fix rust-lang#6164: Reduce format failure for non default `imports_gr…

…anularity`

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 ...`.

src/imports.rs

@@ -1068,7 +1068,7 @@ impl Rewrite for UseSegment {
                 context,
                 use_tree_list,
                 // 1 = "{" and "}"
-                shape.offset_left(1)?.sub_width(1)?,
+                shape.offset_left(1)?.saturating_sub_width(1),
             )?,
         })
     }
@@ -1077,15 +1077,75 @@ impl Rewrite for UseSegment {
 impl Rewrite for UseTree {
     // This does NOT format attributes and visibility or add a trailing `;`.
     fn rewrite(&self, context: &RewriteContext<'_>, mut shape: Shape) -> Option<String> {
+        let shape_top_level = shape.clone();
         let mut result = String::with_capacity(256);
+        let mut is_first = true;
+        let mut prev_is_allow_overflow = false;
         let mut iter = self.path.iter().peekable();
         while let Some(segment) = iter.next() {
-            let segment_str = segment.rewrite(context, shape)?;
-            result.push_str(&segment_str);
-            if iter.peek().is_some() {
-                result.push_str("::");
-                // 2 = "::"
-                shape = shape.offset_left(2 + segment_str.len())?;
+            // Try stacking the next segment, e.g. `use prev::next_segment::...` and
+            // `use prev::{next, segment}`.
+            let can_stack_with_constraint = (|| {
+                // If the segment follows `use ` or `{`, force to consume the segment with overflow.
+                if is_first {
+                    let mut chunk = segment.rewrite(context, shape.infinite_width())?;
+                    let next_shape = if iter.peek().is_some() {
+                        chunk.push_str("::");
+                        shape.offset_left_maybe_overflow(chunk.len())
+                    } else {
+                        shape.clone()
+                    };
+                    Some((chunk, next_shape))
+                } else {
+                    // If the segment follows `use ` or newline, allow overflow by "{".
+                    let s = if prev_is_allow_overflow
+                        && matches!(segment.kind, UseSegmentKind::List(_))
+                    {
+                        shape.add_width(1)
+                    } else {
+                        shape.clone()
+                    };
+                    let mut chunk = segment.rewrite(context, s)?;
+                    let next_shape = match iter.peek().map(|s| &s.kind) {
+                        Some(UseSegmentKind::List(_)) => {
+                            chunk.push_str("::");
+                            let ret = shape.offset_left(chunk.len())?;
+                            // Ensure that there is a room for the next "{".
+                            ret.offset_left(1)?;
+                            ret
+                        }
+                        Some(_) => {
+                            chunk.push_str("::");
+                            shape.offset_left(chunk.len())?
+                        }
+                        None => shape.clone(),
+                    };
+                    Some((chunk, next_shape))
+                }
+            })();
+            match can_stack_with_constraint {
+                Some((chunk, next_shape)) => {
+                    result.push_str(&chunk);
+                    shape = next_shape;
+                    prev_is_allow_overflow = is_first;
+                    is_first = false;
+                }
+                // If the next segment exceeds the given width, continue with newline.
+                None => {
+                    let segment_str = segment.rewrite(context, shape)?;
+                    let mut chunk = format!(
+                        "{}{}",
+                        " ".repeat(shape.indent.block_indent + 4),
+                        segment_str
+                    );
+                    if iter.peek().is_some() {
+                        chunk.push_str("::");
+                    }
+                    result.push_str("\n");
+                    result.push_str(&chunk);
+                    shape = shape_top_level.offset_left_maybe_overflow(segment_str.len());
+                    prev_is_allow_overflow = true;
+                }
             }
         }
         Some(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},
+    },
+};