[css-navigation-1] Add :link-to() pseudo-class (with navigation-param() function). (#13134)

This adds an initial proposal for the :link-to() pseudo-class and a
navigation-param() function that goes inside of it.

This also refactors some of the invocations of the URL pattern "match"
algorithm to structure the parameters the way the algorithm expects
(and be a little bit clearer that a base URL doesn't need to be
provided).

Author: dbaron

css-navigation-1/Overview.bs

@@ -115,9 +115,11 @@ as follows:
 : <<navigation-test>>
 ::	: <<navigation-location>>
 	: at: <<navigation-location>>
-	:: The result is true if
-		the document's [=Document/URL=] [=URL pattern/match|matches=]
-		the [=navigation location URL pattern=] of <<navigation-location>>.
+	:: The result is whether the result of
+		[=URL pattern/match|match a URL pattern=] is non-null
+		given <var>urlPattern</var> as
+		the [=navigation location URL pattern=] of <<navigation-location>>,
+		<var>input</var> as the document's [=Document/URL=].
 
 	: from: <<navigation-location>>
 	:: The result is true if
@@ -127,19 +129,26 @@ as follows:
 		* its [=transition=] is non-null,
 			its [=from entry=]'s {{NavigationHistoryEntry/url}}
 			is non-null and
-			[=URL pattern/match|matches=]
-			the [=navigation location URL pattern=] of <<navigation-location>>.
+			[=URL pattern/match|match a URL pattern=] is non-null when
+			given <var>urlPattern</var> as
+			the [=navigation location URL pattern=] of <<navigation-location>>,
+			<var>input</var> as that
+			[=from entry=]'s {{NavigationHistoryEntry/url}}.
 
 			NOTE: This part handles <code>from:</code> when it matches in the old page.
 
 		* its [=activation=] is non-null,
 			the document's [=has been revealed=] is false or
 			was false at the start of the current [=task=],
 			and the activation's {{NavigationActivation/from}}'s
-			{{NavigationHistoryEntry/url}}'s
+			{{NavigationHistoryEntry/url}}
 			is non-null and
-			[=URL pattern/match|matches=]
-			the [=navigation location URL pattern=] of <<navigation-location>>.
+			[=URL pattern/match|match a URL pattern=] is non-null when
+			given <var>urlPattern</var> as
+			the [=navigation location URL pattern=] of <<navigation-location>>,
+			<var>input</var> as that
+			activation's {{NavigationActivation/from}}'s
+			{{NavigationHistoryEntry/url}}.
 
 			NOTE: This part handles <code>from:</code> when it matches in the new page.
 
@@ -149,9 +158,10 @@ as follows:
 		is non-null, and either:
 
 		* its [=ongoing navigate event=] is non-null,
-			and the [=current to url=]
-			[=URL pattern/match|matches=]
+			[=URL pattern/match|match a URL pattern=] is non-null
+			given <var>urlPattern</var> as
 			the [=navigation location URL pattern=] of <<navigation-location>>,
+			<var>input</var> as the [=current to url=],
 			where the <dfn>current to url</dfn> is defined as:
 
 			* if the {{pageswap}} event has fired since that navigation began,
@@ -188,10 +198,14 @@ as follows:
 			the document's [=has been revealed=] is false or
 			was false at the start of the current [=task=],
 			and the activation's {{NavigationActivation/entry}}'s
-			{{NavigationHistoryEntry/url}}'s
+			{{NavigationHistoryEntry/url}}
 			is non-null and
-			[=URL pattern/match|matches=]
-			the [=navigation location URL pattern=] of <<navigation-location>>.
+			[=URL pattern/match|match a URL pattern=] is non-null
+			given <var>urlPattern</var> as
+			the [=navigation location URL pattern=] of <<navigation-location>>,
+			<var>input</var> as that
+			activation's {{NavigationActivation/entry}}'s
+			{{NavigationHistoryEntry/url}}.
 
 			NOTE: This part handles <code>to:</code> when it matches in the new page.
 
@@ -266,7 +280,98 @@ to model it after.
 
 <h2 id="link-navigation-pseudo-classes">Pseudo-classes for navigation-related links</h2>
 
-TODO: To be written.
+This specification defines a new '':link-to()'' functional pseudo-class
+that matches link elements that link to a certain URL.
+
+The '':link-to()'' pseudo-class takes a single argument, a <<link-condition>>,
+and the pseudo-class matches any element where:
+* the element matches '':any-link''
+* 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-base>></dfn> = <<url-pattern()>>
+<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>> )
+</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
+
+A <<link-condition-base>> represents a [=URL pattern=].
+If the <<link-condition-base>> is a <<url-pattern()>>,
+then it represents the URL pattern
+represented by the <<url-pattern()>> function
+(see [=create a URL pattern for url-pattern()=]).
+
+A <<link-condition-base>> matches a URL
+when [=URL pattern/match|match a URL pattern=] is non-null
+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)
+if the following steps return true:
+1. Let <var>matchResult</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.
+
+	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
+			<span class="issue">extract "current to URL" and
+			"current from URL" from ''@navigation''
+			definitions above and link to them</span>:
+			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.
+
+ISSUE: A <<link-condition>> should also be able to be a named route
+once those are added back to the spec.
 
 <h2 id="url-pattern-function">The ''url-pattern()'' function</h2>