Specify the results of the discussion on parenthesis nesting: extra parentheses should be allowed.

Author: dbaron

css3-conditional/Overview.html

@@ -17,14 +17,14 @@
 
    <h1>CSS Conditional Rules Module Level 3</h1>
 
-   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 24 November
+   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 25 November
     2011</h2>
 
    <dl>
     <dt>This version:
 
-    <dd><a href="http://www.w3.org/TR/2011/ED-css3-conditional-20111124/">
-     http://www.w3.org/TR/2011/ED-css3-conditional-20111124/</a>
+    <dd><a href="http://www.w3.org/TR/2011/ED-css3-conditional-20111125/">
+     http://www.w3.org/TR/2011/ED-css3-conditional-20111125/</a>
 
     <dt>Latest version:
 
@@ -564,7 +564,11 @@ <h2 id=at-supports><span class=secno>6. </span>Feature queries: the
 
 supports_condition
   : supports_negation | supports_conjunction | supports_disjunction |
-    supports_declaration_condition
+    supports_condition_in_parens
+  ;
+
+supports_condition_in_parens
+  : ( '(' supports_condition ')' S* ) | supports_declaration_condition
   ;
 
 supports_negation
@@ -579,10 +583,6 @@ <h2 id=at-supports><span class=secno>6. </span>Feature queries: the
   : supports_condition_in_parens ( 'or' S* supports_condition_in_parens )+
   ;
 
-supports_condition_in_parens
-  : ( '(' supports_condition ')' S* ) | supports_declaration_condition
-  ;
-
 supports_declaration_condition
   : '(' S* core_declaration ')' S*
   ;</pre>
@@ -598,16 +598,6 @@ <h2 id=at-supports><span class=secno>6. </span>Feature queries: the
    not</strong> use such a rule and processors <strong>must</strong> ignore
    such a rule.
 
-  <p class=issue>The grammar above attempted to prevent nesting of extra
-   parentheses; however, discussion in the working group has led to the
-   conclusion that this was a bad idea, and therefore it should be changed to
-   allow arbitrary nesting of extra parentheses (which, for example, makes it
-   easier to comment things out). There was also discussion of allowing the
-   toplevel parentheses around a declaration to be omitted, though opinion
-   tended towards thinking this was a bad idea. See <a
-   href="http://lists.w3.org/Archives/Public/www-style/2011Aug/thread.html#msg247">thread</a>
-   on www-style.
-
   <p class=note>Note that this means that declarations that meet the
    forward-compatible syntax for declarations are permitted (and support for
    them is then tested by the &lsquo;<code class=css>@supports</code>&rsquo;
@@ -629,6 +619,12 @@ <h2 id=at-supports><span class=secno>6. </span>Feature queries: the
 
    <dd> The result is the result of the single child term.
 
+   <dt>supports_condition_in_parens
+
+   <dd> The result is the result of the single
+    <code>supports_condition</code> or
+    <code>supports_declaration_condition</code> child term.
+
    <dt>supports_negation
 
    <dd> The result is the <em>negation</em> of the result of the
@@ -646,12 +642,6 @@ <h2 id=at-supports><span class=secno>6. </span>Feature queries: the
     <code>supports_condition_in_parens</code> child terms is true; otherwise
     it is false.
 
-   <dt>supports_condition_in_parens
-
-   <dd> The result is the result of the single
-    <code>supports_condition</code> or
-    <code>supports_declaration_condition</code> child term.
-
    <dt>supports_declaration_condition
 
    <dd> The result is whether the CSS processor <a
@@ -751,6 +741,37 @@ <h2 id=at-supports><span class=secno>6. </span>Feature queries: the
 }</pre>
   </div>
 
+  <p>The declaration being tested must always occur within parentheses, when
+   it is the only thing in the expression.
+
+  <p>
+
+  <div class=example>
+   <p>For example, the following rule is not valid:
+
+   <pre class=illegal-example>@supports display: flexbox {
+  // ...
+}</pre>
+
+   <p>Instead, authors must write:</p>
+
+   <pre>@supports (display: flexbox) {
+  // ...
+}</pre>
+  </div>
+
+  <p>The syntax allows extra parentheses when they are not needed. This
+   flexibility is sometimes useful for authors (for example, when commenting
+   out parts of an expression) and may also be useful for authoring tools.
+
+  <div class=example>
+   <p>For example, authors may write:</p>
+
+   <pre>@supports ((display: flexbox)) {
+  // ...
+}</pre>
+  </div>
+
   <h3 id=support-definition><span class=secno>6.1. </span>Definition of
    support</h3>
 

css3-conditional/Overview.src.html

@@ -377,7 +377,11 @@ <h2 id="at-supports">Feature queries: the '@supports' rule</h2>
 
 supports_condition
   : supports_negation | supports_conjunction | supports_disjunction |
-    supports_declaration_condition
+    supports_condition_in_parens
+  ;
+
+supports_condition_in_parens
+  : ( '(' supports_condition ')' S* ) | supports_declaration_condition
   ;
 
 supports_negation
@@ -392,10 +396,6 @@ <h2 id="at-supports">Feature queries: the '@supports' rule</h2>
   : supports_condition_in_parens ( 'or' S* supports_condition_in_parens )+
   ;
 
-supports_condition_in_parens
-  : ( '(' supports_condition ')' S* ) | supports_declaration_condition
-  ;
-
 supports_declaration_condition
   : '(' S* core_declaration ')' S*
   ;</pre>
@@ -408,16 +408,6 @@ <h2 id="at-supports">Feature queries: the '@supports' rule</h2>
 above is invalid.  Style sheets <strong>must not</strong> use such a
 rule and processors <strong>must</strong> ignore such a rule.</p>
 
-<p class="issue">The grammar above attempted to prevent nesting of extra
-parentheses; however, discussion in the working group has led to the
-conclusion that this was a bad idea, and therefore it should be changed
-to allow arbitrary nesting of extra parentheses (which, for example,
-makes it easier to comment things out).  There was also discussion of
-allowing the toplevel parentheses around a declaration to be omitted,
-though opinion tended towards thinking this was a bad idea.  See
-<a href="http://lists.w3.org/Archives/Public/www-style/2011Aug/thread.html#msg247">thread</a>
-on www-style.</p>
-
 <p class="note">Note that this means that declarations that meet the
 forward-compatible syntax for declarations are permitted (and support
 for them is then tested by the ''@supports'' rule), but declarations
@@ -438,6 +428,12 @@ <h2 id="at-supports">Feature queries: the '@supports' rule</h2>
   The result is the result of the single child term.
 </dd>
 
+<dt>supports_condition_in_parens</dt>
+<dd>
+  The result is the result of the single <code>supports_condition</code>
+  or <code>supports_declaration_condition</code> child term.
+</dd>
+
 <dt>supports_negation</dt>
 <dd>
   The result is the <em>negation</em> of the result of the
@@ -458,12 +454,6 @@ <h2 id="at-supports">Feature queries: the '@supports' rule</h2>
   otherwise it is false.
 </dd>
 
-<dt>supports_condition_in_parens</dt>
-<dd>
-  The result is the result of the single <code>supports_condition</code>
-  or <code>supports_declaration_condition</code> child term.
-</dd>
-
 <dt>supports_declaration_condition</dt>
 <dd>
   The result is whether the CSS processor <a
@@ -545,6 +535,32 @@ <h2 id="at-supports">Feature queries: the '@supports' rule</h2>
 }</pre>
 </div>
 
+<p>The declaration being tested must always occur within parentheses,
+when it is the only thing in the expression.<p>
+
+<div class="example">
+<p>For example, the following rule is not valid:
+<pre class="illegal-example">@supports display: flexbox {
+  // ...
+}</pre>
+<p>Instead, authors must write:</p>
+<pre>@supports (display: flexbox) {
+  // ...
+}</pre>
+</div>
+
+<p>The syntax allows extra parentheses when they are not needed.  This
+flexibility is sometimes useful for authors (for example, when
+commenting out parts of an expression) and may also be useful for
+authoring tools.</p>
+
+<div class="example">
+<p>For example, authors may write:</p>
+<pre>@supports ((display: flexbox)) {
+  // ...
+}</pre>
+</div>
+
 <h3 id="support-definition">Definition of support</h3>
 
 <p>A CSS processor is considered to <dfn id="dfn-support">support</dfn>