refactor how newlines are emitted

still not perfect, but getting closer. this brings the bulma diff down
from around 1,700 lines to only 500 (all a result of newlines)

src/lib.rs

@@ -160,7 +160,7 @@ pub fn from_path(p: &str) -> Result<String> {
     .parse()
     .map_err(|e| raw_to_parse_error(&map, *e))?;
 
-    Css::from_stmts(stmts)
+    Css::from_stmts(stmts, false)
         .map_err(|e| raw_to_parse_error(&map, *e))?
         .pretty_print(&map)
         .map_err(|e| raw_to_parse_error(&map, *e))
@@ -205,7 +205,7 @@ pub fn from_string(p: String) -> Result<String> {
     .parse()
     .map_err(|e| raw_to_parse_error(&map, *e))?;
 
-    Css::from_stmts(stmts)
+    Css::from_stmts(stmts, false)
         .map_err(|e| raw_to_parse_error(&map, *e))?
         .pretty_print(&map)
         .map_err(|e| raw_to_parse_error(&map, *e))
@@ -241,7 +241,7 @@ pub fn from_string(p: String) -> std::result::Result<String, JsValue> {
     .parse()
     .map_err(|e| raw_to_parse_error(&map, *e).to_string())?;
 
-    Ok(Css::from_stmts(stmts)
+    Ok(Css::from_stmts(stmts, false)
         .map_err(|e| raw_to_parse_error(&map, *e).to_string())?
         .pretty_print(&map)
         .map_err(|e| raw_to_parse_error(&map, *e).to_string())?)

src/output.rs

@@ -82,15 +82,19 @@ impl Toplevel {
 #[derive(Debug, Clone)]
 pub(crate) struct Css {
     blocks: Vec<Toplevel>,
+    in_at_rule: bool,
 }
 
 impl Css {
-    pub const fn new() -> Self {
-        Css { blocks: Vec::new() }
+    pub const fn new(in_at_rule: bool) -> Self {
+        Css {
+            blocks: Vec::new(),
+            in_at_rule,
+        }
     }
 
-    pub(crate) fn from_stmts(s: Vec<Stmt>) -> SassResult<Self> {
-        Css::new().parse_stylesheet(s)
+    pub(crate) fn from_stmts(s: Vec<Stmt>, in_at_rule: bool) -> SassResult<Self> {
+        Css::new(in_at_rule).parse_stylesheet(s)
     }
 
     fn parse_stmt(&mut self, stmt: Stmt) -> SassResult<Vec<Toplevel>> {
@@ -232,7 +236,7 @@ impl Css {
                         continue;
                     }
                     has_written = true;
-                    if should_emit_newline {
+                    if should_emit_newline && !self.in_at_rule {
                         should_emit_newline = false;
                         writeln!(buf)?;
                     }
@@ -247,10 +251,7 @@ impl Css {
                         continue;
                     }
                     has_written = true;
-                    if should_emit_newline {
-                        should_emit_newline = false;
-                        writeln!(buf)?;
-                    }
+
                     writeln!(
                         buf,
                         "{}{} {{",
@@ -290,7 +291,7 @@ impl Css {
                         writeln!(buf, " {{")?;
                     }
 
-                    Css::from_stmts(body)?._inner_pretty_print(buf, map, nesting + 1)?;
+                    Css::from_stmts(body, true)?._inner_pretty_print(buf, map, nesting + 1)?;
                     writeln!(buf, "{}}}", padding)?;
                 }
                 Toplevel::Keyframes(k) => {
@@ -313,7 +314,7 @@ impl Css {
                         writeln!(buf, " {{")?;
                     }
 
-                    Css::from_stmts(body)?._inner_pretty_print(buf, map, nesting + 1)?;
+                    Css::from_stmts(body, true)?._inner_pretty_print(buf, map, nesting + 1)?;
                     writeln!(buf, "{}}}", padding)?;
                 }
                 Toplevel::Supports { params, body } => {
@@ -335,19 +336,16 @@ impl Css {
                         writeln!(buf, " {{")?;
                     }
 
-                    Css::from_stmts(body)?._inner_pretty_print(buf, map, nesting + 1)?;
+                    Css::from_stmts(body, true)?._inner_pretty_print(buf, map, nesting + 1)?;
                     writeln!(buf, "{}}}", padding)?;
                 }
                 Toplevel::Media { query, body } => {
                     if body.is_empty() {
                         continue;
                     }
-                    if should_emit_newline {
-                        should_emit_newline = false;
-                        writeln!(buf)?;
-                    }
+
                     writeln!(buf, "{}@media {} {{", padding, query)?;
-                    Css::from_stmts(body)?._inner_pretty_print(buf, map, nesting + 1)?;
+                    Css::from_stmts(body, true)?._inner_pretty_print(buf, map, nesting + 1)?;
                     writeln!(buf, "{}}}", padding)?;
                 }
                 Toplevel::Style(s) => {

tests/keyframes.rs

@@ -109,3 +109,15 @@ test!(
     "@keyframes foo {/**/}",
     "@keyframes foo {\n  /**/\n}\n"
 );
+test!(
+    keyframes_multiple_rulesets,
+    "@keyframes {
+        to {
+            color: red;
+        }
+        from {
+            color: green;
+        }
+    }",
+    "@keyframes {\n  to {\n    color: red;\n  }\n  from {\n    color: green;\n  }\n}\n"
+);

tests/media.rs

@@ -17,3 +17,17 @@ test!(
     "@media foo {\n  a {\n    color: red;\n  }\n}\n"
 );
 test!(empty_body, "@media (min-width: 2px) {}", "");
+test!(
+    newlines_are_not_emitted_for_child_styles,
+    "a {
+        @media screen {
+            b {
+                color: red;
+            }
+            c {
+                color: green;
+            }
+        }
+    }",
+    "@media screen {\n  a b {\n    color: red;\n  }\n  a c {\n    color: green;\n  }\n}\n"
+);