Some minor peformance improvements.

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

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2021-2022 FabricMC
+ * Copyright (c) 2021-2024 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
@@ -124,12 +124,9 @@ private void setupPreparationTask() {
 		mustRunAfter(prepareJarTask);
 
 		getProject().getGradle().allprojects(project -> {
-			project.getTasks().configureEach(task -> {
-				if (task instanceof PrepareJarRemapTask otherTask) {
-					// Ensure that all remap jars run after all prepare tasks
-					mustRunAfter(otherTask);
-				}
-			});
+			project.getTasks()
+					.withType(PrepareJarRemapTask.class)
+					.configureEach(this::mustRunAfter);
 		});
 	}
 

src/main/java/net/fabricmc/loom/util/download/Download.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2022 FabricMC
+ * Copyright (c) 2022-2024 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
@@ -43,7 +43,6 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
-import java.nio.file.attribute.BasicFileAttributeView;
 import java.nio.file.attribute.FileTime;
 import java.time.Duration;
 import java.time.Instant;
@@ -191,6 +190,13 @@ private void doDownload(Path output) throws DownloadException {
 		boolean success = statusCode == HttpURLConnection.HTTP_NOT_MODIFIED || (statusCode >= 200 && statusCode < 300);
 
 		if (statusCode == HttpURLConnection.HTTP_NOT_MODIFIED) {
+			try {
+				// Update the last modified time so we don't retry the request until the max age has passed again.
+				Files.setLastModifiedTime(output, FileTime.from(Instant.now()));
+			} catch (IOException e) {
+				throw error(e, "Failed to update last modified time");
+			}
+
 			// Success, etag matched.
 			return;
 		}
@@ -365,9 +371,9 @@ private boolean isHashValid(Path path) {
 
 	private boolean isOutdated(Path path) throws DownloadException {
 		try {
-			final FileTime lastModified = getLastModified(path);
-			return lastModified.toInstant().plus(maxAge)
-					.isBefore(Instant.now());
+			final FileTime lastModified = Files.getLastModifiedTime(path);
+			return lastModified.toInstant()
+					.isBefore(Instant.now().minus(maxAge));
 		} catch (IOException e) {
 			throw error(e, "Failed to check if (%s) is outdated", path);
 		}
@@ -430,11 +436,6 @@ private static boolean exists(Path path) {
 		return path.getFileSystem() == FileSystems.getDefault() ? path.toFile().exists() : Files.exists(path);
 	}
 
-	private FileTime getLastModified(Path path) throws IOException {
-		final BasicFileAttributeView basicView = Files.getFileAttributeView(path, BasicFileAttributeView.class);
-		return basicView.readAttributes().lastModifiedTime();
-	}
-
 	private Path getLockFile(Path output) {
 		return output.resolveSibling(output.getFileName() + ".lock");
 	}

src/test/groovy/net/fabricmc/loom/test/benchmark/FabricAPIBenchmark.groovy

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2022 FabricMC
+ * Copyright (c) 2022-2024 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
@@ -44,12 +44,20 @@ class FabricAPIBenchmark implements GradleProjectTestTrait {
 				allowExistingRepo: true,
 
 				repo: "https://github.com/FabricMC/fabric.git",
-				commit: "2facd446984085376bd23245410ebf2dc0881b02",
+				commit: "efa5891941a32589207dc58c2e77183d599465b8",
 				patch: "fabric_api"
 				)
 
 		gradle.enableMultiProjectOptimisation()
 
+		if (!gradle.buildGradle.text.contains("loom.mixin.useLegacyMixinAp")) {
+			gradle.buildGradle << """
+				allprojects {
+					loom.mixin.useLegacyMixinAp = false
+				}
+				""".stripIndent()
+		}
+
 		def timeStart = new Date()
 
 		def result = gradle.run(tasks: [

src/test/groovy/net/fabricmc/loom/test/unit/download/DownloadFileTest.groovy

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2022 FabricMC
+ * Copyright (c) 2022-2024 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
@@ -234,6 +234,52 @@ class DownloadFileTest extends DownloadTest {
 		requestCount == 1
 	}
 
+	def "ETag with max age"() {
+		setup:
+		// The count of requests, can return early if the ETag matches.
+		int requestCount = 0
+		// The count of full downloads
+		int downloadCount = 0
+
+		server.get("/etag") {
+			def clientEtag = it.req.getHeader("If-None-Match")
+
+			def result = "Hello world"
+			def etag = result.hashCode().toString()
+			it.header("ETag", etag)
+
+			requestCount ++
+
+			if (clientEtag == etag) {
+				// Etag matches, no need to send the data.
+				it.status(HttpStatus.NOT_MODIFIED)
+				return
+			}
+
+			it.result(result)
+			downloadCount ++
+		}
+
+		def output = new File(File.createTempDir(), "etag.txt").toPath()
+
+		when:
+		for (i in 0..<3) {
+			if (i == 2) {
+				// On the third request, set the file to be 2 days old, forcing the etag to be checked.
+				Files.setLastModifiedTime(output, FileTime.from(Instant.now() - Duration.ofDays(2)))
+			}
+
+			Download.create("$PATH/etag")
+					.etag(true)
+					.maxAge(Duration.ofDays(1))
+					.downloadPath(output)
+		}
+
+		then:
+		requestCount == 2
+		downloadCount == 1
+	}
+
 	def "Progress: File"() {
 		setup:
 		server.get("/progressFile") {