Support configuring run environment variables & Fixes #653

src/main/java/net/fabricmc/loom/configuration/ide/RunConfig.java

@@ -30,11 +30,13 @@ import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 import com.google.common.collect.ImmutableMap;
 import com.google.gson.JsonElement;
@@ -68,6 +70,8 @@ public class RunConfig {
 	public List<String> vmArgs = new ArrayList<>();
 	public List<String> programArgs = new ArrayList<>();
 	public SourceSet sourceSet;
+	public Map<String, Object> environmentVariables;
+	public String projectName;
 
 	public Element genRuns(Element doc) {
 		Element root = this.addXml(doc, "component", ImmutableMap.of("name", "ProjectRunConfigurationManager"));
@@ -174,6 +178,9 @@ public class RunConfig {
 		runConfig.programArgs.addAll(settings.getProgramArgs());
 		runConfig.vmArgs.addAll(settings.getVmArgs());
 		runConfig.vmArgs.add("-Dfabric.dli.main=" + getMainClass(environment, extension, defaultMain));
+		runConfig.environmentVariables = new HashMap<>();
+		runConfig.environmentVariables.putAll(settings.getEnvironmentVariables());
+		runConfig.projectName = project.getName();
 
 		return runConfig;
 	}
@@ -202,10 +209,19 @@ public class RunConfig {
 		dummyConfig = dummyConfig.replace("%RUN_DIRECTORY%", runDir);
 		dummyConfig = dummyConfig.replace("%PROGRAM_ARGS%", joinArguments(programArgs).replaceAll("\"", "&quot;"));
 		dummyConfig = dummyConfig.replace("%VM_ARGS%", joinArguments(vmArgs).replaceAll("\"", "&quot;"));
+		dummyConfig = dummyConfig.replace("%IDEA_ENV_VARS%", getEnvVars("<env name=\"%s\" value=\"%s\"/>"));
+		dummyConfig = dummyConfig.replace("%ECLIPSE_ENV_VARS%", getEnvVars("<mapEntry key=\"%s\" value=\"%s\"/>"));
 
 		return dummyConfig;
 	}
 
+	private String getEnvVars(String pattern) {
+		return environmentVariables.entrySet().stream()
+			.map(entry ->
+				pattern.formatted(entry.getKey(), entry.getValue().toString())
+			).collect(Collectors.joining());
+	}
+
 	public static String joinArguments(List<String> args) {
 		final var sb = new StringBuilder();
 		boolean first = true;

src/main/java/net/fabricmc/loom/configuration/ide/RunConfigSettings.java

@@ -28,6 +28,7 @@ import java.io.File;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
@@ -95,6 +96,8 @@ public final class RunConfigSettings implements Named {
 	 */
 	private boolean ideConfigGenerated;
 
+	private final Map<String, Object> environmentVariables = new HashMap<>();
+
 	private final Project project;
 	private final LoomGradleExtension extension;
 
@@ -241,6 +244,14 @@ public final class RunConfigSettings implements Named {
 		this.ideConfigGenerated = ideConfigGenerated;
 	}
 
+	public Map<String, Object> getEnvironmentVariables() {
+		return environmentVariables;
+	}
+
+	public void environmentVariable(String name, Object value) {
+		environmentVariables.put(name, value);
+	}
+
 	/**
 	 * Add the {@code -XstartOnFirstThread} JVM argument when on OSX.
 	 */

src/main/java/net/fabricmc/loom/task/AbstractRunTask.java

@@ -53,6 +53,7 @@ public abstract class AbstractRunTask extends JavaExec {
 	@Override
 	public void exec() {
 		setWorkingDir(new File(getProject().getProjectDir(), config.runDir));
+		environment(config.environmentVariables);
 
 		super.exec();
 	}

src/main/java/net/fabricmc/loom/task/GenVsCodeProjectTask.java

@@ -29,7 +29,9 @@ import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 import org.apache.commons.io.FileUtils;
 import org.gradle.api.Project;
@@ -99,6 +101,8 @@ public class GenVsCodeProjectTask extends AbstractLoomTask {
 		public String mainClass;
 		public String vmArgs;
 		public String args;
+		public Map<String, Object> env;
+		public String projectName;
 
 		VsCodeConfiguration(RunConfig runConfig) {
 			this.name = runConfig.configName;
@@ -106,6 +110,8 @@ public class GenVsCodeProjectTask extends AbstractLoomTask {
 			this.vmArgs = RunConfig.joinArguments(runConfig.vmArgs);
 			this.args = RunConfig.joinArguments(runConfig.programArgs);
 			this.cwd = "${workspaceFolder}/" + runConfig.runDir;
+			this.env = new HashMap<>(runConfig.environmentVariables);
+			this.projectName = runConfig.projectName;
 
 			if (getProject().getRootProject() != getProject()) {
 				Path rootPath = getProject().getRootDir().toPath();

src/main/resources/eclipse_run_config_template.xml

@@ -6,6 +6,9 @@
     <listAttribute key="org.eclipse.debug.core.MAPPED_RESOURCE_TYPES">
         <listEntry value="4"/>
     </listAttribute>
+    <mapAttribute key="org.eclipse.debug.core.environmentVariables">
+        %ECLIPSE_ENV_VARS%
+    </mapAttribute>
     <booleanAttribute key="org.eclipse.jdt.launching.ATTR_USE_START_ON_FIRST_THREAD" value="true"/>
     <stringAttribute key="org.eclipse.jdt.launching.CLASSPATH_PROVIDER" value="org.eclipse.buildship.core.classpathprovider"/>
     <stringAttribute key="org.eclipse.jdt.launching.MAIN_TYPE" value="%MAIN_CLASS%"/>

src/main/resources/idea_run_config_template.xml

@@ -8,5 +8,8 @@
     <method v="2">
       <option name="Make" enabled="true" />
     </method>
+    <envs>
+      %IDEA_ENV_VARS%
+    </envs>
   </configuration>
 </component>