Fix config file as URL on Windows

Configuration for various formatter steps can be located in separate
files. Such files might live in the local filesystem and be identified
as simple paths. They can also be remote files identified by a URL.
Both types of files are copied to the output directory using Maven's
`ResourceManager` which can handle both local and remote files.

Previously, plugin tried to deduce the output file name based on the
configured string. This was done using `FileUtils#filename()` method
that expects to only work with system file separators. Issue occurred
on Windows when URL was specified. Path separator on Windows is `\`
and in URL it is `/`. Code wasn't able to extract the last path of
the URL that denotes the file name. Instead, it treated the whole URL
as a file name. URLs contain chars invalid for Windows paths and an
exception was thrown on attempt to create the file.

This commit fixes the problem by making code use predefined name
pattern for all resolved resources. Name of the output file will not
be guessed based on the configured path or URL. It will just be unique
and have 'spotless-resource-' prefix.

Author: lutovich

plugin-maven/src/main/java/com/diffplug/spotless/maven/FileLocator.java

@@ -15,9 +15,10 @@
  */
 package com.diffplug.spotless.maven;
 
-import static com.diffplug.common.base.Strings.*;
+import static com.diffplug.common.base.Strings.isNullOrEmpty;
 
 import java.io.File;
+import java.util.UUID;
 
 import org.codehaus.plexus.resource.ResourceManager;
 import org.codehaus.plexus.resource.loader.FileResourceCreationException;
@@ -26,6 +27,8 @@
 
 public class FileLocator {
 
+	static final String TMP_RESOURCE_FILE_PREFIX = "spotless-resource-";
+
 	private final ResourceManager resourceManager;
 
 	public FileLocator(ResourceManager resourceManager) {
@@ -48,9 +51,7 @@ public File locateFile(String path) {
 	}
 
 	private static String tmpOutputFileName(String path) {
-		String nameWithExtension = FileUtils.filename(path);
 		String extension = FileUtils.extension(path);
-		String name = nameWithExtension.replace('.' + extension, "");
-		return name + '-' + System.currentTimeMillis() + '.' + extension;
+		return TMP_RESOURCE_FILE_PREFIX + UUID.randomUUID() + '.' + extension;
 	}
 }

plugin-maven/src/test/java/com/diffplug/spotless/maven/FileLocatorTest.java

@@ -15,14 +15,13 @@
  */
 package com.diffplug.spotless.maven;
 
+import static com.diffplug.spotless.maven.FileLocator.TMP_RESOURCE_FILE_PREFIX;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.eq;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.when;
+import static org.mockito.Mockito.*;
 
 import java.io.File;
 import java.nio.file.Paths;
@@ -47,17 +46,32 @@ public void locateNull() {
 	}
 
 	@Test
-	public void locateValidFile() throws Exception {
-		String path = Paths.get("tmp", "configs", "my-config.xml").toString();
-		File tmpOutputFile = new File("tmp-my-config.xml");
+	public void locateXmlFile() throws Exception {
+		testFileLocator(Paths.get("tmp", "configs", "my-config.xml").toString(), "xml");
+	}
+
+	@Test
+	public void locatePropertiesFile() throws Exception {
+		testFileLocator(Paths.get("home", "ubuntu", "my-other-config.properties").toString(), "properties");
+	}
+
+	@Test
+	public void locateConfFileWithIncorrectSeparators() throws Exception {
+		String oppositeSeparator = "/".equals(File.separator) ? "\\" : "/";
+		String path = "tmp" + oppositeSeparator + "configs" + oppositeSeparator + "hello.conf";
+
+		testFileLocator(path, "conf");
+	}
+
+	private void testFileLocator(String path, String extension) throws Exception {
+		File tmpOutputFile = new File("tmp-file");
 		when(resourceManager.getResourceAsFile(any(), any())).thenReturn(tmpOutputFile);
 
 		File locatedFile = fileLocator.locateFile(path);
-
 		assertEquals(tmpOutputFile, locatedFile);
 
 		ArgumentCaptor<String> argCaptor = ArgumentCaptor.forClass(String.class);
 		verify(resourceManager).getResourceAsFile(eq(path), argCaptor.capture());
-		assertThat(argCaptor.getValue()).startsWith("my-config").endsWith(".xml");
+		assertThat(argCaptor.getValue()).startsWith(TMP_RESOURCE_FILE_PREFIX).endsWith('.' + extension);
 	}
 }