openapi3: support \uC4FE codepoint syntax in Schema.Pattern (#873)

openapi3/schema.go

@@ -2011,22 +2011,6 @@ func (schema *Schema) expectedType(settings *schemaValidationSettings, value int
 	}
 }
 
-// NOTE: racey WRT [writes to schema.Pattern] vs [reads schema.Pattern then writes to compiledPatterns]
-func (schema *Schema) compilePattern() (cp *regexp.Regexp, err error) {
-	pattern := schema.Pattern
-	if cp, err = regexp.Compile(pattern); err != nil {
-		err = &SchemaError{
-			Schema:      schema,
-			SchemaField: "pattern",
-			Origin:      err,
-			Reason:      fmt.Sprintf("cannot compile pattern %q: %v", pattern, err),
-		}
-		return
-	}
-	var _ bool = compiledPatterns.CompareAndSwap(pattern, nil, cp)
-	return
-}
-
 // SchemaError is an error that occurs during schema validation.
 type SchemaError struct {
 	// Value is the value that failed validation.

openapi3/schema_pattern.go

@@ -0,0 +1,29 @@
+package openapi3
+
+import (
+	"fmt"
+	"regexp"
+)
+
+var patRewriteCodepoints = regexp.MustCompile(`[\][u]([0-9A-F]{4})`)
+
+// See https://pkg.go.dev/regexp/syntax
+func intoGoRegexp(re string) string {
+	return patRewriteCodepoints.ReplaceAllString(re, `x{$1}`)
+}
+
+// NOTE: racey WRT [writes to schema.Pattern] vs [reads schema.Pattern then writes to compiledPatterns]
+func (schema *Schema) compilePattern() (cp *regexp.Regexp, err error) {
+	pattern := schema.Pattern
+	if cp, err = regexp.Compile(intoGoRegexp(pattern)); err != nil {
+		err = &SchemaError{
+			Schema:      schema,
+			SchemaField: "pattern",
+			Origin:      err,
+			Reason:      fmt.Sprintf("cannot compile pattern %q: %v", pattern, err),
+		}
+		return
+	}
+	var _ bool = compiledPatterns.CompareAndSwap(pattern, nil, cp)
+	return
+}

openapi3/schema_pattern_test.go

@@ -0,0 +1,18 @@
+package openapi3
+
+import (
+	"regexp"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestPattern(t *testing.T) {
+	_, err := regexp.Compile("^[a-zA-Z\\u0080-\\u024F\\s\\/\\-\\)\\(\\`\\.\\\"\\']+$")
+	require.EqualError(t, err, "error parsing regexp: invalid escape sequence: `\\u`")
+
+	_, err = regexp.Compile(`^[a-zA-Z\x{0080}-\x{024F}]+$`)
+	require.NoError(t, err)
+
+	require.Equal(t, `^[a-zA-Z\x{0080}-\x{024F}]+$`, intoGoRegexp(`^[a-zA-Z\u0080-\u024F]+$`))
+}