Refine RequestMappingInfo path initialization

Refining the change from 4370030 so that
we consistently pick a PathPatternParser (a) if it is provided, and (b)
if both PathPatternParser and PathMatcher are not provided. Also applying
the same in the mutate builder.

See gh-31662

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/RequestMappingInfo.java

@@ -708,20 +708,21 @@ public RequestMappingInfo build() {
 			PathPatternsRequestCondition pathPatternsCondition = null;
 			PatternsRequestCondition patternsCondition = null;
 
-			if (this.options.getPathMatcher() != null) {
+			PathPatternParser parser = this.options.getPatternParserToUse();
+
+			if (parser != null) {
+				pathPatternsCondition = (ObjectUtils.isEmpty(this.paths) ?
+						EMPTY_PATH_PATTERNS :
+						new PathPatternsRequestCondition(parser, this.paths));
+			}
+			else {
 				patternsCondition = (ObjectUtils.isEmpty(this.paths) ?
 						EMPTY_PATTERNS :
 						new PatternsRequestCondition(
-								this.paths, null, this.options.getPathMatcher(),
+								this.paths, null, this.options.pathMatcher,
 								this.options.useSuffixPatternMatch(), this.options.useTrailingSlashMatch(),
 								this.options.getFileExtensions()));
 			}
-			else {
-				PathPatternParser parser = (this.options.getPatternParser() != null ?
-						this.options.getPatternParser() : new PathPatternParser());
-				pathPatternsCondition = (ObjectUtils.isEmpty(this.paths) ?
-						EMPTY_PATH_PATTERNS : new PathPatternsRequestCondition(parser, this.paths));
-			}
 
 			ContentNegotiationManager manager = this.options.getContentNegotiationManager();
 
@@ -784,9 +785,11 @@ public MutateBuilder(RequestMappingInfo other) {
 		@Override
 		@SuppressWarnings("deprecation")
 		public Builder paths(String... paths) {
-			if (this.options.patternParser != null) {
+			PathPatternParser parser = this.options.getPatternParserToUse();
+
+			if (parser != null) {
 				this.pathPatternsCondition = (ObjectUtils.isEmpty(paths) ?
-						EMPTY_PATH_PATTERNS : new PathPatternsRequestCondition(this.options.patternParser, paths));
+						EMPTY_PATH_PATTERNS : new PathPatternsRequestCondition(parser, paths));
 			}
 			else {
 				this.patternsCondition = (ObjectUtils.isEmpty(paths) ?
@@ -873,6 +876,9 @@ public RequestMappingInfo build() {
 	 */
 	public static class BuilderConfiguration {
 
+		private static PathPatternParser defaultPatternParser = new PathPatternParser();
+
+
 		@Nullable
 		private PathPatternParser patternParser;
 
@@ -954,6 +960,20 @@ public PathMatcher getPathMatcher() {
 			return this.pathMatcher;
 		}
 
+		/**
+		 * Return the {@code PathPatternParser} to use, the one set explicitly
+		 * or falling back on a default instance if both {@code PathPatternParser}
+		 * and {@code PathMatcher} are not set.
+		 * @since 6.1.2
+		 */
+		@Nullable
+		public PathPatternParser getPatternParserToUse() {
+			if (this.patternParser == null && this.pathMatcher == null) {
+				return defaultPatternParser;
+			}
+			return this.patternParser;
+		}
+
 		/**
 		 * Set whether to apply trailing slash matching in PatternsRequestCondition.
 		 * <p>The default was changed in 6.0 from {@code true} to {@code false} in