Improve docs for single_line_if_else_max_width & add tests

Configurations.md

@@ -2381,12 +2381,62 @@ Don't reformat out of line modules
 
 Maximum line length for single line if-else expressions. A value of `0` (zero) results in if-else expressions always being broken into multiple lines. Note this occurs when `use_small_heuristics` is set to `Off`.
 
+Common if-else expressions that may be formatted on a single line are expressions on the right hand side of the equals (`=`) sign in a let statement, expressions inside a function call, and expressions inside a closure. If one of the if-else blocks contain a statement, a comment, an attribute, or is empty, the if-else expression will be broken into multiple lines. For backwards compatability reasons, an if-else expression at the end of a block is treated as a statement when using `version = "One"` and may not be formatted on a single line. When using `version = "Two"` an if-else expression at the end of a block may be formatted on a single line if it is a simple if-else expression as described earlier. As an example, the last if-else expression in the last snippet of this section would be formatted on a single line with `version = "Two"`.
+
 - **Default value**: `50`
 - **Possible values**: any positive integer that is less than or equal to the value specified for [`max_width`](#max_width)
 - **Stable**: Yes
 
 By default this option is set as a percentage of [`max_width`](#max_width) provided by [`use_small_heuristics`](#use_small_heuristics), but a value set directly for `single_line_if_else_max_width` will take precedence.
 
+#### `50` (default):
+
+```rust
+fn foo() -> usize {
+ let some_long_name = true;
+ let some_other_long_name = false;
+ fun(if some_long_name && some_other_long_name {
+ 0
+ } else {
+ 10
+ });
+ closure(|super_long_closure_variable| {
+ if super_long_closure_variable == 0 {
+ 0
+ } else {
+ 10
+ }
+ });
+ let bar = if some_long_name && some_other_long_name {
+ baz()
+ } else {
+ buzz()
+ };
+ if some_long_name && some_other_long_name {
+ 1
+ } else {
+ 2
+ }
+}
+```
+
+#### `70`:
+
+```rust
+fn foo() -> usize {
+ let some_long_name = true;
+ let some_other_long_name = false;
+ fun(if some_long_name && some_other_long_name { 0 } else { 10 });
+ closure(|super_long_closure_variable| if super_long_closure_variable == 0 { 0 } else { 10 });
+ let bar = if some_long_name && some_other_long_name { baz() } else { buzz() };
+ if some_long_name && some_other_long_name {
+ 1
+ } else {
+ 2
+ }
+}
+```
+
 See also [`max_width`](#max_width) and [`use_small_heuristics`](#use_small_heuristics)
 
 ## `space_after_colon`

tests/source/issue-5496/70.rs

@@ -0,0 +1,8 @@
+// rustfmt-version: One
+// rustfmt-single_line_if_else_max_width: 70
+fn foo() -> usize {
+ let some_long_name = true;
+ let some_other_long_name = false;
+ let bar = if some_long_name && some_other_long_name { baz() } else { buzz() };
+ if some_long_name && some_other_long_name { 1 } else { 2 }
+}

tests/source/issue-5496/70_version_two.rs

@@ -0,0 +1,12 @@
+// rustfmt-version: Two
+// rustfmt-single_line_if_else_max_width: 70
+fn foo() -> usize {
+ let some_long_name = true;
+ let some_other_long_name = false;
+ let bar = if some_long_name && some_other_long_name { baz() } else { buzz() };
+ if some_long_name && some_other_long_name {
+ 1
+ } else {
+ 2
+ }
+}

tests/source/issue-5496/default.rs

@@ -0,0 +1,6 @@
+fn foo() -> usize {
+ let some_long_name = true;
+ let some_other_long_name = false;
+ let bar = if some_long_name && some_other_long_name { baz() } else { buzz() };
+ if some_long_name && some_other_long_name { 1 } else { 2 }
+}

tests/source/issue-5496/nested_if_one.rs

@@ -0,0 +1,10 @@
+// rustfmt-version: One
+// rustfmt-single_line_if_else_max_width: 75
+fn foo() -> usize {
+ // nested
+ let _ = if true { if false { 1 } else { 2 } } else { 3 };
+ let _ = if true { 3 } else { if false { 1 } else { 2 } };
+ let _ = if true { if false { 1 } else { 2 } } else { if false { 3 } else { 4 } };
+
+ 1
+}

tests/source/issue-5496/nested_if_two.rs

@@ -0,0 +1,22 @@
+// rustfmt-version: Two
+// rustfmt-single_line_if_else_max_width: 75
+fn foo() -> usize {
+ // nested
+ let _ = if true {
+ if false { 1 } else { 2 }
+ } else {
+ 3
+ };
+ let _ = if true {
+ 3
+ } else {
+ if false { 1 } else { 2 }
+ };
+ let _ = if true {
+ if false { 1 } else { 2 }
+ } else {
+ if false { 3 } else { 4 }
+ };
+
+ 1
+}

tests/source/issue-5496/simple_one.rs

@@ -0,0 +1,24 @@
+// rustfmt-version: One
+fn foo() -> usize {
+ // empty
+ let _ = if true { 1 } else { };
+ let _ = if true { } else { 2 };
+ let _ = if true { } else { };
+
+ // attribute
+ let _ = if true { #[must_use] 1 } else { 2 };
+ let _ = if true { 1 } else { #[must_use] 2 };
+ let _ = if true { #[must_use] 1 } else { #[must_use] 2 };
+
+ // comment
+ let _ = if true { 1 /*1*/ } else { 2 };
+ let _ = if true { 1 } else { 2 /*2*/};
+ let _ = if true { 1 /*1*/} else { 2 /*2*/};
+
+ // a statement
+ let _ = if true { let a = 1; a } else { 2 };
+ let _ = if true { 1 } else { let b = 2; b };
+ let _ = if true { let a = 1; a } else { let b = 2; b };
+
+ 1
+}

tests/source/issue-5496/simple_two.rs

@@ -0,0 +1,24 @@
+// rustfmt-version: Two
+fn foo() -> usize {
+ // empty
+ let _ = if true { 1 } else { };
+ let _ = if true { } else { 2 };
+ let _ = if true { } else { };
+
+ // attribute
+ let _ = if true { #[must_use] 1 } else { 2 };
+ let _ = if true { 1 } else { #[must_use] 2 };
+ let _ = if true { #[must_use] 1 } else { #[must_use] 2 };
+
+ // comment
+ let _ = if true { 1 /*1*/ } else { 2 };
+ let _ = if true { 1 } else { 2 /*2*/};
+ let _ = if true { 1 /*1*/} else { 2 /*2*/};
+
+ // a statement
+ let _ = if true { let a = 1; a } else { 2 };
+ let _ = if true { 1 } else { let b = 2; b };
+ let _ = if true { let a = 1; a } else { let b = 2; b };
+
+ 1
+}

tests/target/issue-5496/70.rs

@@ -0,0 +1,12 @@
+// rustfmt-version: One
+// rustfmt-single_line_if_else_max_width: 70
+fn foo() -> usize {
+ let some_long_name = true;
+ let some_other_long_name = false;
+ let bar = if some_long_name && some_other_long_name { baz() } else { buzz() };
+ if some_long_name && some_other_long_name {
+ 1
+ } else {
+ 2
+ }
+}

tests/target/issue-5496/70_version_two.rs

@@ -0,0 +1,8 @@
+// rustfmt-version: Two
+// rustfmt-single_line_if_else_max_width: 70
+fn foo() -> usize {
+ let some_long_name = true;
+ let some_other_long_name = false;
+ let bar = if some_long_name && some_other_long_name { baz() } else { buzz() };
+ if some_long_name && some_other_long_name { 1 } else { 2 }
+}

tests/target/issue-5496/default.rs

@@ -0,0 +1,14 @@
+fn foo() -> usize {
+ let some_long_name = true;
+ let some_other_long_name = false;
+ let bar = if some_long_name && some_other_long_name {
+ baz()
+ } else {
+ buzz()
+ };
+ if some_long_name && some_other_long_name {
+ 1
+ } else {
+ 2
+ }
+}

tests/target/issue-5496/nested_if_one.rs

@@ -0,0 +1,38 @@
+// rustfmt-version: One
+// rustfmt-single_line_if_else_max_width: 75
+fn foo() -> usize {
+ // nested
+ let _ = if true {
+ if false {
+ 1
+ } else {
+ 2
+ }
+ } else {
+ 3
+ };
+ let _ = if true {
+ 3
+ } else {
+ if false {
+ 1
+ } else {
+ 2
+ }
+ };
+ let _ = if true {
+ if false {
+ 1
+ } else {
+ 2
+ }
+ } else {
+ if false {
+ 3
+ } else {
+ 4
+ }
+ };
+
+ 1
+}

tests/target/issue-5496/nested_if_two.rs

@@ -0,0 +1,22 @@
+// rustfmt-version: Two
+// rustfmt-single_line_if_else_max_width: 75
+fn foo() -> usize {
+ // nested
+ let _ = if true {
+ if false { 1 } else { 2 }
+ } else {
+ 3
+ };
+ let _ = if true {
+ 3
+ } else {
+ if false { 1 } else { 2 }
+ };
+ let _ = if true {
+ if false { 1 } else { 2 }
+ } else {
+ if false { 3 } else { 4 }
+ };
+
+ 1
+}

tests/target/issue-5496/simple_one.rs

@@ -0,0 +1,76 @@
+// rustfmt-version: One
+fn foo() -> usize {
+ // empty
+ let _ = if true {
+ 1
+ } else {
+ };
+ let _ = if true {
+ } else {
+ 2
+ };
+ let _ = if true {
+ } else {
+ };
+
+ // attribute
+ let _ = if true {
+ #[must_use]
+ 1
+ } else {
+ 2
+ };
+ let _ = if true {
+ 1
+ } else {
+ #[must_use]
+ 2
+ };
+ let _ = if true {
+ #[must_use]
+ 1
+ } else {
+ #[must_use]
+ 2
+ };
+
+ // comment
+ let _ = if true {
+ 1 /*1*/
+ } else {
+ 2
+ };
+ let _ = if true {
+ 1
+ } else {
+ 2 /*2*/
+ };
+ let _ = if true {
+ 1 /*1*/
+ } else {
+ 2 /*2*/
+ };
+
+ // a statement
+ let _ = if true {
+ let a = 1;
+ a
+ } else {
+ 2
+ };
+ let _ = if true {
+ 1
+ } else {
+ let b = 2;
+ b
+ };
+ let _ = if true {
+ let a = 1;
+ a
+ } else {
+ let b = 2;
+ b
+ };
+
+ 1
+}