Structured pattern errors with position tracking

.github/workflows/tests.yaml

@@ -3,13 +3,16 @@ on:
   push:
   workflow_dispatch:
 
+permissions:
+  contents: read
+
 jobs:
   test:
     name: Test Fox
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: [ '>=1.24' ]
+        go: [ '>=1.26' ]
     steps:
       - name: Set up Go
         uses: actions/setup-go@v6
@@ -19,6 +22,8 @@ jobs:
 
       - name: Check out code
         uses: actions/checkout@v6
+        with:
+          persist-credentials: false
 
       - name: Run tests
         run: go test -v -coverprofile=coverage.txt -covermode=atomic ./...
@@ -37,7 +42,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: [ '>=1.24' ]
+        go: [ '>=1.26' ]
     steps:
       - name: Set up Go
         uses: actions/setup-go@v6
@@ -47,6 +52,8 @@ jobs:
 
       - name: Check out code
         uses: actions/checkout@v6
+        with:
+          persist-credentials: false
 
       - name: Run linter
         uses: golangci/golangci-lint-action@v9

error.go

@@ -19,10 +19,7 @@ var (
 	ErrNoClientIPResolver      = errors.New("no client ip resolver")
 	ErrReadOnlyTxn             = errors.New("write on read-only transaction")
 	ErrSettledTxn              = errors.New("transaction settled")
-	ErrParamKeyTooLarge        = errors.New("parameter key too large")
-	ErrTooManyParams           = errors.New("too many params")
 	ErrTooManyMatchers         = errors.New("too many matchers")
-	ErrRegexpNotAllowed        = errors.New("regexp not allowed")
 	ErrInvalidConfig           = errors.New("invalid config")
 	ErrInvalidMatcher          = errors.New("invalid matcher")
 )
@@ -44,7 +41,7 @@ func (e *RouteConflictError) Error() string {
 	routef(sb, e.New, 4, true)
 
 	if e.isShadowed {
-		if e.New.catchEmpty {
+		if e.New.pattern.optionalCatchAll {
 			sb.WriteString("\nis shadowed by")
 		} else {
 			sb.WriteString("\nwould shadow")
@@ -96,3 +93,58 @@ func newRouteNotFoundError(route *Route) error {
 	sb.WriteString("\nis not registered")
 	return fmt.Errorf("%w: %s", ErrRouteNotFound, sb.String())
 }
+
+type PatternError struct {
+	err     error  // wrapped error
+	Pattern string // provided pattern
+	Type    string // hostname | path
+	Reason  string // syntax | parameter | regexp | constraint
+	Hint    string // hint
+	Start   int    // start offset of the offending segment
+	End     int    // end offset of the offending segment
+}
+
+// Unwrap returns the underlying error, if any.
+func (e *PatternError) Unwrap() error {
+	return e.err
+}
+
+// Error returns a human-readable error message with a visual pointer to the offending segment.
+func (e *PatternError) Error() string {
+	var sb strings.Builder
+	sb.WriteString("pattern: ")
+	if e.Type != "" {
+		sb.WriteString(e.Type)
+		sb.WriteString(": ")
+	}
+	sb.WriteString(e.Reason)
+	sb.WriteString(": ")
+	sb.WriteString(e.Hint)
+	if e.Pattern != "" {
+		sb.WriteByte('\n')
+		sb.WriteString("      ")
+		sb.WriteString(e.Pattern)
+		sb.WriteByte('\n')
+		sb.WriteString("      ")
+		for i := 0; i < e.Start; i++ {
+			sb.WriteByte(' ')
+		}
+		n := e.End - e.Start
+		if n <= 0 {
+			n = 1
+		}
+		for i := 0; i < n; i++ {
+			sb.WriteByte('^')
+		}
+	}
+	return sb.String()
+}
+
+func newPatternError(reason string, start, end int, msg string) *PatternError {
+	return &PatternError{
+		Reason: reason,
+		Start:  start,
+		End:    end,
+		Hint:   msg,
+	}
+}