Another fix to how the UNC paths are handled (a workaround similar to the one applied in SBT: sbt/sbt#564)

Build Monitor should load its LESS CSS assets correctly from a mapped network folder defined as a UNC path on Windows as long as:
- Build Monitor runs on Jenkins 1.598 or later (due to a bug in Jenkins prior to that version: http://jenkins-ci.org/changelog#v1.598)
- Jenkins runs on Java 7 u60 or later (due to a bug in Java prior to that version: http://bugs.java.com/view_bug.do?bug_id=8014394)

Fixes jenkinsci#183

Author: jan-molak

src/main/java/com/smartcodeltd/jenkinsci/plugin/assetbundler/Dispatcher.java

@@ -5,7 +5,7 @@
 import hudson.Plugin;
 import hudson.util.PluginServletFilter;
 
-import java.net.URI;
+import java.io.File;
 import java.net.URISyntaxException;
 import java.net.URL;
 
@@ -31,7 +31,7 @@ private URL baseResourceURL() {
         return getWrapper().parent.getPlugin("build-monitor-plugin").baseResourceURL;
     }
 
-    private URI pathTo(String asset) throws URISyntaxException {
-        return new PathToAsset(baseResourceURL(), asset).toURI();
+    private File pathTo(String asset) throws URISyntaxException {
+        return new PathToAsset(baseResourceURL(), asset).toFile();
     }
 }

src/main/java/com/smartcodeltd/jenkinsci/plugin/assetbundler/PathToAsset.java

@@ -7,23 +7,47 @@
 import static java.lang.String.format;
 
 public class PathToAsset {
-    private final URL root;
-    private final String asset;
+    private static final String FILE_PROTOCOL = "file";
+    private final URI path;
 
     public PathToAsset(URL root, String asset) {
-        this.root = root;
-        this.asset = asset;
+        this.path = validated(uriFrom(root, asset));
     }
 
-    public URI toURI() {
+    public File toFile() {
+        /*
+         * The below workaround is required as the `uri` representing a UNC path on Windows
+         * has an `authority` component defined (//foo/bar/some/file.ext),
+         * however the File class constructor requires URIs with no defined authority
+         *
+         * https://github.com/jan-molak/jenkins-build-monitor-plugin/issues/183#issuecomment-157712010
+         *
+         * http://blogs.msdn.com/b/ie/archive/2006/12/06/file-uris-in-windows.aspx
+         * http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5086147
+         *
+         * fix as per: https://github.com/sbt/sbt/issues/564
+         */
+
+        return (null == path.getAuthority())
+                ? new File(path)
+                : new File(path.getSchemeSpecificPart());
+    }
+
+    // --
+
+    private URI uriFrom(URL root, String asset) {
         try {
             return new URL(root, asset).toURI();
         } catch (Exception e) {
-            throw new RuntimeException(format("Sorry, I couldn't construct a path to asset '%s' using root: '%s", asset, root));
+            throw new IllegalArgumentException(format("Sorry, I couldn't construct a path to asset '%s' using root: '%s", asset, root));
         }
     }
 
-    public File toFile() {
-        return new File(toURI());
+    private URI validated(URI fileUri) {
+        if (! FILE_PROTOCOL.equals(fileUri.getScheme())) {
+            throw new IllegalArgumentException(format("Sorry, can't load the asset from '%s' using the '%s' protocol", fileUri, FILE_PROTOCOL));
+        }
+
+        return fileUri;
     }
 }

src/main/java/com/smartcodeltd/jenkinsci/plugin/assetbundler/filters/LessCSS.java

@@ -10,24 +10,23 @@
 import javax.servlet.http.HttpServletResponse;
 import java.io.File;
 import java.io.IOException;
-import java.net.URI;
 import java.net.URISyntaxException;
 
 public class LessCSS implements Filter {
-    private final File   less;
+    private final File lessFile;
     private final String pathToCSS;
 
     private String compiledCSS;
 
-    public LessCSS(String pathToCSS, URI pathToLess) throws URISyntaxException {
+    public LessCSS(String pathToCSS, File pathToLess) throws URISyntaxException {
         this.pathToCSS  = pathToCSS;
-        this.less       = new File(pathToLess);
+        this.lessFile   = pathToLess;
     }
 
     @Override
     public void init(FilterConfig filterConfig) throws ServletException {
         try {
-            compiledCSS = cssFrom(less);
+            compiledCSS = cssFrom(lessFile);
         } catch (Less4jException e) {
             throw new ServletException("Couldn't compile the CSS from LESS sources", e);
         }

src/test/java/com/smartcodeltd/jenkinsci/plugin/assetbundler/PathToAssetTest.java

@@ -1,37 +1,53 @@
 package com.smartcodeltd.jenkinsci.plugin.assetbundler;
 
-import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 import java.net.MalformedURLException;
 import java.net.URL;
 
-import static com.smartcodeltd.jenkinsci.plugin.assetbundler.OsSpecific.isNotWindows;
 import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.assertThat;
-import static org.junit.Assume.assumeTrue;
 
 public class PathToAssetTest {
-    @Before
-    public void checkOS() {
-        // todo: Build Monitor should use Java 7 once its core dependency on Jenkins can be upgraded to 1.612
-        assumeTrue(isNotWindows());
-    }
 
     @Test
     public void combines_base_resource_url_given_by_jenkins_and_a_path_to_the_asset() throws Exception {
-        URL base = baseResourceUrlGivenByJenkins("/opt/jenkins/plugins/build-monitor-plugin/");
+        URL base = baseResourceUrlGivenByJenkins("file:///opt/jenkins/plugins/build-monitor-plugin/");
 
         PathToAsset path = new PathToAsset(base, "less/index.less");
 
         assertThat(absolute(path), is("/opt/jenkins/plugins/build-monitor-plugin/less/index.less"));
     }
 
+    @Test
+    public void works_with_unc_paths_on_windows() throws Exception {
+        URL base = baseResourceUrlGivenByJenkins("file://server/jenkins/plugins/build-monitor-plugin/");
+
+        PathToAsset path = new PathToAsset(base, "less/index.less");
+
+        assertThat(absolute(path), is("/server/jenkins/plugins/build-monitor-plugin/less/index.less"));
+    }
+
+    @Rule public ExpectedException thrown = ExpectedException.none();
+
+    @Test
+    public void complains_when_given_a_non_file_base_resource_url() throws Exception {
+        thrown.expect(IllegalArgumentException.class);
+        thrown.expectMessage("Sorry, can't load the asset from 'http://google.com/less/index.less' using the 'file' protocol");
+
+        new PathToAsset(new URL("http://google.com"), "less/index.less");
+    }
+
+    // --
+
     private String absolute(PathToAsset path) {
         return path.toFile().getAbsolutePath();
     }
 
-    private URL baseResourceUrlGivenByJenkins(String path) throws MalformedURLException {
-        return new URL("file://" + path);
+    // a pass-through method, only here for readability purposes
+    private URL baseResourceUrlGivenByJenkins(String url) throws MalformedURLException {
+        return new URL(url);
     }
 }