Add loom.modVersion to read the version from the fabric.mod.json file.

src/main/java/net/fabricmc/loom/api/LoomGradleExtensionAPI.java

@@ -196,4 +196,12 @@ default String getCustomManifest() {
 	 */
 	@ApiStatus.Experimental
 	void disableDeprecatedPomGeneration(MavenPublication publication);
+
+	/**
+	 * Reads the mod version from the fabric.mod.json file located in the main sourcesets resources.
+	 * This is useful if you want to set the gradle version based of the version in the fabric.mod.json file.
+	 *
+	 * @return the version defined in the fabric.mod.json
+	 */
+	String getModVersion();
 }

src/main/java/net/fabricmc/loom/configuration/mods/ModVersionParser.java

@@ -0,0 +1,76 @@
+/*
+ * 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.configuration.mods;
+
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+
+import com.google.gson.JsonObject;
+import org.gradle.api.Project;
+import org.gradle.api.plugins.JavaPluginConvention;
+
+import net.fabricmc.loom.LoomGradlePlugin;
+
+public class ModVersionParser {
+	private final Project project;
+
+	private String version = null;
+
+	public ModVersionParser(Project project) {
+		this.project = project;
+	}
+
+	public String getModVersion() {
+		if (version != null) {
+			return version;
+		}
+
+		File json = locateModJsonFile();
+		JsonObject jsonObject;
+
+		try (var reader = new FileReader(json)) {
+			jsonObject = LoomGradlePlugin.GSON.fromJson(reader, JsonObject.class);
+		} catch (IOException e) {
+			throw new RuntimeException("Failed to read fabric.mod.json file");
+		}
+
+		if (!jsonObject.has("version") || !jsonObject.get("version").isJsonPrimitive()) {
+			throw new UnsupportedOperationException("Could not find valid version in the fabric.mod.json file");
+		}
+
+		version = jsonObject.get("version").getAsString();
+
+		return version;
+	}
+
+	private File locateModJsonFile() {
+		return project.getConvention().getPlugin(JavaPluginConvention.class).getSourceSets()
+				.getByName("main")
+				.getResources()
+				.matching(patternFilterable -> patternFilterable.include("fabric.mod.json"))
+				.getSingleFile();
+	}
+}

src/main/java/net/fabricmc/loom/extension/LoomGradleExtensionApiImpl.java

@@ -38,6 +38,7 @@
 import net.fabricmc.loom.api.MixinExtensionAPI;
 import net.fabricmc.loom.api.decompilers.LoomDecompiler;
 import net.fabricmc.loom.configuration.ide.RunConfigSettings;
+import net.fabricmc.loom.configuration.mods.ModVersionParser;
 import net.fabricmc.loom.configuration.processors.JarProcessor;
 import net.fabricmc.loom.configuration.providers.mappings.GradleMappingContext;
 import net.fabricmc.loom.configuration.providers.mappings.LayeredMappingSpec;
@@ -59,6 +60,8 @@ public abstract class LoomGradleExtensionApiImpl implements LoomGradleExtensionA
 	protected final Property<String> customManifest;
 	protected final Property<Boolean> setupRemappedVariants;
 
+	private final ModVersionParser versionParser;
+
 	private NamedDomainObjectContainer<RunConfigSettings> runConfigs;
 
 	protected LoomGradleExtensionApiImpl(Project project, LoomFiles directories) {
@@ -78,6 +81,8 @@ protected LoomGradleExtensionApiImpl(Project project, LoomFiles directories) {
 		this.setupRemappedVariants = project.getObjects().property(Boolean.class)
 				.convention(true);
 
+		this.versionParser = new ModVersionParser(project);
+
 		this.deprecationHelper = new DeprecationHelper.ProjectBased(project);
 	}
 
@@ -149,6 +154,11 @@ public Property<Boolean> getSetupRemappedVariants() {
 		return setupRemappedVariants;
 	}
 
+	@Override
+	public String getModVersion() {
+		return versionParser.getModVersion();
+	}
+
 	protected abstract Project getProject();
 
 	protected abstract LoomFiles getFiles();

src/main/java/net/fabricmc/loom/extension/MinecraftGradleExtension.java

@@ -144,4 +144,10 @@ public void disableDeprecatedPomGeneration(MavenPublication publication) {
 		reportDeprecation();
 		parent.disableDeprecatedPomGeneration(publication);
 	}
+
+	@Override
+	public String getModVersion() {
+		reportDeprecation();
+		throw new UnsupportedOperationException("Use loom extension");
+	}
 }

src/test/resources/projects/simple/build.gradle

@@ -7,7 +7,7 @@ sourceCompatibility = JavaVersion.VERSION_1_8
 targetCompatibility = JavaVersion.VERSION_1_8
 
 archivesBaseName = project.archives_base_name
-version = project.mod_version
+version = loom.modVersion
 group = project.maven_group
 
 repositories {
@@ -31,14 +31,6 @@ dependencies {
 	// You may need to force-disable transitiveness on them.
 }
 
-processResources {
-	inputs.property "version", project.version
-
-	filesMatching("fabric.mod.json") {
-		expand "version": project.version
-	}
-}
-
 tasks.withType(JavaCompile).configureEach {
 	// ensure that the encoding is set to UTF-8, no matter what the system default is
 	// this fixes some edge cases with special characters not displaying correctly

src/test/resources/projects/simple/gradle.properties

@@ -8,7 +8,6 @@ org.gradle.jvmargs=-Xmx1G
 	loader_version=0.11.2
 
 # Mod Properties
-	mod_version = 1.0.0
 	maven_group = com.example
 	archives_base_name = fabric-example-mod
 

src/test/resources/projects/simple/src/main/resources/fabric.mod.json

@@ -1,7 +1,7 @@
 {
   "schemaVersion": 1,
   "id": "modid",
-  "version": "${version}",
+  "version": "1.0.0",
 
   "name": "Example Mod",
   "description": "This is an example description! Tell everyone what your mod is about!",