Deprecate Package.load, use PackageManager.load instead

In order for the dependency injection approach to work,
we need to be able to override every single instance of
`Package.load`. We could not override `Package.load` itself
as it is a static function.
However, in the process of adding support for path-based dependencies
to the test suite, it became obvious that the functionality offered
by `Package.load` is actually better suited for the `PackageManager`.
Deprecating `Package.load` confirms this: Not a single call was outside
of `PackageManager`, and no extra parameter had to be provided anywhere
to make this work.
This also nicely simplifies the `TestPackageManager` implementation,
as we can now overload `load` and let `getPackage` alone.

source/dub/package_.d

@@ -80,9 +80,10 @@ static immutable string[] builtinBuildTypes = [
 /**	Represents a package, including its sub packages.
 */
 class Package {
+	// `package` visibility as it is set from the PackageManager
+	package NativePath m_infoFile;
 	private {
 		NativePath m_path;
-		NativePath m_infoFile;
 		PackageRecipe m_info;
 		PackageRecipe m_rawRecipe;
 		Package m_parentPackage;
@@ -173,6 +174,7 @@ class Package {
 				determined by invoking the VCS (GIT currently).
 			mode = Whether to issue errors, warning, or ignore unknown keys in dub.json
 	*/
+	deprecated("Use `PackageManager.getOrLoadPackage` instead of loading packages directly")
 	static Package load(NativePath root, NativePath recipe_file = NativePath.init,
 		Package parent = null, string version_override = "",
 		StrictMode mode = StrictMode.Ignore)

source/dub/packagemanager.d

@@ -332,11 +332,54 @@ class PackageManager {
 		foreach (p; this.m_internal.fromPath)
 			if (p.path == path && (!p.parentPackage || (allow_sub_packages && p.parentPackage.path != p.path)))
 				return p;
-		auto pack = Package.load(path, recipe_path, null, null, mode);
+		auto pack = this.load(path, recipe_path, null, null, mode);
 		addPackages(this.m_internal.fromPath, pack);
 		return pack;
 	}
 
+	/**
+	 * Loads a `Package` from the filesystem
+	 *
+	 * This is called when a `Package` needs to be loaded from the path.
+	 * This does not change the internal state of the `PackageManager`,
+	 * it simply loads the `Package` and returns it - it is up to the caller
+	 * to call `addPackages`.
+	 *
+	 * Throws:
+	 *   If no package can be found at the `path` / with the `recipe`.
+	 *
+	 * Params:
+	 *     path = The directory in which the package resides.
+	 *     recipe = Optional path to the package recipe file. If left empty,
+	 *              the `path` directory will be searched for a recipe file.
+	 *     parent = Reference to the parent package, if the new package is a
+	 *              sub package.
+	 *     version_ = Optional version to associate to the package instead of
+	 *                the one declared in the package recipe, or the one
+	 *                determined by invoking the VCS (GIT currently).
+	 *     mode = Whether to issue errors, warning, or ignore unknown keys in
+	 *            dub.json
+	 *
+	 * Returns: A populated `Package`.
+	 */
+	protected Package load(NativePath path, NativePath recipe = NativePath.init,
+		Package parent = null, string version_ = null,
+		StrictMode mode = StrictMode.Ignore) const
+	{
+		if (recipe.empty)
+			recipe = Package.findPackageFile(path);
+
+		enforce(!recipe.empty,
+			"No package file found in %s, expected one of %s"
+				.format(path.toNativeString(),
+					packageInfoFiles.map!(f => cast(string)f.filename).join("/")));
+
+		auto content = readPackageRecipe(recipe, parent ? parent.name : null, mode);
+		auto ret = new Package(content, path, parent, version_);
+		ret.m_infoFile = recipe;
+		return ret;
+	}
+
 	/** For a given SCM repository, returns the corresponding package.
 
 		An SCM repository is provided as its remote URL, the repository is cloned
@@ -399,7 +442,7 @@ class PackageManager {
 			return null;
 		}
 
-		return Package.load(destination);
+		return this.load(destination);
 	}
 
 	/**
@@ -787,7 +830,7 @@ symlink_exit:
 		logDebug("%s file(s) copied.", to!string(countFiles));
 
 		// overwrite dub.json (this one includes a version field)
-		auto pack = Package.load(destination, NativePath.init, null, vers.toString());
+		auto pack = this.load(destination, NativePath.init, null, vers.toString());
 
 		if (pack.recipePath.head != defaultPackageFilename)
 			// Storeinfo saved a default file, this could be different to the file from the zip.
@@ -850,7 +893,7 @@ symlink_exit:
 			this.refresh();
 
 		path.endsWithSlash = true;
-		auto pack = Package.load(path);
+		auto pack = this.load(path);
 		enforce(pack.name.length, "The package has no name, defined in: " ~ path.toString());
 		if (verName.length)
 			pack.version_ = Version(verName);
@@ -995,7 +1038,7 @@ symlink_exit:
 				p.normalize();
 				enforce(!p.absolute, "Sub package paths must be sub paths of the parent package.");
 				auto path = pack.path ~ p;
-				sp = Package.load(path, NativePath.init, pack);
+				sp = this.load(path, NativePath.init, pack);
 			} else sp = new Package(spr.recipe, pack.path, pack);
 
 			// Add the sub-package.
@@ -1241,7 +1284,7 @@ package struct Location {
 
 						if (!pp) {
 							auto infoFile = Package.findPackageFile(path);
-							if (!infoFile.empty) pp = Package.load(path, infoFile);
+							if (!infoFile.empty) pp = manager.load(path, infoFile);
 							else {
 								logWarn("Locally registered package %s %s was not found. Please run 'dub remove-local \"%s\"'.",
 										name, ver, path.toNativeString());
@@ -1304,7 +1347,7 @@ package struct Location {
 						p = pp;
 						break;
 					}
-				if (!p) p = Package.load(pack_path, packageFile);
+				if (!p) p = mgr.load(pack_path, packageFile);
 				mgr.addPackages(this.fromPath, p);
 			} catch (ConfigException exc) {
 				// Configy error message already include the path
@@ -1403,7 +1446,7 @@ package struct Location {
 			return null;
 
 		logDiagnostic("Lazily loading package %s:%s from %s", lookupName, vers, path);
-		auto p = Package.load(path);
+		auto p = mgr.load(path);
 		enforce(
 			p.version_ == vers,
 			format("Package %s located in %s has a different version than its path: Got %s, expected %s",

source/dub/test/base.d

@@ -289,27 +289,17 @@ package class TestPackageManager : PackageManager
         // Do nothing
     }
 
-    /**
-     * Looks up a specific package
-     *
-     * Unlike its parent class, no lazy loading is performed.
-     * Additionally, as they are already deprecated, overrides are
-     * disabled and not available.
-     */
-	public override Package getPackage(string name, Version vers, bool enable_overrides = false)
+	/**
+	 * Loads a `Package`
+	 *
+	 * This is currently not implemented, and any call to it will trigger
+	 * an assert, as that would otherwise be an access to the filesystem.
+	 */
+	protected override Package load(NativePath path, NativePath recipe = NativePath.init,
+		Package parent = null, string version_ = null,
+		StrictMode mode = StrictMode.Ignore) const
     {
-        //assert(!enable_overrides, "Overrides are not implemented for TestPackageManager");
-
-        // Implementation inspired from `PackageManager.lookup`,
-        // except we replaced `load` with `lookup`.
-        if (auto pkg = this.m_internal.lookup(name, vers, this))
-			return pkg;
-
-		foreach (ref location; this.m_repositories)
-			if (auto p = location.lookup(name, vers, this))
-				return p;
-
-		return null;
+        assert(0, "`TestPackageManager.load` is not implemented");
     }
 
 	/**