1 files changed, 53 insertions, 0 deletions
diff --git a/pathrouter/here.go b/pathrouter/here.go
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--- /dev/null
+++ b/pathrouter/here.go
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+// SPDX-FileCopyrightText: 2026 Stefan Majewsky <majewsky@gmx.net>
+// SPDX-License-Identifier: Apache-2.0
+
+package pathrouter
+
+import (
+	. "go.xyrillian.de/gg/option"
+)
+
+// Here is a [Matcher] that matches effectively empty subpaths, that is:
+// subpaths that are either empty or only contain a heretofore unmatched trailing slash.
+// It can be used to opt-in to allowing trailing slashes at the ends of URL paths:
+//
+//	// only matches "/foo/bar"
+//	pr.Element("foo", pr.Element("bar", pr.Handlers(...))
+//
+//	// also matches "/foo/bar/"
+//	pr.Element("foo", pr.Element("bar", pr.Here(pr.Handlers(...)))
+//
+// The next matcher must match only the empty path, so currently only [Handlers] is allowed.
+//
+// Here is provided as a useful shorthand, but could be implemented using the other matchers like so:
+//
+//	// this...
+//	m := pr.Here(pr.Handlers(byMethod))
+//
+//	// ...is equivalent to this
+//	h := pr.Handlers(byMethod)
+//	m := pr.Choice(h, pr.Element("/", h))
+//
+// The name "Here" makes sense when Here() appears as one of several options within Choice(),
+// where the other options would match subpaths, while Here() matches, well, "here".
+// The example in the package docstring illustrates this.
+func Here(matcher Matcher) Matcher {
+	return here(matcher.downcast())
+}
+
+func here(matcher realMatcher) Matcher {
+	if matcher.minLength != 0 || matcher.maxLength != Some(0) {
+		panic("matcher within Here() must be Handlers()")
+	}
+
+	return realMatcher{
+		minLength: 0,
+		maxLength: Some(1),
+		accept: func(path []string, vars map[string]string) HandlerFunc {
+			if len(path) == 0 || (len(path) == 1 && path[0] == "") {
+				return matcher.accept(nil, vars)
+			}
+			return nil
+		},
+	}
+}