[css-navigation-1] Initial draft of a simpler alternative to navigation-param().

This is a first draft of attempting to replace navigation-param() with a
simpler syntax that allows just a 3x4 space of alternatives: 3 matching
types (that replace navigation-param()) and 4 match targets (which are
actually a new feature relative to navigation-param()).

This is a start to addressing the feedback in #13163 (but I expect
further changes before the draft is ready for another round of review).

Author: dbaron

css-navigation-1/Overview.bs

@@ -393,10 +393,14 @@ by matching the relevant parts of the navigation URL to the link URL.
   navigation: auto;
 }
 
-@route --movie-details {
+@route --movie-details-with-id {
   /* match URLs like /en/movie/123 which is the English page
-     about a movie with ID 123 */
-  pattern: url-pattern("/:lang/movie/:id");
+     about a movie with ID 123.  Be careful to specify the
+     language part with a "*" but the ID part with a named
+     :id parameter so that matching using the 'match-params'
+     keyword (the default) will require equal IDs but allow
+     differences of language. */
+  pattern: url-pattern("/*/movie/:id");
 }
 
 /* capture the overall area representing the movie, and a
@@ -407,19 +411,20 @@ by matching the relevant parts of the navigation URL to the link URL.
    movie we are currently navigating to or from.  (lang can
    be different, though.)
 
-   Just :link-to(--movie-details) requires that the target
-   of the link match the URL pattern defined by the "@route
-   --movie-details" rule.
+   This depends on the --movie-details-with-id route
+   declaring the ID but not the language with a named
+   parameter, and the use of match-params(navigation-other).
 
-   The navigation-param(id) further requires that either the
-   from or the to URL of the current navigation also match
-   the URL pattern represented by the "@route
-   --movie-details" rule, and that that the 'id' named group
-   from that match be the same as the 'id' named group from
-   the match with the link's target.
+   This means that both the of the link and the other URL of
+   the current navigation match the URL pattern defined by
+   the "@route --movie-details-with-id" rule, and that the
+   id named group from both matches be the same.  (However,
+   the URLs can be different because the * part of the
+   match, containing the language, can be different.)
    */
-.movie-container:has(> .movie-title:link-to(
-  --movie-details with navigation-param(id))) {
+.movie-container:has(
+    > .movie-title:link-to(--movie-details-with-id
+                             with match-params(navigation-other))) {
 
   view-transition-name: movie-container;
 
@@ -440,24 +445,22 @@ and the pseudo-class matches any element where:
 * the target of link matches the <<link-condition>>, as defined below.
 
 <pre class="prod def" dfn-type="type" nohighlight>
-<dfn><<link-condition>></dfn> = <<link-condition-base>> [ with <<navigation-param-expression>> ]?
+<dfn><<link-condition>></dfn> = <<link-condition-base>> [ with <<navigation-match>> ]?
 <dfn><<link-condition-base>></dfn> = <<navigation-location>>
-<dfn><<navigation-param-expression>></dfn> = ( <<navigation-param-and>> ) |
-                                ( <<navigation-param-or>> ) |
-                                <<navigation-param>>
-<dfn><<navigation-param-and>></dfn> = <<navigation-param-expression>>
-                         [ "and" <<navigation-param-expression>> ]*
-<dfn><<navigation-param-or>></dfn> = <<navigation-param-expression>>
-                        [ "or" <<navigation-param-expression>> ]*
-<dfn><<navigation-param>></dfn> = <<navigation-param-key-value>> | <<navigation-param-function>>
-<dfn><<navigation-param-key-value>></dfn> = ( <<ident>> : <<string>> )
-<dfn><<navigation-param-function>></dfn> = navigation-param( <<ident>> )
+  // Note: <<navigation-match>> is defining three functions
+  // with identical syntax.
+<dfn><<navigation-match>></dfn> = <<pattern-match-type>>( <<navigation-match-target>> )
+<dfn><<pattern-match-type>></dfn> = match-pattern | match-params | match-url
+<dfn><<navigation-match-target>></dfn> = navigation-other | navigation-current |
+                            navigation-from | navigation-to
 </pre>
 
 A <<link-condition>> matches the target of the link when both:
 * the <<link-condition-base>> matches the target of the link, and
-* the <<navigation-param-expression>> matches the target of the link,
-    with the [=URL pattern=] represented by the <<link-condition-base>> as context
+* either:
+    * a <<navigation-match>> is not present, or
+    * the <<navigation-match>> matches the target of the link,
+        with the [=URL pattern=] represented by the <<link-condition-base>> as context
 
 A <<link-condition-base>> represents a [=URL pattern=].
 If the <<link-condition-base>> is a <<url-pattern()>>,
@@ -473,52 +476,59 @@ given <var>urlPattern</var> as
 the [=URL pattern=] that it represents and
 <var>input</var> as the given URL.
 
-A <<navigation-param-expression>> matches a URL
-(with a [=URL Pattern=] as context)
-based on standard boolean logic for <code>and</code> and <code>or</code>,
-and based on whether each <<navigation-param>> matches the URL
-(with the URL Pattern as context).
-
-A <<navigation-param>> matches the URL <var>input</var> (with a URL Pattern <var>urlPattern</var> as context)
+A <<navigation-match>> matches the URL <var>linkTarget</var>
+(with a URL Pattern <var>urlPattern</var> as context)
 if the following steps return true:
-1. Let <var>matchResult</var> be the result of
+1. Let <var>targetMatchResult</var> be the result of
     [=URL pattern/match|match a URL pattern=]
-    given <var>urlPattern</var> and <var>input</var>.
-    the [=URL pattern=]
-    represented by the <<url-pattern()>> function in the <<link-condition-base>>
-    (see [=create a URL pattern for url-pattern()=])
-1. If <var>matchResult</var> is null, return false.
+    given <var>urlPattern</var> and <var>linkTarget</var>.
+1. If <var>targetMatchResult</var> is null, return false.
 
     NOTE: This doesn't really matter because
     in this case the <<link-condition-base>> also doesn't match.
-1. For each property <var>prop</var> of <var>matchResult</var> (a {{URLPatternResult}})
-    that is a {{URLPatternComponentResult}}:
-    1. For each [=map/entry=] <var>entry</var> in its {{URLPatternComponentResult/groups}},
-        then:
-        1. If <<navigation-param>> is a <<navigation-param-key-value>>,
-            return true if
-            <var>entry</var>'s [=map/key=] is the <<ident>>
-            and <var>entry</var>'s [=map/value=] is the <<string>>.
-        1. If <<navigation-param>> is a <<navigation-param-function>>,
-            and <var>entry</var>'s [=map/key=] is the function's <<ident>>,
-            then for each <var>navigationUrl</var> of the
-            [=current to URL=]
-            and [=current from URL=]:
-            1. Let <var>navigationMatchResult</var> be the result of
-                [=URL pattern/match|match a URL pattern=]
-                given <var>urlPattern</var> and <var>navigationUrl</var>.
-            1. If <var>navigationMatchResult</var> is null, [=continue=].
-            1. Return true if <var>navigationMatchResult</var>'s
-                property <var>prop</var>
-                has an [=map/entry=]
-                whose [=map/key=] is the same as <var>entry</var>'s key
-                and whose [=map/value=] is the same as <var>entry</var>'s value.
-
-                NOTE: This step makes the ''navigation-param()'' function
-                perform what is essentially a three-way match,
-                between the target of the link,
-                the provided URL pattern,
-                and the from or to URL of the current navigation.
+1. Let <var>matchType</var> be the <<pattern-match-type>> of the
+    <<navigation-match>>.
+1. Let <var>matchTarget</var> be the <<navigation-match-target>> argument
+    of the <<navigation-match>>.
+1. Let <var>navigationURL</var> be:
+    : If <var>matchTarget</var> is ''navigation-other'',
+    :: the <a>current other URL</a> of the document.
+    : Otherwise, if <var>matchTarget</var> is ''navigation-current'',
+    :: the <a>current URL</a> of the document.
+    : Otherwise, if <var>matchTarget</var> is ''navigation-from'',
+    :: the <a>current from URL</a> of the document.
+    : Otherwise (Assert: <var>matchTarget</var> is ''navigation-to''),
+    :: the <a>current to URL</a> of the document.
+1. If <var>navigationURL</var> is null, return false.
+1. : If <var>matchType</var> is ''match-pattern''
+    :: Return true if
+        the result of [=URL pattern/match|match a URL pattern=] given
+        <var>urlPattern</var> and <var>navigationURL</var> is not null;
+        otherwise return false.
+
+    : If <var>matchType</var> is ''match-params''
+    :: 1. Let <var>navigationMatchResult</var> be the result of
+            [=URL pattern/match|match a URL pattern=] given
+            <var>navigationURL</var> and <var>urlPattern</var>.
+
+        1. If either <var>navigationMatchResult</var> is null, return false.
+
+        1. For each property <var>prop</var> of {{URLPatternResult}} that is a
+            {{URLPatternComponentResult}}:
+
+            1. If {{URLPatternComponentResult/groups}} of <var>prop</var> of
+                <var>targetMatchResult</var> is not equal to
+                {{URLPatternComponentResult/groups}} of <var>prop</var> of
+                <var>navigationMatchResult</var>,
+                then return false.
+
+                ISSUE: Need to formally define equality of ordered maps.
+
+        1. Return true.
+
+    : If <var>matchType</var> is ''match-url''
+    :: Return true if <var>linkTarget</var> equals <var>navigationURL</var>;
+        otherwise return false.
 
 NOTE: Some of the design discussion for this feature has been in
 <a href="https://github.com/w3c/csswg-drafts/issues/13163">w3c/csswg-drafts#13163</a>.
@@ -618,6 +628,16 @@ ISSUE: The above definitions of from and to apparently don't work right
 if you start a same-document navigation (e.g., with {{History/pushState}})
 in the middle of a cross-document navigation.
 
+The <dfn>current URL</dfn> of a [=/document=] is a URL.
+It is defined as follows:
+
+1. ISSUE: Write this!
+
+The <dfn>current other URL</dfn> of a [=/document=] is a URL or null.
+It is defined as follows:
+
+1. ISSUE: Write this!
+
 The <dfn>current navigation type</dfn> of a [=/document=] is a {{NavigationType}} or null.
 It is defined as follows: