Exclude client only libraries in the IntelliJ server run config.

src/main/java/net/fabricmc/loom/configuration/ide/idea/IdeaSyncTask.java

@@ -26,17 +26,33 @@ package net.fabricmc.loom.configuration.ide.idea;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.StringReader;
+import java.io.StringWriter;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Set;
 
 import javax.inject.Inject;
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.transform.OutputKeys;
+import javax.xml.transform.Transformer;
+import javax.xml.transform.TransformerFactory;
+import javax.xml.transform.dom.DOMSource;
+import javax.xml.transform.stream.StreamResult;
 
 import org.apache.commons.io.FileUtils;
 import org.gradle.api.Project;
 import org.gradle.api.tasks.TaskAction;
+import org.jetbrains.annotations.VisibleForTesting;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.NodeList;
+import org.xml.sax.InputSource;
 
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.configuration.ide.RunConfig;
@@ -95,7 +111,7 @@ public abstract class IdeaSyncTask extends AbstractLoomTask {
 
 			if (settings.getEnvironment().equals("server") && !excludedServerLibraries.isEmpty()) {
 				try {
-					setClasspathModifications(runConfigs, excludedServerLibraries);
+					setClasspathModifications(runConfigs.toPath(), excludedServerLibraries);
 				} catch (Exception e) {
 					getProject().getLogger().error("Failed to modify run configuration xml", e);
 				}
@@ -124,7 +140,67 @@ public abstract class IdeaSyncTask extends AbstractLoomTask {
 		return clientOnlyLibraries;
 	}
 
-	private void setClasspathModifications(File runConfig, List<String> exclusions) throws Exception {
+	private void setClasspathModifications(Path runConfig, List<String> exclusions) throws IOException {
-		// TODO modify the xml
+		if (!IdeaUtils.supportsCustomizableClasspath()) {
+			return;
+		}
+
+		final String inputXml = Files.readString(runConfig, StandardCharsets.UTF_8);
+		final String outputXml;
+
+		try {
+			outputXml = setClasspathModificationsInXml(inputXml, exclusions);
+		} catch (Exception e) {
+			getLogger().error("Failed to modify idea xml", e);
+
+			return;
+		}
+
+		if (!inputXml.equals(outputXml)) {
+			Files.writeString(runConfig, outputXml, StandardCharsets.UTF_8);
+		}
+	}
+
+	@VisibleForTesting
+	public static String setClasspathModificationsInXml(String input, List<String> exclusions) throws Exception {
+		final DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
+		final DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
+		final Document document = documentBuilder.parse(new InputSource(new StringReader(input)));
+		final Element root = document.getDocumentElement();
+
+		final NodeList nodeList = root.getElementsByTagName("configuration");
+		assert nodeList.getLength() == 1;
+
+		final Element configuration = (Element) nodeList.item(0);
+		final NodeList classpathModificationsList = configuration.getElementsByTagName("classpathModifications");
+
+		// Remove all the existing exclusions
+		for (int i = 0; i < classpathModificationsList.getLength(); i++) {
+			configuration.removeChild(classpathModificationsList.item(i));
+		}
+
+		final Element classpathModifications = document.createElement("classpathModifications");
+
+		for (String exclusionPath : exclusions) {
+			final Element exclusion = document.createElement("entry");
+
+			exclusion.setAttribute("exclude", "true");
+			exclusion.setAttribute("path", exclusionPath);
+
+			classpathModifications.appendChild(exclusion);
+		}
+
+		configuration.appendChild(classpathModifications);
+
+		final TransformerFactory transformerFactory = TransformerFactory.newInstance();
+		final Transformer transformer = transformerFactory.newTransformer();
+		transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
+
+		final DOMSource source = new DOMSource(document);
+
+		final StringWriter writer = new StringWriter();
+		transformer.transform(source, new StreamResult(writer));
+
+		return writer.toString().replace("\r", "");
 	}
 }

src/test/groovy/net/fabricmc/loom/test/unit/IdeaClasspathModificationsTest.groovy

@@ -0,0 +1,104 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.test.unit
+
+import net.fabricmc.loom.configuration.ide.RunConfig
+import net.fabricmc.loom.configuration.ide.idea.IdeaSyncTask
+import org.intellij.lang.annotations.Language
+import spock.lang.Specification
+
+import java.nio.charset.StandardCharsets
+
+class IdeaClasspathModificationsTest extends Specification {
+
+    def "configure exclusions"() {
+        when:
+            def input = fromDummy()
+            def output = IdeaSyncTask.setClasspathModificationsInXml(input, ["/path/to/file.jar"])
+
+        then:
+            output == EXPECTED
+    }
+
+    def "re-configure exclusions"() {
+        when:
+            def input = fromDummy()
+            def output = IdeaSyncTask.setClasspathModificationsInXml(input, ["/path/to/file.jar"])
+            output = IdeaSyncTask.setClasspathModificationsInXml(output, ["/path/to/file.jar", "/path/to/another.jar"])
+
+        then:
+            output == EXPECTED2
+    }
+
+    private String fromDummy() {
+        String dummyConfig
+
+        IdeaSyncTask.class.getClassLoader().getResourceAsStream("idea_run_config_template.xml").withCloseable {
+            dummyConfig = new String(it.readAllBytes(), StandardCharsets.UTF_8)
+        }
+
+        dummyConfig = dummyConfig.replace("%NAME%", "Minecraft Client")
+        dummyConfig = dummyConfig.replace("%MAIN_CLASS%", "net.minecraft.client.Main")
+        dummyConfig = dummyConfig.replace("%IDEA_MODULE%", "main.test")
+        dummyConfig = dummyConfig.replace("%RUN_DIRECTORY%", ".run")
+        dummyConfig = dummyConfig.replace("%PROGRAM_ARGS%", RunConfig.joinArguments([]).replaceAll("\"", """))
+        dummyConfig = dummyConfig.replace("%VM_ARGS%", RunConfig.joinArguments([]).replaceAll("\"", """))
+
+        return dummyConfig
+    }
+
+    @Language("XML")
+    private static final String EXPECTED = '''
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" factoryName="Application" name="Minecraft Client" type="Application">
+    <option name="MAIN_CLASS_NAME" value="net.minecraft.client.Main"/>
+    <module name="main.test"/>
+    <option name="PROGRAM_PARAMETERS" value=""/>
+    <option name="VM_PARAMETERS" value=""/>
+    <option name="WORKING_DIRECTORY" value="$PROJECT_DIR$/.run/"/>
+    <method v="2">
+      <option enabled="true" name="Make"/>
+    </method>
+  <classpathModifications><entry exclude="true" path="/path/to/file.jar"/></classpathModifications></configuration>
+</component>
+'''.trim()
+
+    @Language("XML")
+    private static final String EXPECTED2 = '''
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" factoryName="Application" name="Minecraft Client" type="Application">
+    <option name="MAIN_CLASS_NAME" value="net.minecraft.client.Main"/>
+    <module name="main.test"/>
+    <option name="PROGRAM_PARAMETERS" value=""/>
+    <option name="VM_PARAMETERS" value=""/>
+    <option name="WORKING_DIRECTORY" value="$PROJECT_DIR$/.run/"/>
+    <method v="2">
+      <option enabled="true" name="Make"/>
+    </method>
+  <classpathModifications><entry exclude="true" path="/path/to/file.jar"/><entry exclude="true" path="/path/to/another.jar"/></classpathModifications></configuration>
+</component>
+'''.trim()
+
+}