httpcaddyfile: New `handle_path` directive (#3281)

* caddyconfig: WIP implementation of handle_path

* caddyconfig: Complete the implementation - h.NewRoute was key

* caddyconfig: Add handle_path integration test

* caddyhttp: Use the path matcher as-is, strip the trailing *, update test

4 files changed, 186 insertions, 59 deletions

diff --git a/caddyconfig/httpcaddyfile/builtins.go b/caddyconfig/httpcaddyfile/builtins.go
index 2bb9b90..7026dfe 100644
--- a/caddyconfig/httpcaddyfile/builtins.go
+++ b/caddyconfig/httpcaddyfile/builtins.go
@@ -442,11 +442,11 @@ func parseRoute(h Helper) (caddyhttp.MiddlewareHandler, error) {
 }
 
 func parseHandle(h Helper) (caddyhttp.MiddlewareHandler, error) {
-	return parseSegmentAsSubroute(h)
+	return ParseSegmentAsSubroute(h)
 }
 
 func parseHandleErrors(h Helper) ([]ConfigValue, error) {
-	subroute, err := parseSegmentAsSubroute(h)
+	subroute, err := ParseSegmentAsSubroute(h)
 	if err != nil {
 		return nil, err
 	}
diff --git a/caddyconfig/httpcaddyfile/directives.go b/caddyconfig/httpcaddyfile/directives.go
index 1578772..cde9743 100644
--- a/caddyconfig/httpcaddyfile/directives.go
+++ b/caddyconfig/httpcaddyfile/directives.go
@@ -57,6 +57,7 @@ var directiveOrder = []string{
 	// special routing directives
 	"handle",
 	"route",
+	"handle_path",
 
 	// handlers that typically respond to requests
 	"respond",
@@ -261,6 +262,63 @@ func (h Helper) NewBindAddresses(addrs []string) []ConfigValue {
 	return []ConfigValue{{Class: "bind", Value: addrs}}
 }
 
+// ParseSegmentAsSubroute parses the segment such that its subdirectives
+// are themselves treated as directives, from which a subroute is built
+// and returned.
+func ParseSegmentAsSubroute(h Helper) (caddyhttp.MiddlewareHandler, error) {
+	var allResults []ConfigValue
+
+	for h.Next() {
+		// slice the linear list of tokens into top-level segments
+		var segments []caddyfile.Segment
+		for nesting := h.Nesting(); h.NextBlock(nesting); {
+			segments = append(segments, h.NextSegment())
+		}
+
+		// copy existing matcher definitions so we can augment
+		// new ones that are defined only in this scope
+		matcherDefs := make(map[string]caddy.ModuleMap, len(h.matcherDefs))
+		for key, val := range h.matcherDefs {
+			matcherDefs[key] = val
+		}
+
+		// find and extract any embedded matcher definitions in this scope
+		for i, seg := range segments {
+			if strings.HasPrefix(seg.Directive(), matcherPrefix) {
+				err := parseMatcherDefinitions(caddyfile.NewDispenser(seg), matcherDefs)
+				if err != nil {
+					return nil, err
+				}
+				segments = append(segments[:i], segments[i+1:]...)
+			}
+		}
+
+		// with matchers ready to go, evaluate each directive's segment
+		for _, seg := range segments {
+			dir := seg.Directive()
+			dirFunc, ok := registeredDirectives[dir]
+			if !ok {
+				return nil, h.Errf("unrecognized directive: %s", dir)
+			}
+
+			subHelper := h
+			subHelper.Dispenser = caddyfile.NewDispenser(seg)
+			subHelper.matcherDefs = matcherDefs
+
+			results, err := dirFunc(subHelper)
+			if err != nil {
+				return nil, h.Errf("parsing caddyfile tokens for '%s': %v", dir, err)
+			}
+			for _, result := range results {
+				result.directive = dir
+				allResults = append(allResults, result)
+			}
+		}
+	}
+
+	return buildSubroute(allResults, h.groupCounter)
+}
+
 // ConfigValue represents a value to be added to the final
 // configuration, or a value to be consulted when building
 // the final configuration.
@@ -329,63 +387,6 @@ func sortRoutes(routes []ConfigValue) {
 	})
 }
 
-// parseSegmentAsSubroute parses the segment such that its subdirectives
-// are themselves treated as directives, from which a subroute is built
-// and returned.
-func parseSegmentAsSubroute(h Helper) (caddyhttp.MiddlewareHandler, error) {
-	var allResults []ConfigValue
-
-	for h.Next() {
-		// slice the linear list of tokens into top-level segments
-		var segments []caddyfile.Segment
-		for nesting := h.Nesting(); h.NextBlock(nesting); {
-			segments = append(segments, h.NextSegment())
-		}
-
-		// copy existing matcher definitions so we can augment
-		// new ones that are defined only in this scope
-		matcherDefs := make(map[string]caddy.ModuleMap, len(h.matcherDefs))
-		for key, val := range h.matcherDefs {
-			matcherDefs[key] = val
-		}
-
-		// find and extract any embedded matcher definitions in this scope
-		for i, seg := range segments {
-			if strings.HasPrefix(seg.Directive(), matcherPrefix) {
-				err := parseMatcherDefinitions(caddyfile.NewDispenser(seg), matcherDefs)
-				if err != nil {
-					return nil, err
-				}
-				segments = append(segments[:i], segments[i+1:]...)
-			}
-		}
-
-		// with matchers ready to go, evaluate each directive's segment
-		for _, seg := range segments {
-			dir := seg.Directive()
-			dirFunc, ok := registeredDirectives[dir]
-			if !ok {
-				return nil, h.Errf("unrecognized directive: %s", dir)
-			}
-
-			subHelper := h
-			subHelper.Dispenser = caddyfile.NewDispenser(seg)
-			subHelper.matcherDefs = matcherDefs
-
-			results, err := dirFunc(subHelper)
-			if err != nil {
-				return nil, h.Errf("parsing caddyfile tokens for '%s': %v", dir, err)
-			}
-			for _, result := range results {
-				result.directive = dir
-				allResults = append(allResults, result)
-			}
-		}
-	}
-
-	return buildSubroute(allResults, h.groupCounter)
-}
-
 // serverBlock pairs a Caddyfile server block with
 // a "pile" of config values, keyed by class name,
 // as well as its parsed keys for convenience.
diff --git a/caddytest/integration/caddyfile_adapt/handle_path.txt b/caddytest/integration/caddyfile_adapt/handle_path.txt
new file mode 100644
index 0000000..7f40fcf
--- /dev/null
+++ b/caddytest/integration/caddyfile_adapt/handle_path.txt
@@ -0,0 +1,52 @@
+:80

+handle_path /api/v1/* {

+	respond "API v1"

+}

+----------

+{

+	"apps": {

+		"http": {

+			"servers": {

+				"srv0": {

+					"listen": [

+						":80"

+					],

+					"routes": [

+						{

+							"match": [

+								{

+									"path": [

+										"/api/v1/*"

+									]

+								}

+							],

+							"handle": [

+								{

+									"handler": "subroute",

+									"routes": [

+										{

+											"handle": [

+												{

+													"handler": "rewrite",

+													"strip_path_prefix": "/api/v1"

+												}

+											]

+										},

+										{

+											"handle": [

+												{

+													"body": "API v1",

+													"handler": "static_response"

+												}

+											]

+										}

+									]

+								}

+							]

+						}

+					]

+				}

+			}

+		}

+	}

+}
\ No newline at end of file
diff --git a/modules/caddyhttp/rewrite/caddyfile.go b/modules/caddyhttp/rewrite/caddyfile.go
index ee7dd23..950119d 100644
--- a/modules/caddyhttp/rewrite/caddyfile.go
+++ b/modules/caddyhttp/rewrite/caddyfile.go
@@ -15,9 +15,12 @@
 package rewrite
 
 import (
+	"encoding/json"
 	"strconv"
 	"strings"
 
+	"github.com/caddyserver/caddy/v2"
+	"github.com/caddyserver/caddy/v2/caddyconfig"
 	"github.com/caddyserver/caddy/v2/caddyconfig/httpcaddyfile"
 	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
 )
@@ -25,6 +28,7 @@ import (
 func init() {
 	httpcaddyfile.RegisterHandlerDirective("rewrite", parseCaddyfileRewrite)
 	httpcaddyfile.RegisterHandlerDirective("uri", parseCaddyfileURI)
+	httpcaddyfile.RegisterDirective("handle_path", parseCaddyfileHandlePath)
 }
 
 // parseCaddyfileRewrite sets up a basic rewrite handler from Caddyfile tokens. Syntax:
@@ -110,3 +114,73 @@ func parseCaddyfileURI(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, err
 	}
 	return rewr, nil
 }
+
+// parseCaddyfileHandlePath parses the handle_path directive. Syntax:
+//
+//     handle_path [<matcher>] {
+//         <directives...>
+//     }
+//
+// Only path matchers (with a `/` prefix) are supported as this is a shortcut
+// for the handle directive with a strip_prefix rewrite.
+func parseCaddyfileHandlePath(h httpcaddyfile.Helper) ([]httpcaddyfile.ConfigValue, error) {
+	if !h.Next() {
+		return nil, h.ArgErr()
+	}
+	if !h.NextArg() {
+		return nil, h.ArgErr()
+	}
+
+	// read the prefix to strip
+	path := h.Val()
+	if !strings.HasPrefix(path, "/") {
+		return nil, h.Errf("path matcher must begin with '/', got %s", path)
+	}
+
+	// we only want to strip what comes before the '/' if
+	// the user specified it (e.g. /api/* should only strip /api)
+	var stripPath string
+	if strings.HasSuffix(path, "/*") {
+		stripPath = path[:len(path)-2]
+	} else if strings.HasSuffix(path, "*") {
+		stripPath = path[:len(path)-1]
+	} else {
+		stripPath = path
+	}
+
+	// the ParseSegmentAsSubroute function expects the cursor
+	// to be at the token just before the block opening,
+	// so we need to rewind because we already read past it
+	h.Reset()
+	h.Next()
+
+	// parse the block contents as a subroute handler
+	handler, err := httpcaddyfile.ParseSegmentAsSubroute(h)
+	if err != nil {
+		return nil, err
+	}
+	subroute, ok := handler.(*caddyhttp.Subroute)
+	if !ok {
+		return nil, h.Errf("segment was not parsed as a subroute")
+	}
+
+	// make a matcher on the path and everything below it
+	pathMatcher := caddy.ModuleMap{
+		"path": h.JSON(caddyhttp.MatchPath{path}),
+	}
+
+	// build a route with a rewrite handler to strip the path prefix
+	route := caddyhttp.Route{
+		HandlersRaw: []json.RawMessage{
+			caddyconfig.JSONModuleObject(Rewrite{
+				StripPathPrefix: stripPath,
+			}, "handler", "rewrite", nil),
+		},
+	}
+
+	// prepend the route to the subroute
+	subroute.Routes = append([]caddyhttp.Route{route}, subroute.Routes...)
+
+	// build and return a route from the subroute
+	return h.NewRoute(pathMatcher, subroute), nil
+}