Fix kebab and snake case formatting of all upper case words

Closes gh-658

Author: wilkinsona

spring-restdocs-core/src/main/java/org/springframework/restdocs/snippet/RestDocumentationContextPlaceholderResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,9 +16,6 @@
 
 package org.springframework.restdocs.snippet;
 
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-
 import org.springframework.restdocs.RestDocumentationContext;
 import org.springframework.util.PropertyPlaceholderHelper.PlaceholderResolver;
 
@@ -51,8 +48,6 @@
  */
 public class RestDocumentationContextPlaceholderResolver implements PlaceholderResolver {
 
-	private static final Pattern CAMEL_CASE_PATTERN = Pattern.compile("([A-Z])");
-
 	private final RestDocumentationContext context;
 
 	/**
@@ -130,14 +125,18 @@ protected final RestDocumentationContext getContext() {
 	}
 
 	private String camelCaseToSeparator(String string, String separator) {
-		Matcher matcher = CAMEL_CASE_PATTERN.matcher(string);
 		StringBuffer result = new StringBuffer();
-		while (matcher.find()) {
-			String replacement = (matcher.start() > 0) ? separator + matcher.group(1).toLowerCase()
-					: matcher.group(1).toLowerCase();
-			matcher.appendReplacement(result, replacement);
+		char[] chars = string.toCharArray();
+		for (int i = 0; i < chars.length; i++) {
+			char current = chars[i];
+			if (Character.isUpperCase(current) && i > 0) {
+				if (Character.isLowerCase(chars[i - 1])
+						|| (i < chars.length - 1 && Character.isLowerCase(chars[i + 1]))) {
+					result.append(separator);
+				}
+			}
+			result.append(Character.toLowerCase(chars[i]));
 		}
-		matcher.appendTail(result);
 		return result.toString();
 	}
 

spring-restdocs-core/src/test/java/org/springframework/restdocs/snippet/RestDocumentationContextPlaceholderResolverTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,12 +38,48 @@ public void kebabCaseMethodName() throws Exception {
 				.isEqualTo("dash-separated-method-name");
 	}
 
+	@Test
+	public void kebabCaseMethodNameWithUpperCaseOpeningSection() throws Exception {
+		assertThat(createResolver("URIDashSeparatedMethodName").resolvePlaceholder("method-name"))
+				.isEqualTo("uri-dash-separated-method-name");
+	}
+
+	@Test
+	public void kebabCaseMethodNameWithUpperCaseMidSection() throws Exception {
+		assertThat(createResolver("dashSeparatedMethodNameWithURIInIt").resolvePlaceholder("method-name"))
+				.isEqualTo("dash-separated-method-name-with-uri-in-it");
+	}
+
+	@Test
+	public void kebabCaseMethodNameWithUpperCaseEndSection() throws Exception {
+		assertThat(createResolver("dashSeparatedMethodNameWithURI").resolvePlaceholder("method-name"))
+				.isEqualTo("dash-separated-method-name-with-uri");
+	}
+
 	@Test
 	public void snakeCaseMethodName() throws Exception {
 		assertThat(createResolver("underscoreSeparatedMethodName").resolvePlaceholder("method_name"))
 				.isEqualTo("underscore_separated_method_name");
 	}
 
+	@Test
+	public void snakeCaseMethodNameWithUpperCaseOpeningSection() throws Exception {
+		assertThat(createResolver("URIUnderscoreSeparatedMethodName").resolvePlaceholder("method_name"))
+				.isEqualTo("uri_underscore_separated_method_name");
+	}
+
+	@Test
+	public void snakeCaseMethodNameWithUpperCaseMidSection() throws Exception {
+		assertThat(createResolver("underscoreSeparatedMethodNameWithURIInIt").resolvePlaceholder("method_name"))
+				.isEqualTo("underscore_separated_method_name_with_uri_in_it");
+	}
+
+	@Test
+	public void snakeCaseMethodNameWithUpperCaseEndSection() throws Exception {
+		assertThat(createResolver("underscoreSeparatedMethodNameWithURI").resolvePlaceholder("method_name"))
+				.isEqualTo("underscore_separated_method_name_with_uri");
+	}
+
 	@Test
 	public void camelCaseMethodName() throws Exception {
 		assertThat(createResolver("camelCaseMethodName").resolvePlaceholder("methodName"))