fix rust-lang#6164: Reduce format failure for non default imports_granularity

This patch reduces format failure for non default `imports_granularity`
and correct the behavior around some edge cases.

- Supports too long line of `use ...` that contains `{}`.
- Fixes the width calculation of too long lines of `use ...`.

Author: kenoss

src/imports.rs

@@ -1110,8 +1110,8 @@ impl Rewrite for UseSegment {
                     // 1 = "{" and "}"
                     shape
                         .offset_left(1)
-                        .and_then(|s| s.sub_width(1))
-                        .unknown_error()?,
+                        .unknown_error()?
+                        .saturating_sub_width(1),
                 )?
             }
         })
@@ -1125,17 +1125,76 @@ impl Rewrite for UseTree {
 
     // This does NOT format attributes and visibility or add a trailing `;`.
     fn rewrite_result(&self, context: &RewriteContext<'_>, mut shape: Shape) -> RewriteResult {
+        fn proceed(
+            context: &RewriteContext<'_>,
+            shape: &Shape,
+            curr_segment: &UseSegment,
+            curr_segment_is_allow_overflow: bool,
+            next_segment: Option<&&UseSegment>,
+        ) -> Option<(String, Shape)> {
+            let mut rewritten_segment = curr_segment.rewrite(context, shape.clone())?;
+            if next_segment.is_some() {
+                rewritten_segment.push_str("::");
+            }
+            let reserved_room_for_brace = match next_segment.map(|s| &s.kind) {
+                Some(UseSegmentKind::List(_)) => "{".len(),
+                _ => 0,
+            };
+            let next_shape = if matches!(&curr_segment.kind, UseSegmentKind::List(_)) {
+                // This is the last segment and we won't use `next_shape`. Return `shape`
+                // unchanged.
+                shape.clone()
+            } else if curr_segment_is_allow_overflow {
+                // If the segment follows `use ` or newline, force to consume the segment with
+                // overflow.
+
+                let s = shape.offset_left_maybe_overflow(rewritten_segment.len());
+                if s.width == 0 {
+                    // We have to to commit current segment in this line. Make a room for next
+                    // round.
+                    s.add_width(reserved_room_for_brace)
+                } else {
+                    s.clone()
+                }
+            } else {
+                let ret = shape.offset_left(rewritten_segment.len())?;
+                // Check that there is a room for the next "{". If not, return null for retry with
+                // newline.
+                ret.offset_left(reserved_room_for_brace)?;
+                ret
+            };
+            Some((rewritten_segment, next_shape))
+        }
+
+        let shape_top_level = shape.clone();
         let mut result = String::with_capacity(256);
+        let mut is_first = true;
         let mut iter = self.path.iter().peekable();
         while let Some(segment) = iter.next() {
-            let segment_str = segment.rewrite_result(context, shape)?;
-            result.push_str(&segment_str);
-            if iter.peek().is_some() {
-                result.push_str("::");
-                // 2 = "::"
-                shape = shape
-                    .offset_left(2 + segment_str.len())
-                    .max_width_error(shape.width, self.span())?;
+            let allow_overflow = is_first;
+            is_first = false;
+            match proceed(context, &shape, segment, allow_overflow, iter.peek()) {
+                Some((rewritten_segment, next_shape)) => {
+                    result.push_str(&rewritten_segment);
+                    shape = next_shape;
+                    continue;
+                }
+                None => (),
+            }
+            // If the first `proceed()` failed, retry with newline.
+            result.push_str("\n");
+            result.push_str(&" ".repeat(shape.indent.block_indent + 4));
+            shape = shape_top_level.clone();
+            let allow_overflow = true;
+            match proceed(context, &shape, segment, allow_overflow, iter.peek()) {
+                Some((rewritten_segment, next_shape)) => {
+                    result.push_str(&rewritten_segment);
+                    shape = next_shape;
+                }
+                // Give up to format.
+                None => {
+                    return Err(crate::rewrite::RewriteError::Unknown);
+                }
             }
         }
         Ok(result)

src/shape.rs

@@ -242,6 +242,13 @@ impl Shape {
         })
     }
 
+    pub(crate) fn add_width(&self, width: usize) -> Shape {
+        Shape {
+            width: self.width + width,
+            ..*self
+        }
+    }
+
     pub(crate) fn shrink_left(&self, width: usize) -> Option<Shape> {
         Some(Shape {
             width: self.width.checked_sub(width)?,
@@ -254,6 +261,10 @@ impl Shape {
         self.add_offset(width).sub_width(width)
     }
 
+    pub(crate) fn offset_left_maybe_overflow(&self, width: usize) -> Shape {
+        self.add_offset(width).saturating_sub_width(width)
+    }
+
     pub(crate) fn used_width(&self) -> usize {
         self.indent.block_indent + self.offset
     }

tests/source/5131_crate.rs

@@ -12,3 +12,154 @@ use foo::d::e;
 use qux::h;
 use qux::h as h2;
 use qux::i;
+
+
+mod indent4 {
+    use column_____________________________________________________________________________________102::{
+        Foo,
+        bar::Bar,
+        bar::baz::Baz,
+        Foo2,
+        bar::Bar2,
+    };
+
+    use column_______________________________________________________________________________096::{
+        Foo,
+        bar::Bar,
+        bar::baz::Baz,
+        Foo2,
+        bar::Bar2,
+    };
+
+    use column_________________________________________________________________________090::{
+        Foo,
+        bar::Bar,
+        bar::baz::Baz,
+        Foo2,
+        bar::Bar2,
+    };
+
+    use c012::c018::c024::c030::c036::c042::c048::c054::c060::c066::c072::c078::c084::c090::c096::c102::{
+        Foo,
+        bar::Bar,
+        bar::baz::Baz,
+        Foo2,
+        bar::Bar2,
+    };
+
+    use c012::c018::c024::c030::c036::c042::c048::c054::c060::c066::c072::c078::c084::c090::c096::{
+        Foo,
+        bar::Bar,
+        bar::baz::Baz,
+        Foo2,
+        bar::Bar2,
+    };
+
+    use c012::c018::c024::c030::c036::c042::c048::c054::c060::c066::c072::c078::c084::c090::{
+        Foo,
+        bar::Bar,
+        bar::baz::Baz,
+        Foo2,
+        bar::Bar2,
+    };
+
+    use c012::c018::c024::c030::c036::c042::c048::c054::c060::c066::c072::c078::c084::{
+        Foo,
+        bar::Bar,
+        bar::baz::Baz,
+        Foo2,
+        bar::Bar2,
+    };
+}
+
+use smithay::{
+    backend::renderer::element::{
+        default_primary_scanout_output_compare, utils::select_dmabuf_feedback, RenderElementStates,
+    },
+    delegate_compositor, delegate_data_control, delegate_data_device, delegate_fractional_scale,
+    delegate_input_method_manager, delegate_keyboard_shortcuts_inhibit, delegate_layer_shell,
+    delegate_output, delegate_pointer_constraints, delegate_pointer_gestures,
+    delegate_presentation, delegate_primary_selection, delegate_relative_pointer, delegate_seat,
+    delegate_security_context, delegate_shm, delegate_tablet_manager, delegate_text_input_manager,
+    delegate_viewporter, delegate_virtual_keyboard_manager, delegate_xdg_activation,
+    delegate_xdg_decoration, delegate_xdg_shell,
+    desktop::{
+        space::SpaceElement,
+        utils::{
+            surface_presentation_feedback_flags_from_states, surface_primary_scanout_output,
+            update_surface_primary_scanout_output, OutputPresentationFeedback,
+        },
+        PopupKind, PopupManager, Space,
+    },
+    input::{
+        keyboard::{Keysym, LedState, XkbConfig},
+        pointer::{CursorImageStatus, PointerHandle},
+        Seat, SeatHandler, SeatState,
+    },
+    output::Output,
+    reexports::{
+        calloop::{generic::Generic, Interest, LoopHandle, Mode, PostAction},
+        wayland_protocols::xdg::decoration::{
+            self as xdg_decoration,
+            zv1::server::zxdg_toplevel_decoration_v1::Mode as DecorationMode,
+        },
+        wayland_server::{
+            backend::{ClientData, ClientId, DisconnectReason},
+            protocol::{wl_data_source::WlDataSource, wl_surface::WlSurface},
+            Display, DisplayHandle, Resource,
+        },
+    },
+    utils::{Clock, Monotonic, Rectangle},
+    wayland::{
+        compositor::{get_parent, with_states, CompositorClientState, CompositorState},
+        dmabuf::DmabufFeedback,
+        fractional_scale::{
+            with_fractional_scale, FractionalScaleHandler, FractionalScaleManagerState,
+        },
+        input_method::{InputMethodHandler, InputMethodManagerState, PopupSurface},
+        keyboard_shortcuts_inhibit::{
+            KeyboardShortcutsInhibitHandler, KeyboardShortcutsInhibitState,
+            KeyboardShortcutsInhibitor,
+        },
+        output::{OutputHandler, OutputManagerState},
+        pointer_constraints::{
+            with_pointer_constraint, PointerConstraintsHandler, PointerConstraintsState,
+        },
+        pointer_gestures::PointerGesturesState,
+        presentation::PresentationState,
+        relative_pointer::RelativePointerManagerState,
+        seat::WaylandFocus,
+        security_context::{
+            SecurityContext, SecurityContextHandler, SecurityContextListenerSource,
+            SecurityContextState,
+        },
+        selection::data_device::{
+            set_data_device_focus, ClientDndGrabHandler, DataDeviceHandler, DataDeviceState,
+            ServerDndGrabHandler,
+        },
+        selection::{
+            primary_selection::{
+                set_primary_focus, PrimarySelectionHandler, PrimarySelectionState,
+            },
+            wlr_data_control::{DataControlHandler, DataControlState},
+            SelectionHandler,
+        },
+        shell::{
+            wlr_layer::WlrLayerShellState,
+            xdg::{
+                decoration::{XdgDecorationHandler, XdgDecorationState},
+                ToplevelSurface, XdgShellState, XdgToplevelSurfaceData,
+            },
+        },
+        shm::{ShmHandler, ShmState},
+        socket::ListeningSocketSource,
+        tablet_manager::{TabletManagerState, TabletSeatTrait},
+        text_input::TextInputManagerState,
+        viewporter::ViewporterState,
+        virtual_keyboard::VirtualKeyboardManagerState,
+        xdg_activation::{
+            XdgActivationHandler, XdgActivationState, XdgActivationToken, XdgActivationTokenData,
+        },
+        xdg_foreign::{XdgForeignHandler, XdgForeignState},
+    },
+};