Merge pull request #2136 from topecongiro/issue-2025

Remove empty lines at the beginning of the file

src/codemap.rs

@@ -34,6 +34,7 @@ pub trait SpanUtils {
     fn span_after(&self, original: Span, needle: &str) -> BytePos;
     fn span_after_last(&self, original: Span, needle: &str) -> BytePos;
     fn span_before(&self, original: Span, needle: &str) -> BytePos;
+    fn opt_span_after(&self, original: Span, needle: &str) -> Option<BytePos>;
 }
 
 pub trait LineRangeUtils {
@@ -70,6 +71,13 @@ fn span_before(&self, original: Span, needle: &str) -> BytePos {
 
         original.lo() + BytePos(offset as u32)
     }
+
+    fn opt_span_after(&self, original: Span, needle: &str) -> Option<BytePos> {
+        let snippet = self.span_to_snippet(original).ok()?;
+        let offset = snippet.find_uncommented(needle)? + needle.len();
+
+        Some(original.lo() + BytePos(offset as u32))
+    }
 }
 
 impl LineRangeUtils for CodeMap {

src/lib.rs

@@ -321,6 +321,7 @@ fn format_ast<F>(
         let filemap = visitor.codemap.lookup_char_pos(module.inner.lo()).file;
         // Format inner attributes if available.
         if !krate.attrs.is_empty() && path == main_file {
+            visitor.skip_empty_lines(filemap.end_pos);
             if visitor.visit_attrs(&krate.attrs, ast::AttrStyle::Inner) {
                 visitor.push_rewrite(module.inner, None);
             } else {
@@ -328,6 +329,7 @@ fn format_ast<F>(
             }
         } else {
             visitor.last_pos = filemap.start_pos;
+            visitor.skip_empty_lines(filemap.end_pos);
             visitor.format_separate_mod(module, &*filemap);
         };
 

src/visitor.rs

@@ -510,6 +510,10 @@ pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisi
         }
     }
 
+    pub fn opt_snippet(&self, span: Span) -> Option<String> {
+        self.codemap.span_to_snippet(span).ok()
+    }
+
     pub fn snippet(&self, span: Span) -> String {
         match self.codemap.span_to_snippet(span) {
             Ok(s) => s,
@@ -695,6 +699,20 @@ pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap)
         self.format_missing_with_indent(filemap.end_pos);
     }
 
+    pub fn skip_empty_lines(&mut self, end_pos: BytePos) {
+        while let Some(pos) = self.codemap
+            .opt_span_after(mk_sp(self.last_pos, end_pos), "\n")
+        {
+            if let Some(snippet) = self.opt_snippet(mk_sp(self.last_pos, pos)) {
+                if snippet.trim().is_empty() {
+                    self.last_pos = pos;
+                } else {
+                    return;
+                }
+            }
+        }
+    }
+
     pub fn get_context(&self) -> RewriteContext {
         RewriteContext {
             parse_session: self.parse_session,

tests/source/issue-2025.rs

@@ -0,0 +1,8 @@
+
+
+
+
+// See if rustfmt removes empty lines on top of the file.
+pub fn foo() {
+    println!("hello, world");
+}

tests/target/issue-2025.rs

@@ -0,0 +1,4 @@
+// See if rustfmt removes empty lines on top of the file.
+pub fn foo() {
+    println!("hello, world");
+}

tests/target/loop.rs

@@ -1,4 +1,3 @@
-
 fn main() {
     loop {
         return some_val;

tests/target/nestedmod/mod.rs

@@ -1,4 +1,3 @@
-
 mod mod2a;
 mod mod2b;
 

tests/target/nestedmod/mod2b.rs

@@ -1,3 +1,2 @@
-
 #[path = "mod2a.rs"]
 mod c;