Let's assume we have a web service with prefix /foo. There are many sub-paths for /foo/.... Let's also assume we want to have different timeouts for /foo and /foo/.*.

We would expect the following to work:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: subpath-foo
  annotations:
    haproxy.org/standalone-backend: "true"
    haproxy.org/timeout-server: 5s
spec:
  ingressClassName: haproxy
  rules:
  - host: example.tld 
    http:
      paths:
      - path: /foo
        pathType: Prefix
        backend:
          service:
            name: foo-service
            port:
              name: http
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: just-foo
  annotations:
    haproxy.org/standalone-backend: "true"
    haproxy.org/timeout-server: 10s
spec:
  ingressClassName: haproxy
  rules:
  - host: example.tld 
    http:
      paths:
      - path: /foo
        pathType: Exact
        backend:
          service:
            name: foo-service
            port:
              name: http

The annotation haproxy.org/standalone-backendensures two separate backends are created so that the different timeouts do not fight each other.
Now we have the problem that /etc/haproxy/maps/path-exact.map has the following contents:

example.tld/foo          ing_default_subpath-foo_http.dbe4b28f9c4404fc36a7ae76ead9a37d
example.tld/foo          ing_default_just-foo_http.dbe4b28f9c4404fc36a7ae76ead9a37d

That means the actual exact match from ingress just-foo will never match since pathType Prefix patterns are also put into this pattern file.
Here we can find the responsible code:

	path := route.Path.Path
	switch {
	case route.Path.PathTypeMatch == store.PATH_TYPE_EXACT:
		mapFiles.MapAppend(PATH_EXACT, route.Host+path+"\t\t\t"+value)
	case path == "" || path == "/":
		mapFiles.MapAppend(PATH_PREFIX, route.Host+"/"+"\t\t\t"+value)
	case route.Path.PathTypeMatch == store.PATH_TYPE_PREFIX:
		path = strings.TrimSuffix(path, "/")
		mapFiles.MapAppend(PATH_EXACT, route.Host+path+"\t\t\t"+value)
		mapFiles.MapAppend(PATH_PREFIX, route.Host+path+"/"+"\t\t\t"+value)
	case route.Path.PathTypeMatch == store.PATH_TYPE_IMPLEMENTATION_SPECIFIC:
		path = strings.TrimSuffix(path, "/")
		mapFiles.MapAppend(PATH_EXACT, route.Host+path+"\t\t\t"+value)
		mapFiles.MapAppend(PATH_PREFIX, route.Host+path+"\t\t\t"+value)
	default:
		return fmt.Errorf("unknown path type '%s' with backend '%s'", route.Path.PathTypeMatch, route.BackendName)
	}

I do understand why Prefix paths must have an entry in path-exact.map: The definition of ingress resources mandates that /foo must match /foo and /foo/bar but never /foobar. Therefore we add /foo to exact matches and /foo/ to prefix matches (via map_beg).

The only way I see to resolve this issue in a clean and backward-compatible way is to introduce a new map file which will contain all exact matches from pathType Prefix only and it will be matched if there was no match in path-exact.map which will then contain ONLY pathType Exact patterns.

I will follow up with a PR.