Bind param_FILENAME whenever possible

src/main/java/io/jenkins/plugins/file_parameters/AbstractFileParameterDefinition.java

@@ -88,6 +88,7 @@ protected AbstractFileParameterDefinition(String name) {
             }
             src.delete();
             p.setDescription(getDescription());
+            p.filename = src.getName();
             return p;
         } catch (ServletException | IOException x) {
             throw new RuntimeException(x);

src/main/java/io/jenkins/plugins/file_parameters/AbstractFileParameterValue.java

@@ -45,7 +45,9 @@
 /**
  * Implement either {@link #open} and/or {@link #createTempFile}.
  */
-abstract class AbstractFileParameterValue extends ParameterValue {
+public abstract class AbstractFileParameterValue extends ParameterValue {
+
+    @CheckForNull public String filename;
 
     protected AbstractFileParameterValue(String name) {
         super(name);
@@ -88,5 +90,12 @@ public void doDownload(@AncestorInPath Run<?,?> build, StaplerResponse rsp) thro
     }
 
     // TODO equals/hashCode
+
+    @Override public void buildEnvironment(Run<?, ?> build, EnvVars env) {
+        super.buildEnvironment(build, env);
+        if (filename != null) {
+            env.put(name + "_FILENAME", filename);
+        }
+    }
 
 }

src/main/java/io/jenkins/plugins/file_parameters/Base64FileParameterValue.java

@@ -47,6 +47,7 @@ public final class Base64FileParameterValue extends AbstractFileParameterValue {
 
     @DataBoundSetter public void setFile(FileItem file) throws IOException {
         base64 = Base64.getEncoder().encodeToString(IOUtils.toByteArray(file.getInputStream()));
+        filename = file.getName();
         file.delete();
     }
 
@@ -60,6 +61,7 @@ public final class Base64FileParameterValue extends AbstractFileParameterValue {
     }
 
     @Override public void buildEnvironment(Run<?, ?> build, EnvVars env) {
+        super.buildEnvironment(build, env);
         env.put(name, base64);
     }
 

src/main/java/io/jenkins/plugins/file_parameters/StashedFileParameterValue.java

@@ -50,6 +50,7 @@ public final class StashedFileParameterValue extends AbstractFileParameterValue
 
     @DataBoundConstructor public StashedFileParameterValue(String name, FileItem file) throws IOException {
         this(name, file.getInputStream());
+        filename = file.getName();
         file.delete();
     }
 
@@ -61,6 +62,7 @@ public final class StashedFileParameterValue extends AbstractFileParameterValue
     }
 
     @Override public void buildEnvironment(Run<?, ?> build, EnvVars env) {
+        super.buildEnvironment(build, env);
         if (tmp != null) {
             TaskListener listener = TaskListener.NULL; // TODO no option to print to build log
             try {

src/main/resources/io/jenkins/plugins/file_parameters/AbstractFileParameterDefinition/config.jelly

@@ -25,7 +25,7 @@ THE SOFTWARE.
 
 <?jelly escape-by-default='true'?>
 <j:jelly xmlns:j="jelly:core" xmlns:f="/lib/form">
-    <f:entry field="name" title="${%Name}" help="/help/parameter/name.html">
+    <f:entry field="name" title="${%Name}">
         <f:textbox/>
     </f:entry>
     <f:entry field="description" title="${%Description}" help="/help/parameter/description.html">

src/main/resources/io/jenkins/plugins/file_parameters/AbstractFileParameterDefinition/help-name.html

@@ -0,0 +1,8 @@
+<p>
+    The name of the parameter.
+    Depending on the type of parameter, this may or may not be bound as an environment variable during the build.
+</p>
+<p>
+    If a local filename was given, an environment variable <code><i>paramname</i>_FILENAME</code> will also be set.
+    If the build is triggered via the CLI, the variable will not be set.
+</p>

src/main/resources/io/jenkins/plugins/file_parameters/AbstractFileParameterValue/value.jelly

@@ -30,6 +30,6 @@ THE SOFTWARE.
         <j:invokeStatic var="encodedName" className="hudson.Util" method="rawEncode">
             <j:arg value="${it.name}"/>
         </j:invokeStatic>
-        <a href="parameter/${encodedName}/download">${%download}</a>
+        <a href="parameter/${encodedName}/download">${%download} <j:if test="${it.filename != null}"><code>${it.filename}</code></j:if></a>
     </f:entry>
 </j:jelly>

src/test/java/io/jenkins/plugins/file_parameters/AbstractFileParameterDefinitionTest.java

@@ -65,34 +65,34 @@ public class AbstractFileParameterDefinitionTest {
     @Test public void cli() throws Exception {
         WorkflowJob p = r.createProject(WorkflowJob.class, "myjob");
         p.addProperty(new ParametersDefinitionProperty(new Base64FileParameterDefinition("FILE")));
-        p.setDefinition(new CpsFlowDefinition("echo(/received: $FILE/)", true));
+        p.setDefinition(new CpsFlowDefinition("echo(/received $env.FILE_FILENAME: $FILE/)", true));
         assertThat(new CLICommandInvoker(r, "build").
                 withStdin(new ByteArrayInputStream("uploaded content here".getBytes())).
                 invokeWithArgs("-f", "-p", "FILE=", "myjob"),
                 CLICommandInvoker.Matcher.succeeded());
         WorkflowRun b = p.getBuildByNumber(1);
         assertNotNull(b);
-        r.assertLogContains("received: dXBsb2FkZWQgY29udGVudCBoZXJl", b);
+        r.assertLogContains("received null: dXBsb2FkZWQgY29udGVudCBoZXJl", b);
     }
 
     @Test public void rest() throws Exception {
         r.jenkins.setSecurityRealm(r.createDummySecurityRealm());
         r.jenkins.setAuthorizationStrategy(new MockAuthorizationStrategy().grant(Jenkins.ADMINISTER).everywhere().to("admin"));
         WorkflowJob p = r.createProject(WorkflowJob.class, "myjob");
         p.addProperty(new ParametersDefinitionProperty(new Base64FileParameterDefinition("FILE")));
-        p.setDefinition(new CpsFlowDefinition("echo(/received: $FILE/)", true));
+        p.setDefinition(new CpsFlowDefinition("echo(/received $FILE_FILENAME: $FILE/)", true));
         // Like: curl -u $auth -F FILE=@/tmp/f $jenkins/job/myjob/buildWithParameters
         WebRequest req = new WebRequest(new URL(r.getURL() + "job/myjob/buildWithParameters"), HttpMethod.POST);
         File f = tmp.newFile();
         FileUtils.write(f, "uploaded content here", "UTF-8");
         req.setEncodingType(FormEncodingType.MULTIPART);
-        req.setRequestParameters(Collections.<NameValuePair>singletonList(new KeyDataPair("FILE", f, "FILE", "text/plain", "UTF-8")));
+        req.setRequestParameters(Collections.<NameValuePair>singletonList(new KeyDataPair("FILE", f, "myfile.txt", "text/plain", "UTF-8")));
         User.getById("admin", true); // TODO workaround for https://github.com/jenkinsci/jenkins-test-harness/pull/273
         r.createWebClient().withBasicApiToken("admin").getPage(req);
         r.waitUntilNoActivity();
         WorkflowRun b = p.getBuildByNumber(1);
         assertNotNull(b);
-        r.assertLogContains("received: dXBsb2FkZWQgY29udGVudCBoZXJl", b);
+        r.assertLogContains("received myfile.txt: dXBsb2FkZWQgY29udGVudCBoZXJl", b);
     }
 
 }