From 6d441d32381037401642a204ddb8eccc71f4e4c5 Mon Sep 17 00:00:00 2001
From: Graydon Hoare <graydon@mozilla.com>
Date: Thu, 30 Jun 2011 17:25:13 -0700
Subject: [PATCH] Preserve hard \n\n pairs from source when pretty-printing, as
 explicit formatting control from users.

---
 src/comp/front/lexer.rs   | 24 ++++++++++++++++++++----
 src/comp/pretty/ppaux.rs  |  5 +++++
 src/comp/pretty/pprust.rs | 16 +++++++---------
 3 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/src/comp/front/lexer.rs b/src/comp/front/lexer.rs
index c688f79d7ca..d6bc3723bf3 100644
--- a/src/comp/front/lexer.rs
+++ b/src/comp/front/lexer.rs
@@ -536,6 +536,8 @@ fn binop(&reader rdr, token::binop op) -> token::token {
 
     mixed; // Code before /* foo */ and after the comment
 
+    blank_line; // Just a manual blank linke "\n\n", for layout
+
 }
 
 type cmnt = rec(cmnt_style style, vec[str] lines, uint pos);
@@ -546,7 +548,6 @@ fn read_to_eol(&reader rdr) -> str {
         str::push_char(val, rdr.curr());
         rdr.bump();
     }
-    if (rdr.curr() == '\n') { rdr.bump(); } else { assert (rdr.is_eof()); }
     ret val;
 }
 
@@ -566,6 +567,19 @@ fn consume_non_eol_whitespace(&reader rdr) {
     }
 }
 
+fn consume_whitespace_counting_blank_lines(&reader rdr,
+                                           &mutable vec[cmnt] comments) {
+    while (is_whitespace(rdr.curr()) && !rdr.is_eof()) {
+        if (rdr.curr() == '\n' && rdr.next() == '\n') {
+            log ">>> blank-line comment";
+            let vec[str] v = [];
+            comments += [rec(style=blank_line, lines=v,
+                             pos=rdr.get_chpos())];
+        }
+        rdr.bump();
+    }
+}
+
 fn read_line_comments(&reader rdr, bool code_to_the_left) -> cmnt {
     log ">>> line comments";
     auto p = rdr.get_chpos();
@@ -694,19 +708,21 @@ fn gather_comments_and_literals(session sess, str path) ->
             consume_non_eol_whitespace(rdr);
             if (rdr.curr() == '\n') {
                 code_to_the_left = false;
-                consume_whitespace(rdr);
+                consume_whitespace_counting_blank_lines(rdr, comments);
             }
             while (peeking_at_comment(rdr)) {
                 consume_comment(rdr, code_to_the_left, comments);
-                consume_whitespace(rdr);
+                consume_whitespace_counting_blank_lines(rdr, comments);
             }
             break;
         }
-        if (is_lit(next_token(rdr))) {
+        auto tok = next_token(rdr);
+        if (is_lit(tok)) {
             vec::push[lit](literals,
                            rec(lit=rdr.get_mark_str(),
                                pos=rdr.get_mark_chpos()));
         }
+        log "tok: " + token::to_str(rdr, tok);
         first_read = false;
     }
     ret rec(cmnts=comments, lits=literals);
diff --git a/src/comp/pretty/ppaux.rs b/src/comp/pretty/ppaux.rs
index f0ebac66dbd..05cd539e00c 100644
--- a/src/comp/pretty/ppaux.rs
+++ b/src/comp/pretty/ppaux.rs
@@ -279,6 +279,11 @@ fn print_comment(&ps s, lexer::cmnt cmnt) {
                 end(s);
             }
         }
+        case (lexer::blank_line) {
+            // We need to do at least one, possibly two hardbreaks.
+            pprust::hardbreak_if_not_bol(s);
+            hardbreak(s.s);
+        }
     }
 }
 
diff --git a/src/comp/pretty/pprust.rs b/src/comp/pretty/pprust.rs
index 9cc017a221f..ca5b283c38d 100644
--- a/src/comp/pretty/pprust.rs
+++ b/src/comp/pretty/pprust.rs
@@ -191,9 +191,7 @@ fn print_mod(&ps s, ast::_mod _mod, &vec[ast::attribute] attrs) {
         print_view_item(s, vitem);
     }
     for (@ast::item item in _mod.items) {
-        // Mod-level item printing we're a little more space-y about.
-        hardbreak(s.s);
-        hardbreak(s.s);
+        hardbreak_if_not_bol(s);
         print_item(s, item);
     }
     print_remaining_comments(s);
@@ -271,7 +269,7 @@ fn print_field(&ps s, &ast::ty_field f) {
             head(s, "obj");
             bopen(s);
             for (ast::ty_method m in methods) {
-                hardbreak(s.s);
+                hardbreak_if_not_bol(s);
                 cbox(s, indent_unit);
                 maybe_print_comment(s, m.span.lo);
                 print_ty_fn(s, m.node.proto, some(m.node.ident),
@@ -338,7 +336,7 @@ fn print_item(&ps s, &@ast::item item) {
             word_nbsp(s, item.ident);
             bopen(s);
             for (@ast::native_item item in nmod.items) {
-                hardbreak(s.s);
+                hardbreak_if_not_bol(s);
                 ibox(s, indent_unit);
                 maybe_print_comment(s, item.span.lo);
                 alt (item.node) {
@@ -427,7 +425,7 @@ fn print_field(&ps s, &ast::obj_field field) {
             bopen(s);
             for (@ast::method meth in _obj.methods) {
                 let vec[ast::ty_param] typarams = [];
-                hardbreak(s.s);
+                hardbreak_if_not_bol(s);
                 maybe_print_comment(s, meth.span.lo);
                 print_fn(s, meth.node.meth.decl, meth.node.meth.proto,
                          meth.node.ident, typarams);
@@ -475,7 +473,7 @@ fn print_outer_attributes(&ps s, vec[ast::attribute] attrs) {
             case (_) {/* fallthrough */ }
         }
     }
-    if (count > 0) { hardbreak(s.s); }
+    if (count > 0) { hardbreak_if_not_bol(s); }
 }
 
 fn print_inner_attributes(&ps s, vec[ast::attribute] attrs) {
@@ -490,11 +488,11 @@ fn print_inner_attributes(&ps s, vec[ast::attribute] attrs) {
             case (_) { /* fallthrough */ }
         }
     }
-    if (count > 0) { hardbreak(s.s); }
+    if (count > 0) { hardbreak_if_not_bol(s); }
 }
 
 fn print_attribute(&ps s, &ast::attribute attr) {
-    hardbreak(s.s);
+    hardbreak_if_not_bol(s);
     maybe_print_comment(s, attr.span.lo);
     word(s.s, "#[");
     print_meta_item(s, @attr.node.value);