Indentation of asssignment comments between lhs and rhs

Author: davidBar-On

src/comment.rs

@@ -12,7 +12,7 @@ use crate::rewrite::RewriteContext;
 use crate::shape::{Indent, Shape};
 use crate::string::{rewrite_string, StringFormat};
 use crate::utils::{
-    count_newlines, first_line_width, last_line_width, trim_left_preserve_layout,
+    count_newlines, first_line_width, is_single_line, last_line_width, trim_left_preserve_layout,
     trimmed_last_line_width, unicode_str_width,
 };
 use crate::{ErrorKind, FormattingError};
@@ -160,6 +160,18 @@ pub(crate) fn is_last_comment_block(s: &str) -> bool {
     s.trim_end().ends_with("*/")
 }
 
+/// Returns true if the first line of the passed string starts with a comment
+/// that end on that line.
+fn is_first_comment_ends_on_first_line(s: &str) -> bool {
+    if s.starts_with("/*") {
+        s.lines().next().map_or(false, |l| l.contains("*/"))
+    } else if s.starts_with("//") {
+        true
+    } else {
+        false
+    }
+}
+
 /// Combine `prev_str` and `next_str` into a single `String`. `span` may contain
 /// comments between two strings. If there are such comments, then that will be
 /// recovered. If `allow_extend` is true and there is no comment between the two
@@ -225,7 +237,13 @@ pub(crate) fn combine_strs_with_missing_comments(
         Cow::from("")
     } else {
         let one_line_width = last_line_width(prev_str) + first_line_width(&missing_comment) + 1;
-        if prefer_same_line && one_line_width <= shape.width {
+        // First comment of a comments block can be in same line if ends in the first line
+        // (and meets other conditions)
+        if prefer_same_line
+            && one_line_width <= shape.width
+            && (is_single_line(&missing_comment)
+                || is_first_comment_ends_on_first_line(&missing_comment))
+        {
             Cow::from(" ")
         } else {
             indent.to_string_with_newline(config)
@@ -240,7 +258,7 @@ pub(crate) fn combine_strs_with_missing_comments(
         indent.to_string_with_newline(config)
     } else {
         one_line_width += missing_comment.len() + first_sep.len() + 1;
-        allow_one_line &= !missing_comment.starts_with("//") && !missing_comment.contains('\n');
+        allow_one_line &= !missing_comment.contains('\n');
         if prefer_same_line && allow_one_line && one_line_width <= shape.width {
             Cow::from(" ")
         } else {
@@ -1001,24 +1019,29 @@ fn light_rewrite_comment(
     config: &Config,
     is_doc_comment: bool,
 ) -> String {
-    let lines: Vec<&str> = orig
+    let lines: Vec<String> = orig
         .lines()
         .map(|l| {
             // This is basically just l.trim(), but in the case that a line starts
             // with `*` we want to leave one space before it, so it aligns with the
             // `*` in `/*`.
             let first_non_whitespace = l.find(|c| !char::is_whitespace(c));
-            let left_trimmed = if let Some(fnw) = first_non_whitespace {
-                if l.as_bytes()[fnw] == b'*' && fnw > 0 {
-                    &l[fnw - 1..]
+            let (blank, left_trimmed) = if let Some(fnw) = first_non_whitespace {
+                if l.as_bytes()[fnw] == b'*' {
+                    // Ensure '*' is preceeded by blank and not by a tab.
+                    (" ", &l[fnw..])
                 } else {
-                    &l[fnw..]
+                    ("", &l[fnw..])
                 }
             } else {
-                ""
+                ("", "")
             };
             // Preserve markdown's double-space line break syntax in doc comment.
-            trim_end_unless_two_whitespaces(left_trimmed, is_doc_comment)
+            format!(
+                "{}{}",
+                blank,
+                trim_end_unless_two_whitespaces(left_trimmed, is_doc_comment),
+            )
         })
         .collect();
     lines.join(&format!("\n{}", offset.to_string(config)))

src/expr.rs

@@ -42,7 +42,7 @@ impl Rewrite for ast::Expr {
     }
 }
 
-#[derive(Copy, Clone, PartialEq)]
+#[derive(Copy, Clone, PartialEq, Debug)]
 pub(crate) enum ExprType {
     Statement,
     SubExpression,
@@ -171,11 +171,11 @@ pub(crate) fn format_expr(
         ast::ExprKind::Path(ref qself, ref path) => {
             rewrite_path(context, PathContext::Expr, qself.as_ref(), path, shape)
         }
-        ast::ExprKind::Assign(ref lhs, ref rhs, _) => {
-            rewrite_assignment(context, lhs, rhs, None, shape)
+        ast::ExprKind::Assign(ref lhs, ref rhs, op_span) => {
+            rewrite_assignment(context, lhs, rhs, op_span, shape)
         }
         ast::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
-            rewrite_assignment(context, lhs, rhs, Some(op), shape)
+            rewrite_assignment(context, lhs, rhs, op.span, shape)
         }
         ast::ExprKind::Continue(ref opt_label) => {
             let id_str = match *opt_label {
@@ -1893,24 +1893,24 @@ fn rewrite_assignment(
     context: &RewriteContext<'_>,
     lhs: &ast::Expr,
     rhs: &ast::Expr,
-    op: Option<&ast::BinOp>,
+    op_span: Span,
     shape: Shape,
 ) -> Option<String> {
-    let operator_str = match op {
-        Some(op) => context.snippet(op.span),
-        None => "=",
-    };
-
     // 1 = space between lhs and operator.
+    let operator_str = context.snippet(op_span);
     let lhs_shape = shape.sub_width(operator_str.len() + 1)?;
     let lhs_str = format!("{} {}", lhs.rewrite(context, lhs_shape)?, operator_str);
 
-    rewrite_assign_rhs(
+    let comments_span = mk_sp(op_span.hi(), rhs.span.lo());
+    rewrite_assign_rhs_with_comments(
         context,
         lhs_str,
         rhs,
-        &RhsAssignKind::Expr(&rhs.kind, rhs.span),
         shape,
+        &RhsAssignKind::Expr(&rhs.kind, rhs.span),
+        RhsTactics::Default,
+        comments_span,
+        true,
     )
 }
 

src/items.rs

@@ -113,17 +113,57 @@ impl Rewrite for ast::Local {
         result.push_str(&infix);
 
         if let Some((init, _els)) = self.kind.init_else_opt() {
+            let base_span = if let Some(ref ty) = self.ty {
+                mk_sp(ty.span.hi(), self.span.hi())
+            } else {
+                mk_sp(self.pat.span.hi(), self.span.hi())
+            };
+
+            let offset = context.snippet(base_span).find_uncommented("=")?;
+            let base_span_lo = base_span.lo();
+
+            let assign_lo = base_span_lo + BytePos(offset as u32);
+            let comment_start_pos = if let Some(ref ty) = self.ty {
+                ty.span.hi()
+            } else {
+                self.pat.span.hi()
+            };
+            let comment_before_assign = context.snippet(mk_sp(comment_start_pos, assign_lo)).trim();
+
+            let assign_hi = base_span_lo + BytePos((offset + 1) as u32);
+            let rhs_span_lo = init.span.lo();
+            let comment_end_pos = if init.attrs.is_empty() {
+                rhs_span_lo
+            } else {
+                let attr_span_lo = init.attrs.first().unwrap().span.lo();
+                // for the case using block
+                // ex. let x = { #![my_attr]do_something(); }
+                if rhs_span_lo < attr_span_lo {
+                    rhs_span_lo
+                } else {
+                    attr_span_lo
+                }
+            };
+
+            if !comment_before_assign.is_empty() {
+                let new_indent_str = &pat_shape
+                    .block_indent(0)
+                    .to_string_with_newline(context.config);
+                result = format!("{}{}{}", comment_before_assign, new_indent_str, result);
+            }
+
             // 1 = trailing semicolon;
             let nested_shape = shape.sub_width(1)?;
-
-            result = rewrite_assign_rhs(
+            result = rewrite_assign_rhs_with_comments(
                 context,
                 result,
                 init,
-                &RhsAssignKind::Expr(&init.kind, init.span),
                 nested_shape,
+                &RhsAssignKind::Expr(&init.kind, init.span),
+                RhsTactics::Default,
+                mk_sp(assign_hi, comment_end_pos),
+                true,
             )?;
-            // todo else
         }
 
         result.push(';');

tests/source/lhs-to-rhs-between-comments/assignment-multi-line-comments.rs

@@ -0,0 +1,75 @@
+// "=" Assignemnt - Multiline Block comments
+fn main () {
+let var = /* Block comment line 1 
+* Block comment line 2
+* Block comment line 3 */ first;
+var = /* Block comment line 1 
+* Block comment line 2
+* Block comment line 3 */ second;
+var = /* Block comment line 1 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+* Block comment line 2
+* Block comment line 3 */ third;
+var = /* Block comment line 1 
+* Block comment line 2 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+* Block comment line 3 */ forth;
+}
+
+// "=" Assignemnt - Multiline Line and Block comments
+fn main () {
+let var = // Line comment 1
+// Line comment 2
+// Line comment 3
+first;
+var = // Line comment 
+/* Block comment line 1
+* Block comment line 2 */ second;
+var = /* Block comment single line */ 
+// Line comment
+/* Block comment line 1
+* Block comment line 2 */ third;
+var = /* Block comment line 1 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+* Block comment line 2 */
+// Line comment
+forth;
+var = // Line comment 
+/* Block comment line 1 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+* Block comment line 2 */ fifth;
+}
+
+// BinOp Assignemnt - Multiline Block comments
+fn main () {
+let var = /* Block comment line 1 
+* Block comment line 2
+* Block comment line 3 */ first;
+var += /* Block comment line 1 
+* Block comment line 2
+* Block comment line 3 */ second;
+var -= /* Block comment line 1 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+* Block comment line 2
+* Block comment line 3 */ third;
+var *= /* Block comment line 1 
+* Block comment line 2 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+* Block comment line 3 */ forth;
+}
+
+// BinOp Assignemnt - Multiline Line and Block comments
+fn main () {
+let var = // Line comment 1
+// Line comment 2
+// Line comment 3
+first;
+var += // Line comment 
+/* Block comment line 1
+* Block comment line 2 */ second;
+var -= /* Block comment single line */ 
+// Line comment
+/* Block comment line 1
+* Block comment line 2 */ third;
+var *= /* Block comment line 1 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+* Block comment line 2 */
+// Line comment
+forth;
+var /= // Line comment 
+/* Block comment line 1 longggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg
+* Block comment line 2 */ fifth;
+}

tests/source/lhs-to-rhs-between-comments/assignment-single-line-comments.rs

@@ -0,0 +1,47 @@
+// "=" Assignemnt
+fn main () {
+let var = first;
+var = second;
+}
+fn main () {
+let var = /* Block comment */ first;
+var = /* Block comment */ second;
+}
+fn main () {
+let var = // Line comment
+first;
+var = // Line comment
+second;
+}
+fn main () {
+let var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ first;
+var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ second;
+}
+fn main () {
+let var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ first;
+var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ second;
+}
+
+// BinOp Assigment
+fn main () {
+let var = first;
+var += second;
+}
+fn main () {
+let var = /* Block comment */ first;
+var -= /* Block comment */ second;
+}
+fn main () {
+let var = // Line comment
+first;
+var *= // Line comment
+second;
+}
+fn main () {
+let var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ first;
+var /= /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ second;
+}
+fn main () {
+let var = /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ first;
+var /= /* Block comment longgggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg */ second;
+}