[examples] Add tasks to run Java examples (#2920)

Example: ./gradlew :wpilibjExamples:runstatespacedifferentialdrivesimulation

wpilibjExamples/build.gradle

@@ -1,3 +1,5 @@
+import edu.wpi.first.toolchain.NativePlatforms
+
 apply plugin: 'java'
 apply plugin: 'jacoco'
 
@@ -83,6 +85,115 @@ ext {
     commandFile = new File("$projectDir/src/main/java/edu/wpi/first/wpilibj/commands/commands.json")
 }
 
+apply plugin: 'cpp'
+apply plugin: 'edu.wpi.first.NativeUtils'
+
+apply from: '../shared/config.gradle'
+
+
+model {
+    components {
+        wpilibjExamplesDev(NativeExecutableSpec) {
+            targetBuildTypes 'debug'
+            sources {
+                cpp {
+                    source {
+                        srcDirs 'src/dev/native/cpp'
+                        include '**/*.cpp'
+                    }
+                    exportedHeaders {
+                        srcDirs 'src/dev/native/include'
+                    }
+                }
+            }
+            binaries.all { binary ->
+                lib project: ':wpilibOldCommands', library: 'wpilibOldCommands', linkage: 'shared'
+                lib project: ':wpilibNewCommands', library: 'wpilibNewCommands', linkage: 'shared'
+                lib project: ':wpilibc', library: 'wpilibc', linkage: 'shared'
+                lib project: ':wpimath', library: 'wpimath', linkage: 'shared'
+                lib project: ':ntcore', library: 'ntcore', linkage: 'shared'
+                lib project: ':cscore', library: 'cscore', linkage: 'shared'
+                lib project: ':ntcore', library: 'ntcoreJNIShared', linkage: 'shared'
+                lib project: ':cscore', library: 'cscoreJNIShared', linkage: 'shared'
+                project(':hal').addHalDependency(binary, 'shared')
+                project(':hal').addHalJniDependency(binary)
+                lib project: ':wpiutil', library: 'wpiutil', linkage: 'shared'
+                lib project: ':cameraserver', library: 'cameraserver', linkage: 'shared'
+                if (binary.targetPlatform.name == nativeUtils.wpi.platforms.roborio) {
+                    nativeUtils.useRequiredLibrary(binary, 'netcomm_shared', 'chipobject_shared', 'visa_shared', 'ni_runtime_shared')
+                } else {
+                    def systemArch = getCurrentArch()
+                    if (binary.targetPlatform.name == systemArch) {
+                        lib project: ":simulation:halsim_gui", library: 'halsim_gui', linkage: 'shared'
+                    }
+                }
+                nativeUtils.useRequiredLibrary(binary, 'opencv_shared')
+            }
+        }
+    }
+    tasks {
+        def c = $.components
+        def found = false
+        c.each {
+            if (it in NativeExecutableSpec && it.name == "wpilibjExamplesDev") {
+                it.binaries.each {
+                    if (!found) {
+                        def arch = it.targetPlatform.name
+                        if (arch == NativePlatforms.desktop) {
+                            found = true
+                            def filePath = it.tasks.install.installDirectory.get().toString() + File.separatorChar + 'lib'
+
+                            def doFirstTask = { task ->
+                                def extensions = ''
+                                it.tasks.install.installDirectory.get().getAsFile().eachFileRecurse {
+                                    def name = it.name
+                                    if (!(name.endsWith('.dll') || name.endsWith('.so') || name.endsWith('.dylib'))) {
+                                        return
+                                    }
+                                    def file = it
+                                    if (name.startsWith("halsim_gui") || name.startsWith("libhalsim_gui".toString())) {
+                                        extensions += file.absolutePath + File.pathSeparator
+                                    }
+                                }
+                                if (extensions != '') {
+                                    task.environment 'HALSIM_EXTENSIONS', extensions
+                                }
+                            }
+
+                            project.tasks.create("runCpp", Exec) { task ->
+                                dependsOn it.tasks.install
+                                commandLine it.tasks.install.runScriptFile.get().asFile.toString()
+                                test.dependsOn it.tasks.install
+                                test.systemProperty 'java.library.path', filePath
+                                test.environment 'LD_LIBRARY_PATH', filePath
+                                test.workingDir filePath
+                            }
+
+                            new groovy.json.JsonSlurper().parseText(exampleFile.text).each { entry ->
+                                project.tasks.create("run${entry.foldername}", JavaExec) { run ->
+                                    main = "edu.wpi.first.wpilibj.examples." + entry.foldername + ".Main"
+                                    classpath = sourceSets.main.runtimeClasspath
+                                    run.dependsOn it.tasks.install
+                                    run.systemProperty 'java.library.path', filePath
+                                    run.environment 'LD_LIBRARY_PATH', filePath
+                                    run.workingDir filePath
+                                    doFirst { doFirstTask(run) }
+
+                                    if (org.gradle.internal.os.OperatingSystem.current().isMacOsX()) {
+                                        run.jvmArgs = ['-XstartOnFirstThread']
+                                    }
+                                }
+                            }
+
+                            found = true
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
 ext {
     isCppCommands = false
 }

wpilibjExamples/src/dev/native/cpp/main.cpp

@@ -0,0 +1,8 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2020 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+int main() {}