feat(rome_js_formatter): Member chain formatting

crates/rome_formatter/src/arguments.rs

@@ -150,7 +150,7 @@ mod tests {
                 FormatElement::Text(Text::Static { text: "a" }),
                 FormatElement::Space,
                 // Group
-                FormatElement::Tag(Tag::StartGroup(None)),
+                FormatElement::Tag(Tag::StartGroup(tag::Group::new())),
                 FormatElement::Text(Text::Static { text: "(" }),
                 FormatElement::Text(Text::Static { text: ")" }),
                 FormatElement::Tag(Tag::EndGroup)

crates/rome_formatter/src/builders.rs

@@ -1,5 +1,5 @@
 use crate::format_element::tag::{Condition, Tag};
-use crate::prelude::tag::{DedentMode, LabelId};
+use crate::prelude::tag::{DedentMode, GroupMode, LabelId};
 use crate::prelude::*;
 use crate::{format_element, write, Argument, Arguments, GroupId, TextRange, TextSize};
 use crate::{Buffer, VecBuffer};
@@ -1332,14 +1332,12 @@ impl<Context> Group<'_, Context> {
         self
     }
 
-    /// Setting the value to `true` forces the group and its enclosing group to expand regardless if it otherwise would fit on the
-    /// line or contains any hard line breaks.
+    /// Changes the [PrintMode] of the group from [`Flat`](PrintMode::Flat) to [`Expanded`](PrintMode::Expanded).
+    /// The result is that any soft-line break gets printed as a regular line break.
     ///
-    /// The formatter writes a [FormatElement::ExpandParent], forcing any enclosing group to expand, if `should_expand` is `true`.
-    /// It also omits the [`start`](Tag::StartGroup) and [`end`](Tag::EndGroup) tags because the group would be forced to expand anyway.
-    /// The [`start`](Tag::StartGroup) and [`end`](Tag::EndGroup) tags are only written if the `group_id` specified with [Group::with_group_id] isn't [None]
-    /// because other IR elements may reference the group with that group id and the printer may panic
-    /// if no group with the given id is present in the document.
+    /// This is useful for content rendered inside of a [FormatElement::BestFitting] that prints each variant
+    /// in [PrintMode::Flat] to change some content to be printed in [`Expanded`](PrintMode::Expanded) regardless.
+    /// See the documentation of the [`best_fitting`] macro for an example.
     pub fn should_expand(mut self, should_expand: bool) -> Self {
         self.should_expand = should_expand;
         self
@@ -1348,28 +1346,18 @@ impl<Context> Group<'_, Context> {
 
 impl<Context> Format<Context> for Group<'_, Context> {
     fn fmt(&self, f: &mut Formatter<Context>) -> FormatResult<()> {
-        if self.group_id.is_none() && self.should_expand {
-            write!(f, [expand_parent()])?;
-            return f.write_fmt(Arguments::from(&self.content));
-        }
-
-        let write_group = !self.should_expand || self.group_id.is_some();
-
-        if write_group {
-            f.write_element(FormatElement::Tag(Tag::StartGroup(self.group_id)))?;
-        }
+        let mode = match self.should_expand {
+            true => GroupMode::Expand,
+            false => GroupMode::Flat,
+        };
 
-        if self.should_expand {
-            write!(f, [expand_parent()])?;
-        }
+        f.write_element(FormatElement::Tag(StartGroup(
+            tag::Group::new().with_id(self.group_id).with_mode(mode),
+        )))?;
 
         Arguments::from(&self.content).fmt(f)?;
 
-        if write_group {
-            f.write_element(FormatElement::Tag(Tag::EndGroup))?;
-        }
-
-        Ok(())
+        f.write_element(FormatElement::Tag(EndGroup))
     }
 }
 
@@ -1438,7 +1426,7 @@ impl<Context> Format<Context> for ExpandParent {
 ///
 /// The element has no special meaning if used outside of a `Group`. In that case, the content is always emitted.
 ///
-/// If you're looking for a way to only print something if the `Group` fits on a single line see [crate::if_group_fits_on_line].
+/// If you're looking for a way to only print something if the `Group` fits on a single line see [self::if_group_fits_on_line].
 ///
 /// # Examples
 ///
@@ -2119,21 +2107,26 @@ where
 /// Get the number of line breaks between two consecutive SyntaxNodes in the tree
 pub fn get_lines_before<L: Language>(next_node: &SyntaxNode<L>) -> usize {
     // Count the newlines in the leading trivia of the next node
-    if let Some(leading_trivia) = next_node.first_leading_trivia() {
-        leading_trivia
-            .pieces()
-            .take_while(|piece| {
-                // Stop at the first comment or skipped piece, the comment printer
-                // will handle newlines between the comment and the node
-                !(piece.is_comments() || piece.is_skipped())
-            })
-            .filter(|piece| piece.is_newline())
-            .count()
+    if let Some(token) = next_node.first_token() {
+        get_lines_before_token(&token)
     } else {
         0
     }
 }
 
+pub fn get_lines_before_token<L: Language>(token: &SyntaxToken<L>) -> usize {
+    token
+        .leading_trivia()
+        .pieces()
+        .take_while(|piece| {
+            // Stop at the first comment or skipped piece, the comment printer
+            // will handle newlines between the comment and the node
+            !(piece.is_comments() || piece.is_skipped())
+        })
+        .filter(|piece| piece.is_newline())
+        .count()
+}
+
 /// Builder to fill as many elements as possible on a single line.
 #[must_use = "must eventually call `finish()` on Format builders"]
 pub struct FillBuilder<'fmt, 'buf, Context> {

crates/rome_formatter/src/format_element.rs

@@ -2,31 +2,31 @@ pub mod document;
 pub mod tag;
 
 use crate::format_element::tag::{LabelId, Tag};
+use std::borrow::Cow;
 
 use crate::{TagKind, TextSize};
 #[cfg(target_pointer_width = "64")]
 use rome_rowan::static_assert;
 use rome_rowan::SyntaxTokenText;
-use std::borrow::Cow;
 use std::hash::{Hash, Hasher};
 use std::ops::Deref;
 use std::rc::Rc;
 
 /// Language agnostic IR for formatting source code.
 ///
-/// Use the helper functions like [crate::space], [crate::soft_line_break] etc. defined in this file to create elements.
+/// Use the helper functions like [crate::builders::space], [crate::builders::soft_line_break] etc. defined in this file to create elements.
 #[derive(Clone, Eq, PartialEq)]
 pub enum FormatElement {
-    /// A space token, see [crate::space] for documentation.
+    /// A space token, see [crate::builders::space] for documentation.
     Space,
 
-    /// A new line, see [crate::soft_line_break], [crate::hard_line_break], and [crate::soft_line_break_or_space] for documentation.
+    /// A new line, see [crate::builders::soft_line_break], [crate::builders::hard_line_break], and [crate::builders::soft_line_break_or_space] for documentation.
     Line(LineMode),
 
     /// Forces the parent group to print in expanded mode.
     ExpandParent,
 
-    /// A text that should be printed as is, see [crate::text] for documentation and examples.
+    /// A text that should be printed as is, see [crate::builders::text] for documentation and examples.
     Text(Text),
 
     /// Prevents that line suffixes move past this boundary. Forces the printer to print any pending
@@ -66,13 +66,13 @@ impl std::fmt::Debug for FormatElement {
 
 #[derive(Debug, Clone, Copy, Eq, PartialEq)]
 pub enum LineMode {
-    /// See [crate::soft_line_break_or_space] for documentation.
+    /// See [crate::builders::soft_line_break_or_space] for documentation.
     SoftOrSpace,
-    /// See [crate::soft_line_break] for documentation.
+    /// See [crate::builders::soft_line_break] for documentation.
     Soft,
-    /// See [crate::hard_line_break] for documentation.
+    /// See [crate::builders::hard_line_break] for documentation.
     Hard,
-    /// See [crate::empty_line] for documentation.
+    /// See [crate::builders::empty_line] for documentation.
     Empty,
 }
 
@@ -140,7 +140,7 @@ impl Deref for Interned {
     }
 }
 
-/// See [crate::text] for documentation
+/// See [crate::builders::text] for documentation
 #[derive(Eq, Clone)]
 pub enum Text {
     /// Token constructed by the formatter from a static string
@@ -274,13 +274,16 @@ impl FormatElements for FormatElement {
     fn will_break(&self) -> bool {
         match self {
             FormatElement::ExpandParent => true,
+            FormatElement::Tag(Tag::StartGroup(group)) => !group.mode().is_flat(),
             FormatElement::Line(line_mode) => matches!(line_mode, LineMode::Hard | LineMode::Empty),
             FormatElement::Text(text) => text.contains('\n'),
             FormatElement::Interned(interned) => interned.will_break(),
-            FormatElement::LineSuffixBoundary
-            | FormatElement::Space
-            | FormatElement::Tag(_)
-            | FormatElement::BestFitting(_) => false,
+            // Traverse into the most flat version because the content is guaranteed to expand when even
+            // the most flat version contains some content that forces a break.
+            FormatElement::BestFitting(best_fitting) => best_fitting.most_flat().will_break(),
+            FormatElement::LineSuffixBoundary | FormatElement::Space | FormatElement::Tag(_) => {
+                false
+            }
         }
     }
 
@@ -371,7 +374,7 @@ impl std::fmt::Debug for BestFitting {
 pub trait FormatElements {
     /// Returns true if this [FormatElement] is guaranteed to break across multiple lines by the printer.
     /// This is the case if this format element recursively contains a:
-    /// * [crate::empty_line] or [crate::hard_line_break]
+    /// * [crate::builders::empty_line] or [crate::builders::hard_line_break]
     /// * A token containing '\n'
     ///
     /// Use this with caution, this is only a heuristic and the printer may print the element over multiple
@@ -399,8 +402,13 @@ mod tests {
     #[test]
     fn test_normalize_newlines() {
         assert_eq!(normalize_newlines("a\nb", LINE_TERMINATORS), "a\nb");
+        assert_eq!(normalize_newlines("a\n\n\nb", LINE_TERMINATORS), "a\n\n\nb");
         assert_eq!(normalize_newlines("a\rb", LINE_TERMINATORS), "a\nb");
         assert_eq!(normalize_newlines("a\r\nb", LINE_TERMINATORS), "a\nb");
+        assert_eq!(
+            normalize_newlines("a\r\n\r\n\r\nb", LINE_TERMINATORS),
+            "a\n\n\nb"
+        );
         assert_eq!(normalize_newlines("a\u{2028}b", LINE_TERMINATORS), "a\nb");
         assert_eq!(normalize_newlines("a\u{2029}b", LINE_TERMINATORS), "a\nb");
     }

crates/rome_formatter/src/format_element/document.rs

@@ -1,5 +1,6 @@
 use super::tag::Tag;
 use crate::format_element::tag::DedentMode;
+use crate::prelude::tag::GroupMode;
 use crate::prelude::*;
 use crate::printer::LineEnding;
 use crate::{format, write};
@@ -8,6 +9,7 @@ use crate::{
     IndentStyle, LineWidth, PrinterOptions, TransformSourceMap,
 };
 use rome_rowan::TextSize;
+use rustc_hash::FxHashMap;
 use std::collections::HashMap;
 use std::ops::Deref;
 
@@ -17,6 +19,87 @@ pub struct Document {
     elements: Vec<FormatElement>,
 }
 
+impl Document {
+    /// Sets [`expand`](tag::Group::expand) to [`GroupMode::Propagated`] if the group contains any of:
+    /// * a group with [`expand`](tag::Group::expand) set to [GroupMode::Propagated] or [GroupMode::Expand].
+    /// * a non-soft [line break](FormatElement::Line) with mode [LineMode::Hard], [LineMode::Empty], or [LineMode::Literal].
+    /// * a [FormatElement::ExpandParent]
+    ///
+    /// [`BestFitting`] elements act as expand boundaries, meaning that the fact that a
+    /// [`BestFitting`]'s content expands is not propagated past the [`BestFitting`] element.
+    ///
+    /// [`BestFitting`]: FormatElement::BestFitting
+    pub(crate) fn propagate_expand(&mut self) {
+        #[derive(Debug)]
+        enum Enclosing<'a> {
+            Group(&'a tag::Group),
+            BestFitting,
+        }
+
+        fn expand_parent(enclosing: &[Enclosing]) {
+            if let Some(Enclosing::Group(group)) = enclosing.last() {
+                group.propagate_expand();
+            }
+        }
+
+        fn propagate_expands<'a>(
+            elements: &'a [FormatElement],
+            enclosing: &mut Vec<Enclosing<'a>>,
+            checked_interned: &mut FxHashMap<&'a Interned, bool>,
+        ) -> bool {
+            let mut expands = false;
+            for element in elements {
+                let element_expands = match element {
+                    FormatElement::Tag(Tag::StartGroup(group)) => {
+                        enclosing.push(Enclosing::Group(group));
+                        false
+                    }
+                    FormatElement::Tag(Tag::EndGroup) => match enclosing.pop() {
+                        Some(Enclosing::Group(group)) => !group.mode().is_flat(),
+                        _ => false,
+                    },
+                    FormatElement::Interned(interned) => match checked_interned.get(interned) {
+                        Some(interned_expands) => *interned_expands,
+                        None => {
+                            let interned_expands =
+                                propagate_expands(interned, enclosing, checked_interned);
+                            checked_interned.insert(interned, interned_expands);
+                            interned_expands
+                        }
+                    },
+                    FormatElement::BestFitting(best_fitting) => {
+                        enclosing.push(Enclosing::BestFitting);
+
+                        for variant in best_fitting.variants() {
+                            propagate_expands(variant, enclosing, checked_interned);
+                        }
+
+                        // Best fitting acts as a boundary
+                        expands = false;
+                        enclosing.pop();
+                        continue;
+                    }
+                    FormatElement::Text(text) => text.contains('\n'),
+                    FormatElement::ExpandParent
+                    | FormatElement::Line(LineMode::Hard | LineMode::Empty) => true,
+                    _ => false,
+                };
+
+                if element_expands {
+                    expands = true;
+                    expand_parent(enclosing)
+                }
+            }
+
+            expands
+        }
+
+        let mut enclosing: Vec<Enclosing> = Vec::new();
+        let mut interned: FxHashMap<&Interned, bool> = FxHashMap::default();
+        propagate_expands(self, &mut enclosing, &mut interned);
+    }
+}
+
 impl From<Vec<FormatElement>> for Document {
     fn from(elements: Vec<FormatElement>) -> Self {
         Self { elements }
@@ -292,10 +375,10 @@ impl Format<IrFormatContext> for &[FormatElement] {
                             write!(f, [text("verbatim(")])?;
                         }
 
-                        StartGroup(id) => {
+                        StartGroup(group) => {
                             write!(f, [text("group(")])?;
 
-                            if let Some(group_id) = id {
+                            if let Some(group_id) = group.id() {
                                 write!(
                                     f,
                                     [
@@ -308,6 +391,16 @@ impl Format<IrFormatContext> for &[FormatElement] {
                                     ]
                                 )?;
                             }
+
+                            match group.mode() {
+                                GroupMode::Flat => {}
+                                GroupMode::Expand => {
+                                    write!(f, [text("expand: true,"), space()])?;
+                                }
+                                GroupMode::Propagated => {
+                                    write!(f, [text("expand: propagated,"), space()])?;
+                                }
+                            }
                         }
 
                         StartIndentIfGroupBreaks(id) => {
@@ -351,12 +444,12 @@ impl Format<IrFormatContext> for &[FormatElement] {
                             write!(
                                 f,
                                 [
-                                    text("label(\""),
+                                    text("label("),
                                     dynamic_text(
                                         &std::format!("\"{label_id:?}\""),
                                         TextSize::default()
                                     ),
-                                    text("\","),
+                                    text(","),
                                     space(),
                                 ]
                             )?;
@@ -420,7 +513,7 @@ impl Format<IrFormatContext> for ContentArrayStart {
         write!(f, [text("[")])?;
 
         f.write_elements([
-            FormatElement::Tag(StartGroup(None)),
+            FormatElement::Tag(StartGroup(tag::Group::new())),
             FormatElement::Tag(StartIndent),
             FormatElement::Line(LineMode::Soft),
         ])
@@ -585,7 +678,7 @@ mod tests {
 
         let document = Document::from(vec![
             FormatElement::Text(Text::Static { text: "[" }),
-            FormatElement::Tag(StartGroup(None)),
+            FormatElement::Tag(StartGroup(tag::Group::new())),
             FormatElement::Tag(StartIndent),
             FormatElement::Line(LineMode::Soft),
             FormatElement::Text(Text::Static { text: "a" }),