Merge pull request rust-lang#2971 from topecongiro/issue-2969

Use span_ends_with_comma to find a trailing comma in an attribute

Author: nrc

src/attr.rs

@@ -217,11 +217,8 @@ impl Rewrite for ast::MetaItem {
             ast::MetaItemKind::List(ref list) => {
                 let path = rewrite_path(context, PathContext::Type, None, &self.ident, shape)?;
 
-                let snippet = context.snippet(self.span);
-                // 2 = )] (this might go wrong if there is whitespace between the brackets, but
-                // it's close enough).
-                let snippet = snippet[..snippet.len() - 2].trim();
-                let trailing_comma = if snippet.ends_with(',') { "," } else { "" };
+                let has_comma = ::expr::span_ends_with_comma(context, self.span);
+                let trailing_comma = if has_comma { "," } else { "" };
                 let combine = list.len() == 1 && match list[0].node {
                     ast::NestedMetaItemKind::Literal(..) => false,
                     ast::NestedMetaItemKind::MetaItem(ref inner_meta_item) => {

tests/source/attrib.rs

@@ -190,3 +190,23 @@ pub struct Params {
   job: Option<Job>
 }
 }
+
+// #2969
+#[cfg(not(all(feature="std",
+              any(target_os = "linux", target_os = "android",
+                  target_os = "netbsd",
+                  target_os = "dragonfly",
+                  target_os = "haiku",
+                  target_os = "emscripten",
+                  target_os = "solaris",
+                  target_os = "cloudabi",
+                  target_os = "macos", target_os = "ios",
+                  target_os = "freebsd",
+                  target_os = "openbsd", target_os = "bitrig",
+                  target_os = "redox",
+                  target_os = "fuchsia",
+                  windows,
+                  all(target_arch = "wasm32", feature = "stdweb"),
+                  all(target_arch = "wasm32", feature = "wasm-bindgen"),
+              ))))]
+type Os = NoSource;

tests/target/attrib.rs

@@ -219,3 +219,29 @@ mod issue_2620 {
         job: Option<Job>,
     }
 }
+
+// #2969
+#[cfg(not(all(
+    feature = "std",
+    any(
+        target_os = "linux",
+        target_os = "android",
+        target_os = "netbsd",
+        target_os = "dragonfly",
+        target_os = "haiku",
+        target_os = "emscripten",
+        target_os = "solaris",
+        target_os = "cloudabi",
+        target_os = "macos",
+        target_os = "ios",
+        target_os = "freebsd",
+        target_os = "openbsd",
+        target_os = "bitrig",
+        target_os = "redox",
+        target_os = "fuchsia",
+        windows,
+        all(target_arch = "wasm32", feature = "stdweb"),
+        all(target_arch = "wasm32", feature = "wasm-bindgen"),
+    )
+)))]
+type Os = NoSource;