Don't fail setup if a project FMJ is invalid.

src/main/java/net/fabricmc/loom/util/fmj/FabricModJsonFactory.java

@@ -36,9 +36,12 @@ import java.nio.file.Path;
 import java.util.Optional;
 
 import com.google.gson.JsonObject;
+import com.google.gson.JsonSyntaxException;
 import org.gradle.api.tasks.SourceSet;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.annotations.VisibleForTesting;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import net.fabricmc.loom.LoomGradlePlugin;
 import net.fabricmc.loom.util.FileSystemUtil;
@@ -48,6 +51,8 @@ import net.fabricmc.loom.util.gradle.SourceSetHelper;
 public final class FabricModJsonFactory {
 	public static final String FABRIC_MOD_JSON = "fabric.mod.json";
 
+	private static final Logger LOGGER = LoggerFactory.getLogger(FabricModJsonFactory.class);
+
 	private FabricModJsonFactory() {
 	}
 
@@ -115,6 +120,11 @@ public final class FabricModJsonFactory {
 
 		try (Reader reader = Files.newBufferedReader(file.toPath(), StandardCharsets.UTF_8)) {
 			return create(LoomGradlePlugin.GSON.fromJson(reader, JsonObject.class), new FabricModJsonSource.SourceSetSource(sourceSets));
+		} catch (JsonSyntaxException e) {
+			LOGGER.warn("Failed to parse fabric.mod.json: {}", file.getAbsolutePath());
+			return null;
+		} catch (IOException e) {
+			throw new UncheckedIOException("Failed to read " + file.getAbsolutePath(), e);
 		}
 	}
 

src/test/groovy/net/fabricmc/loom/test/integration/DataGenerationTest.groovy

@@ -88,7 +88,7 @@ class DataGenerationTest extends Specification implements GradleProjectTestTrait
 
                     modDatagenImplementation fabricApi.module("fabric-data-generation-api-v1", "0.90.0+1.20.2")
                 }
-                
+
                 println("%%" + loom.runs.datagen.configName + "%%")
             '''
 		when: