Remove the need for intermediate .zip file in PackageSupplier

By using a different overload of `retryDownload`,
we return the data instead of writing to disk,
ensuring that we don't have a lingering file
in memory and reducing IO.

This follow the same approach for deprecations as previous
`PackageSupplier` deprecations: it's an inevitable, but
easily fixable, breaking change for classes that implement
`PackageSupplier`, but it's a proper deprecation for client
code, based on the assumption that all the classes implementing
`PackageSupplier` are in Dub.

source/dub/dub.d

@@ -1021,13 +1021,11 @@ class Dub {
 		{
 			import std.zip : ZipException;
 
-			auto path = getTempFile(name.main.toString(), ".zip");
-			supplier.fetchPackage(path, name.main, range, (options & FetchOptions.usePrerelease) != 0); // Q: continue on fail?
-			scope(exit) removeFile(path);
+			auto data = supplier.fetchPackage(name.main, range, (options & FetchOptions.usePrerelease) != 0); // Q: continue on fail?
 			logDiagnostic("Placing to %s...", location.toString());
 
 			try {
-				return m_packageManager.store(path, location, name.main, ver);
+				return m_packageManager.store(data, location, name.main, ver);
 			} catch (ZipException e) {
 				logInfo("Failed to extract zip archive for %s@%s...", name, ver);
 				// re-throw the exception at the end of the loop

source/dub/packagemanager.d

@@ -738,7 +738,9 @@ class PackageManager {
 	deprecated("Use `store(NativePath source, PlacementLocation dest, string name, Version vers)`")
 	Package storeFetchedPackage(NativePath zip_file_path, Json package_info, NativePath destination)
 	{
-		return this.store_(zip_file_path, destination,
+		import dub.internal.vibecompat.core.file;
+
+		return this.store_(readFile(zip_file_path), destination,
 			PackageName(package_info["name"].get!string),
 			Version(package_info["version"].get!string));
 	}
@@ -776,6 +778,16 @@ class PackageManager {
 	{
 		import dub.internal.vibecompat.core.file;
 
+		auto data = readFile(src);
+		return this.store(data, dest, name, vers);
+	}
+
+	/// Ditto
+	Package store(ubyte[] data, PlacementLocation dest,
+		in PackageName name, in Version vers)
+	{
+		import dub.internal.vibecompat.core.file;
+
 		assert(!name.sub.length, "Cannot store a subpackage, use main package instead");
 		NativePath dstpath = this.getPackagePath(dest, name, vers.toString());
 		ensureDirectory(dstpath.parentPath());
@@ -787,26 +799,25 @@ class PackageManager {
 		if (dstpath.existsFile()) {
 			return this.getPackage(name, vers, dest);
 		}
-		return this.store_(src, dstpath, name, vers);
+		return this.store_(data, dstpath, name, vers);
 	}
 
 	/// Backward-compatibility for deprecated overload, simplify once `storeFetchedPatch`
 	/// is removed
-	private Package store_(NativePath src, NativePath destination,
+	private Package store_(ubyte[] data, NativePath destination,
 		in PackageName name, in Version vers)
 	{
 		import dub.internal.vibecompat.core.file;
 		import std.range : walkLength;
 
-		logDebug("Placing package '%s' version '%s' to location '%s' from file '%s'",
-			name, vers, destination.toNativeString(), src.toNativeString());
+		logDebug("Placing package '%s' version '%s' to location '%s'",
+			name, vers, destination.toNativeString());
 
 		enforce(!existsFile(destination),
 			"%s (%s) needs to be removed from '%s' prior placement."
 			.format(name, vers, destination));
 
-		logDebug("Opening file %s", src);
-		ZipArchive archive = new ZipArchive(readFile(src));
+		ZipArchive archive = new ZipArchive(data);
 		logDebug("Extracting from zip.");
 
 		// In a GitHub zip, the actual contents are in a sub-folder

source/dub/packagesuppliers/fallback.d

@@ -29,7 +29,7 @@ package abstract class AbstractFallbackPackageSupplier : PackageSupplier
 
 	// Workaround https://issues.dlang.org/show_bug.cgi?id=2525
 	abstract override Version[] getVersions(in PackageName name);
-	abstract override void fetchPackage(in NativePath path, in PackageName name, in VersionRange dep, bool pre_release);
+	abstract override ubyte[] fetchPackage(in PackageName name, in VersionRange dep, bool pre_release);
 	abstract override Json fetchPackageRecipe(in PackageName name, in VersionRange dep, bool pre_release);
 	abstract override SearchResult[] searchPackages(string query);
 }

source/dub/packagesuppliers/filesystem.d

@@ -44,15 +44,14 @@ class FileSystemPackageSupplier : PackageSupplier {
 		return ret;
 	}
 
-	override void fetchPackage(in NativePath path, in PackageName name,
+	override ubyte[] fetchPackage(in PackageName name,
 		in VersionRange dep, bool pre_release)
 	{
-		import dub.internal.vibecompat.core.file : copyFile, existsFile;
-		enforce(path.absolute);
+		import dub.internal.vibecompat.core.file : readFile, existsFile;
 		logInfo("Storing package '%s', version requirements: %s", name.main, dep);
 		auto filename = bestPackageFile(name, dep, pre_release);
 		enforce(existsFile(filename));
-		copyFile(filename, path);
+		return readFile(filename);
 	}
 
 	override Json fetchPackageRecipe(in PackageName name, in VersionRange dep,

source/dub/packagesuppliers/maven.d

@@ -47,21 +47,20 @@ class MavenRegistryPackageSupplier : PackageSupplier {
 		return ret;
 	}
 
-	override void fetchPackage(in NativePath path, in PackageName name,
+	override ubyte[] fetchPackage(in PackageName name,
 		in VersionRange dep, bool pre_release)
 	{
 		import std.format : format;
 		auto md = getMetadata(name.main);
 		Json best = getBestPackage(md, name.main, dep, pre_release);
 		if (best.type == Json.Type.null_)
-			return;
+			return null;
 		auto vers = best["version"].get!string;
 		auto url = m_mavenUrl ~ NativePath(
 			"%s/%s/%s-%s.zip".format(name.main, vers, name.main, vers));
 
 		try {
-			retryDownload(url, path, 3, httpTimeout);
-			return;
+			return retryDownload(url, 3, httpTimeout);
 		}
 		catch(HTTPStatusException e) {
 			if (e.status == 404) throw e;

source/dub/packagesuppliers/packagesupplier.d

@@ -32,17 +32,25 @@ interface PackageSupplier {
 	Version[] getVersions(in PackageName name);
 
 
-	/** Downloads a package and stores it as a ZIP file.
+	/** Downloads a package and returns its binary content
 
 		Params:
-			path = Absolute path of the target ZIP file
 			name = Name of the package to retrieve
 			dep = Version constraint to match against
 			pre_release = If true, matches the latest pre-release version.
 				Otherwise prefers stable versions.
 	*/
-	void fetchPackage(in NativePath path, in PackageName name,
-		in VersionRange dep, bool pre_release);
+	ubyte[] fetchPackage(in PackageName name, in VersionRange dep,
+		bool pre_release);
+
+	deprecated("Use `writeFile(path, fetchPackage(PackageName, VersionRange, bool))` instead")
+	final void fetchPackage(in NativePath path, in PackageName name,
+		in VersionRange dep, bool pre_release)
+	{
+		import dub.internal.vibecompat.core.file : writeFile;
+		if (auto res = this.fetchPackage(name, dep, pre_release))
+			writeFile(path, res);
+	}
 
     deprecated("Use `fetchPackage(NativePath, PackageName, VersionRange, bool)` instead")
 	final void fetchPackage(NativePath path, string name, Dependency dep, bool pre_release)

source/dub/packagesuppliers/registry.d

@@ -66,17 +66,15 @@ class RegistryPackageSupplier : PackageSupplier {
 		return ret;
 	}
 
-	override void fetchPackage(in NativePath path, in PackageName name,
+	override ubyte[] fetchPackage(in PackageName name,
 		in VersionRange dep, bool pre_release)
 	{
 		import std.format : format;
 
 		auto url = genPackageDownloadUrl(name, dep, pre_release);
-		if(url.isNull)
-			return;
+		if(url.isNull) return null;
 		try {
-			retryDownload(url.get, path);
-			return;
+			return retryDownload(url.get);
 		}
 		catch(HTTPStatusException e) {
 			if (e.status == 404) throw e;

source/dub/test/base.d

@@ -501,7 +501,7 @@ public class MockPackageSupplier : PackageSupplier
     }
 
     ///
-    public override void fetchPackage(in NativePath path, in PackageName name,
+    public override ubyte[] fetchPackage(in PackageName name,
         in VersionRange dep, bool pre_release)
     {
         assert(0, "%s - fetchPackage not implemented for: %s"