httpcaddyfile: Prevent rewrite routes from consolidating (fix #3108)

It's hard to say whether this was actually a bug, but the linked issue
shows why the old behavior was confusing. Basically, we infer that a
rewrite handler is supposed to act as an internal redirect, which likely
means it will no longer match the matcher(s) it did before the rewrite.

So if the rewrite directive shares a matcher with any adjacent route or
directive, it can be confusing/misleading if we consolidate the rewrite
into the same route as the next handler, which shouldn't (probably) match
after the rewrite is complete.

This is kiiiind of a hacky workaround to a quirky problem.

For edge cases like these, it is probably "cleaner" to just use handle
blocks instead, to group handlers under the same matcher, nginx-style.

1 files changed, 10 insertions, 2 deletions

diff --git a/caddyconfig/httpcaddyfile/httptype.go b/caddyconfig/httpcaddyfile/httptype.go
index 18dd0a0..473aee3 100644
--- a/caddyconfig/httpcaddyfile/httptype.go
+++ b/caddyconfig/httpcaddyfile/httptype.go
@@ -618,7 +618,16 @@ func buildSubroute(routes []ConfigValue, groupCounter counter) (*caddyhttp.Subro
 			}
 		}
 		// if there is more than one, put them in a group
-		if info.count > 1 {
+		// (special case: "rewrite" directive must always be in
+		// its own group--even if there is only one--because we
+		// do not want a rewrite to be consolidated into other
+		// adjacent routes that happen to have the same matcher,
+		// see caddyserver/caddy#3108 - because the implied
+		// intent of rewrite is to do an internal redirect,
+		// we can't assume that the request will continue to
+		// match the same matcher; anyway, giving a route a
+		// unique group name should keep it from consolidating)
+		if info.count > 1 || meDir == "rewrite" {
 			info.groupName = groupCounter.nextGroup()
 		}
 	}
@@ -662,7 +671,6 @@ func buildSubroute(routes []ConfigValue, groupCounter counter) (*caddyhttp.Subro
 // consolidateRoutes combines routes with the same properties
 // (same matchers, same Terminal and Group settings) for a
 // cleaner overall output.
-// FIXME: See caddyserver/caddy#3108
 func consolidateRoutes(routes caddyhttp.RouteList) caddyhttp.RouteList {
 	for i := 0; i < len(routes)-1; i++ {
 		if reflect.DeepEqual(routes[i].MatcherSetsRaw, routes[i+1].MatcherSetsRaw) &&