refactor(routing): drop predicate dep, parse matcher rules via go/ast

Replace the vulcand/predicate dependency in the routing rules parser with a
direct go/parser/go/ast implementation covering the same grammar (matcher
calls, parentheses, &&/||/!). This removes the predicate -> gravitational/
trace -> logrus logging chain from x, since trace was only used to build
errors. Public API (NewParser, Parser, TreeBuilder, Parse, CheckRule,
ParseMatchers) is unchanged and the existing test suite passes as-is.

go.mod

@@ -43,7 +43,6 @@ require (
 	github.com/tidwall/sjson v1.2.5
 	github.com/vishvananda/netlink v1.1.1-0.20211118161826-650dca95af54
 	github.com/vishvananda/netns v0.0.4
-	github.com/vulcand/predicate v1.2.0
 	github.com/xjasonlyu/tun2socks/v2 v2.6.0
 	github.com/xtaci/kcp-go/v5 v5.6.5
 	github.com/xtaci/smux v1.5.31
@@ -71,7 +70,6 @@ require (
 	github.com/lufia/plan9stats v0.0.0-20211012122336-39d0f177ccd0 // indirect
 	github.com/power-devops/perfstat v0.0.0-20210106213030-5aafc221ea8c // indirect
 	github.com/shoenig/go-m1cpu v0.1.6 // indirect
-	github.com/sirupsen/logrus v1.9.3 // indirect
 	github.com/tidwall/match v1.1.1 // indirect
 	github.com/tidwall/pretty v1.2.0 // indirect
 	github.com/tklauser/go-sysconf v0.3.12 // indirect
@@ -102,9 +100,7 @@ require (
 	github.com/godbus/dbus/v5 v5.1.0 // indirect
 	github.com/google/btree v1.1.3 // indirect
 	github.com/google/gopacket v1.1.19 // indirect
-	github.com/gravitational/trace v1.1.16-0.20220114165159-14a9a7dd6aaf // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
-	github.com/jonboulle/clockwork v0.2.2 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/klauspost/cpuid/v2 v2.3.0 // indirect
 	github.com/klauspost/reedsolomon v1.11.8 // indirect
@@ -142,7 +138,6 @@ require (
 	golang.org/x/arch v0.22.0 // indirect
 	golang.org/x/mod v0.37.0 // indirect
 	golang.org/x/sync v0.22.0
-	golang.org/x/term v0.45.0 // indirect
 	golang.org/x/tools v0.47.0 // indirect
 	golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260723215102-3fe39f3c1018 // indirect

go.sum

@@ -36,7 +36,6 @@ github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cu
 github.com/dunglas/httpsfv v1.1.0 h1:Jw76nAyKWKZKFrpMMcL76y35tOpYHqQPzHQiwDvpe54=
 github.com/dunglas/httpsfv v1.1.0/go.mod h1:zID2mqw9mFsnt7YC3vYQ9/cjq30q41W+1AnDwH8TiMg=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
-github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1mIlRU8Am5FuJP05cCM98=
 github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
 github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHkI4W8=
@@ -124,14 +123,10 @@ github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/gorilla/websocket v1.5.3 h1:saDtZ6Pbx/0u+bgYQ3q96pZgCzfhKXGPqt7kZ72aNNg=
 github.com/gorilla/websocket v1.5.3/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
-github.com/gravitational/trace v1.1.16-0.20220114165159-14a9a7dd6aaf h1:C1GPyPJrOlJlIrcaBBiBpDsqZena2Ks8spa5xZqr1XQ=
-github.com/gravitational/trace v1.1.16-0.20220114165159-14a9a7dd6aaf/go.mod h1:zXqxTI6jXDdKnlf8s+nT+3c8LrwUEy3yNpO4XJL90lA=
 github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
 github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
 github.com/hashicorp/yamux v0.1.1 h1:yrQxtgseBDrq9Y652vSRDvsKCJKOUD+GzTS4Y0Y8pvE=
 github.com/hashicorp/yamux v0.1.1/go.mod h1:CtWFDAQgb7dxtzFs4tWbplKIe2jSi3+5vKbgIO0SLnQ=
-github.com/jonboulle/clockwork v0.2.2 h1:UOGuzwb1PwsrDAObMuhUnj0p5ULPj8V/xJ7Kx9qUBdQ=
-github.com/jonboulle/clockwork v0.2.2/go.mod h1:Pkfl5aHPm1nk2H9h0bjmnJD/BcgbGXUBGnn1kMkgxc8=
 github.com/json-iterator/go v1.1.12 h1:PV8peI4a0ysnczrg+LtxykD8LfKY9ML6u2jnxaEnrnM=
 github.com/json-iterator/go v1.1.12/go.mod h1:e30LSqwooZae/UwlEbR2852Gd8hjQvJoHmT4TnhNGBo=
 github.com/klauspost/compress v1.19.0 h1:sXLILfc9jV2QYWkzFOPWStmcUVH2RHEB1JCdY2oVvCQ=
@@ -225,9 +220,6 @@ github.com/shoenig/go-m1cpu v0.1.6 h1:nxdKQNcEB6vzgA2E2bvzKIYRuNj7XNJ4S/aRSwKzFt
 github.com/shoenig/go-m1cpu v0.1.6/go.mod h1:1JJMcUBvfNwpq05QDQVAnx3gUHr9IYF7GNg9SUEw2VQ=
 github.com/shoenig/test v0.6.4 h1:kVTaSd7WLz5WZ2IaoM0RSzRsUD+m8wRR+5qvntpn4LU=
 github.com/shoenig/test v0.6.4/go.mod h1:byHiCGXqrVaflBLAMq/srcZIHynQPQgeyvkvXnjqq0k=
-github.com/sirupsen/logrus v1.7.0/go.mod h1:yWOB1SBYBC5VeMP7gHvWumXLIWorT60ONWic61uBYv0=
-github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=
-github.com/sirupsen/logrus v1.9.3/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
 github.com/songgao/water v0.0.0-20200317203138-2b4b6d7c09d8 h1:TG/diQgUe0pntT/2D9tmUCz4VNwm9MfrtPr0SU2qSX8=
 github.com/songgao/water v0.0.0-20200317203138-2b4b6d7c09d8/go.mod h1:P5HUIBuIWKbyjl083/loAegFkfbFNx5i2qEP4CNbm7E=
 github.com/sourcegraph/conc v0.3.0 h1:OQTbbt6P72L20UqAkXXuLOj79LfEanQ+YQFNpLA9ySo=
@@ -245,11 +237,8 @@ github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSS
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
 github.com/stretchr/objx v0.5.2 h1:xuMeJ0Sdp5ZMRXx/aWO6RZxdr3beISkG5/G/aIRr3pY=
 github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
-github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
-github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
@@ -286,8 +275,6 @@ github.com/vishvananda/netlink v1.1.1-0.20211118161826-650dca95af54/go.mod h1:tw
 github.com/vishvananda/netns v0.0.0-20200728191858-db3c7e526aae/go.mod h1:DD4vA1DwXk04H54A1oHXtwZmA0grkVMdPxx/VGLCah0=
 github.com/vishvananda/netns v0.0.4 h1:Oeaw1EM2JMxD51g9uhtC0D7erkIjgmj8+JZc26m1YX8=
 github.com/vishvananda/netns v0.0.4/go.mod h1:SpkAiCQRtJ6TvvxPnOSyH3BMl6unz3xZlaprSwhNNJM=
-github.com/vulcand/predicate v1.2.0 h1:uFsW1gcnnR7R+QTID+FVcs0sSYlIGntoGOTb3rQJt50=
-github.com/vulcand/predicate v1.2.0/go.mod h1:VipoNYXny6c8N381zGUWkjuuNHiRbeAZhE7Qm9c+2GA=
 github.com/xjasonlyu/tun2socks/v2 v2.6.0 h1:gI9saJT3XgH4e6v9jBuHRLwK7l3aN9YFWec/SsDTDx4=
 github.com/xjasonlyu/tun2socks/v2 v2.6.0/go.mod h1:35AwqxIxnMkfBfT0UJ1Lku7PZm2ZiZJ8sxHyp0gt1yw=
 github.com/xtaci/kcp-go/v5 v5.6.5 h1:oxGZNobj3OddrLzwdJYnR/waNgwrL98u02u0DWNHE3k=
@@ -334,7 +321,6 @@ golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACk
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20201012173705-84dcc777aaee/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
-golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20210220033148-5ea612d1eb83/go.mod h1:jdWPYTVW3xRLrWPugEBEK3UY2ZEsg3UU495nc5E+M+I=
 golang.org/x/crypto v0.54.0 h1:YLIA59K4fiNzHzjnZt2tUJQjQtUWfWbeHBqKtk3eScw=
 golang.org/x/crypto v0.54.0/go.mod h1:KWL8ny2AZdGR2cWmzeHrp2azQPGogOv+HeQaVEXC2dk=
@@ -355,7 +341,6 @@ golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20201010224723-4f7140c49acb/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
-golang.org/x/net v0.0.0-20201031054903-ff519b6c9102/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
 golang.org/x/net v0.57.0 h1:K5+3DljvIuDG9/Jv9rvyMywYNFCQ9RSUY6OOTTkT+tE=
 golang.org/x/net v0.57.0/go.mod h1:KpXc8iv+r3XplLAG/f7Jsf9RPszJzdR0f58q9vGOuEU=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
@@ -373,7 +358,6 @@ golang.org/x/sys v0.0.0-20200217220822-9197077df867/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200728102440-3e129f6d46b1/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201204225414-ed752295db88/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
@@ -413,7 +397,6 @@ google.golang.org/genproto/googleapis/rpc v0.0.0-20260723215102-3fe39f3c1018/go.
 google.golang.org/grpc v1.19.0/go.mod h1:mqu4LbDTu4XGKhr4mRzUsmM4RtVoemTSY81AxZiDr8c=
 google.golang.org/grpc v1.23.0/go.mod h1:Y5yQAOtifL1yxbo5wqy6BxZv8vAUGQwXBOALyacEbxg=
 google.golang.org/grpc v1.25.1/go.mod h1:c3i+UQWmh7LiEpx4sFZnkU36qjEYZ0imhYfXVyQciAY=
-google.golang.org/grpc v1.27.1/go.mod h1:qbnxyOmOxrQa7FizSgH+ReBfzJrCY1pSN7KXBS8abTk=
 google.golang.org/grpc v1.31.0/go.mod h1:N36X2cJ7JwdamYAgDz+s+rVMFjt3numwzf/HckM8pak=
 google.golang.org/grpc v1.82.1 h1:NnAxzGRA0677vCa4BUkOAnO5+FfQqVl9iUXeD0IqcGE=
 google.golang.org/grpc v1.82.1/go.mod h1:yzTZ1TB1Z3SG+LIYaI+WiE8D5+PZ3ArnrSp8zF3+/ZA=

routing/rules/parser.go

@@ -2,9 +2,12 @@ package rules
 
 import (
 	"fmt"
+	"go/ast"
+	goparser "go/parser"
+	"go/token"
+	"strconv"
 	"strings"
 
-	"github.com/vulcand/predicate"
 	"golang.org/x/text/cases"
 	"golang.org/x/text/language"
 )
@@ -14,8 +17,10 @@ const (
 	or  = "or"
 )
 
-// Parser is an alias for the predicate parser used to parse routing rules.
+// Parser parses a routing rule expression into a TreeBuilder.
-type Parser = predicate.Parser
+type Parser interface {
+	Parse(string) (interface{}, error)
+}
 
 // TreeBuilder defines the type for a Tree builder.
 type TreeBuilder func() *Tree
@@ -32,78 +37,139 @@ type Tree struct {
 }
 
 // NewParser constructs a parser for the given matchers.
-func NewParser(matchers []string) (predicate.Parser, error) {
+//
-	parserFuncs := make(map[string]interface{})
+// Rules are parsed as Go expressions via go/parser, so each matcher is
+// registered under every case variant (exact, lower, upper, title) to make
+// matching case-insensitive. The canonical matcher name (as given) is what
+// ends up in the resulting Tree.
+func NewParser(matchers []string) (Parser, error) {
+	names := make(map[string]string, 4*len(matchers))
+	for _, name := range matchers {
+		names[name] = name
+		names[strings.ToLower(name)] = name
+		names[strings.ToUpper(name)] = name
+		names[cases.Title(language.Und).String(strings.ToLower(name))] = name
+	}
+	return &parser{names: names}, nil
+}
 
-	for _, matcherName := range matchers {
+// parser turns a rule such as `Host("example.com") && !Path("/api")` into a
-		fn := func(value ...string) TreeBuilder {
+// Tree. It reimplements the subset of the previous dependency
-			return func() *Tree {
+// (vulcand/predicate) needed here, so that x no longer pulls in the
-				return &Tree{
+// predicate -> trace -> logrus dependency chain.
-					Matcher: matcherName,
+type parser struct {
-					Value:   value,
+	names map[string]string
-				}
+}
+
+func (p *parser) Parse(rule string) (interface{}, error) {
+	expr, err := goparser.ParseExpr(rule)
+	if err != nil {
+		return nil, err
+	}
+
+	tree, err := p.build(expr)
+	if err != nil {
+		return nil, err
+	}
+
+	return TreeBuilder(func() *Tree { return tree }), nil
+}
+
+// build converts an expression into its Tree.
+func (p *parser) build(expr ast.Expr) (*Tree, error) {
+	switch n := expr.(type) {
+	case *ast.BinaryExpr:
+		left, err := p.build(n.X)
+		if err != nil {
+			return nil, err
+		}
+		right, err := p.build(n.Y)
+		if err != nil {
+			return nil, err
+		}
+		return combine(n.Op, left, right)
+
+	case *ast.ParenExpr:
+		return p.build(n.X)
+
+	case *ast.UnaryExpr:
+		if n.Op != token.NOT {
+			return nil, fmt.Errorf("unsupported operator %v", n.Op)
+		}
+		child, err := p.build(n.X)
+		if err != nil {
+			return nil, err
+		}
+		return invert(child), nil
+
+	case *ast.CallExpr:
+		ident, ok := n.Fun.(*ast.Ident)
+		if !ok {
+			return nil, fmt.Errorf("expected matcher identifier, got %T", n.Fun)
+		}
+		name, ok := p.names[ident.Name]
+		if !ok {
+			return nil, fmt.Errorf("unsupported matcher: %s", ident.Name)
+		}
+
+		values := make([]string, 0, len(n.Args))
+		for _, arg := range n.Args {
+			lit, ok := arg.(*ast.BasicLit)
+			if !ok || lit.Kind != token.STRING {
+				return nil, fmt.Errorf("unsupported argument %v for matcher %s", arg, name)
 			}
+			value, err := strconv.Unquote(lit.Value)
+			if err != nil {
+				return nil, err
+			}
+			values = append(values, value)
 		}
-		parserFuncs[matcherName] = fn
-		parserFuncs[strings.ToLower(matcherName)] = fn
-		parserFuncs[strings.ToUpper(matcherName)] = fn
-		parserFuncs[cases.Title(language.Und).String(strings.ToLower(matcherName))] = fn
-	}
 
-	return predicate.NewParser(predicate.Def{
-		Operators: predicate.Operators{
-			AND: andFunc,
-			OR:  orFunc,
-			NOT: notFunc,
-		},
-		Functions: parserFuncs,
-	})
-}
-
-func andFunc(left, right TreeBuilder) TreeBuilder {
-	return func() *Tree {
 		return &Tree{
-			Matcher:   and,
+			Matcher: name,
-			RuleLeft:  left(),
+			Value:   values,
-			RuleRight: right(),
+		}, nil
-		}
-	}
-}
 
-func orFunc(left, right TreeBuilder) TreeBuilder {
-	return func() *Tree {
-		return &Tree{
-			Matcher:   or,
-			RuleLeft:  left(),
-			RuleRight: right(),
-		}
-	}
-}
-
-func invert(t *Tree) *Tree {
-	switch t.Matcher {
-	case or:
-		t.Matcher = and
-		t.RuleLeft = invert(t.RuleLeft)
-		t.RuleRight = invert(t.RuleRight)
-	case and:
-		t.Matcher = or
-		t.RuleLeft = invert(t.RuleLeft)
-		t.RuleRight = invert(t.RuleRight)
 	default:
-		t.Not = !t.Not
+		return nil, fmt.Errorf("unsupported expression %T", expr)
-	}
-
-	return t
-}
-
-func notFunc(elem TreeBuilder) TreeBuilder {
-	return func() *Tree {
-		return invert(elem())
 	}
 }
 
-// ParseMatchers returns the subset of matchers in the Tree matching the given matchers.
+func combine(op token.Token, left, right *Tree) (*Tree, error) {
+	switch op {
+	case token.LAND:
+		return &Tree{Matcher: and, RuleLeft: left, RuleRight: right}, nil
+	case token.LOR:
+		return &Tree{Matcher: or, RuleLeft: left, RuleRight: right}, nil
+	default:
+		return nil, fmt.Errorf("unsupported operator %v", op)
+	}
+}
+
+// invert returns a new Tree applying De Morgan's law: each internal node's
+// and/or is swapped and every leaf's Not flag is toggled. It never mutates
+// its input.
+func invert(t *Tree) *Tree {
+	n := *t
+	switch n.Matcher {
+	case and:
+		n.Matcher = or
+	case or:
+		n.Matcher = and
+	default:
+		n.Not = !n.Not
+	}
+	if n.RuleLeft != nil {
+		n.RuleLeft = invert(n.RuleLeft)
+	}
+	if n.RuleRight != nil {
+		n.RuleRight = invert(n.RuleRight)
+	}
+	return &n
+}
+
+// ParseMatchers returns the subset of values in the Tree matching the given
+// matchers.
 func (tree *Tree) ParseMatchers(matchers []string) []string {
 	switch tree.Matcher {
 	case and, or:
@@ -114,7 +180,6 @@ func (tree *Tree) ParseMatchers(matchers []string) []string {
 				return lower(tree.Value)
 			}
 		}
-
 		return nil
 	}
 }
@@ -124,13 +189,11 @@ func CheckRule(rule *Tree) error {
 	if len(rule.Value) == 0 {
 		return fmt.Errorf("no args for matcher %s", rule.Matcher)
 	}
-
 	for _, v := range rule.Value {
 		if len(v) == 0 {
 			return fmt.Errorf("empty args for matcher %s, %v", rule.Matcher, rule.Value)
 		}
 	}
-
 	return nil
 }
 
@@ -139,6 +202,5 @@ func lower(slice []string) []string {
 	for _, value := range slice {
 		lowerStrings = append(lowerStrings, strings.ToLower(value))
 	}
-
 	return lowerStrings
 }