581`		`- self.inner.result.and_then(\|_\| self.inner.fmt.write_str("}"))`
	`582`	`+ self.inner.result = self.inner.result.and_then(\|_\| self.inner.fmt.write_str("}"));`
	`583`	`+ self.inner.result`
`582`	`584`	`}`
`583`	`585`	`}`
`584`	`586`
`@@ -721,7 +723,8 @@ impl<'a, 'b: 'a> DebugList<'a, 'b> {`
`721`	`723`	/// ```
`722`	`724`	`#[stable(feature = "debug_builders", since = "1.2.0")]`
`723`	`725`	`pub fn finish(&mut self) -> fmt::Result {`
`724`		`- self.inner.result.and_then(\|_\| self.inner.fmt.write_str("]"))`
	`726`	`+ self.inner.result = self.inner.result.and_then(\|_\| self.inner.fmt.write_str("]"));`
	`727`	`+ self.inner.result`
`725`	`728`	`}`
`726`	`729`	`}`
`727`	`730`
`@@ -1002,11 +1005,12 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {`
`1002`	`1005`	/// ```
`1003`	`1006`	`#[stable(feature = "debug_builders", since = "1.2.0")]`
`1004`	`1007`	`pub fn finish(&mut self) -> fmt::Result {`
`1005`		`- self.result.and_then(\|_\| {`
	`1008`	`+ self.result = self.result.and_then(\|_\| {`
`1006`	`1009`	`assert!(!self.has_key, "attempted to finish a map with a partial entry");`
`1007`	`1010`
`1008`	`1011`	`self.fmt.write_str("}")`
`1009`		`- })`
	`1012`	`+ });`
	`1013`	`+ self.result`
`1010`	`1014`	`}`
`1011`	`1015`
`1012`	`1016`	`fn is_pretty(&self) -> bool {`