Added a getPackageNames function to the PackageSupplier interface, an…

…d an implementation for the RegistryPackageSupplier. Currently, FileSystemPackageSupplier.getPackageNames is not implemented.

The catch block of Dub.createEmptyPackage() now uses this and tries to find close matches to what the user entered.
Currently, "close matches" are defined as anything with a levenshteinDistance of <=4.

source/dub/dub.d

@@ -616,7 +616,18 @@ class Dub {
 					auto versionStrings = ps.getVersions(dep);
 					depVers[dep] = versionStrings[$-1].toString;
 				} catch(Exception e){
-					logError("Error, no package %s found. Ignoring...", dep);
+					auto packages = ps.getPackageNames();
+					string[][size_t] lds; //holds the levenshteinDistance from dep for each package
+					foreach(pack; packages){
+						lds[dep.levenshteinDistance(pack)] ~= pack;
+					}
+					auto closestKey = lds.keys.sort.front;
+					if(closestKey <= 4){
+						logError("Error, no package \"%s\" found. Did you mean %s?", dep, lds[closestKey]);
+					} else{
+						logError("Error, no package \"%s\" found. Exiting...", dep);
+					}
+					return;
 				}
 			}
 		}

source/dub/packagesupplier.d

@@ -41,6 +41,9 @@ interface PackageSupplier {
 
 	/// perform cache operation
 	void cacheOp(Path cacheDir, CacheOp op);
+
+	/// get all package names for this supplier
+	string[] getPackageNames();
 }
 
 /// operations on package supplier cache
@@ -92,6 +95,10 @@ class FileSystemPackageSupplier : PackageSupplier {
 	void cacheOp(Path cacheDir, CacheOp op) {
 	}
 
+	string[] getPackageNames(){
+		assert(false, "FileSystemPackageSupplier.getPackageNames, not implemented yet");
+	}
+
 	private Path bestPackageFile(string packageId, Dependency dep, bool pre_release)
 	{
 		Path toPath(Version ver) {
@@ -148,11 +155,23 @@ class RegistryPackageSupplier : PackageSupplier {
 		download(url, path);
 	}
 
+
 	Json getPackageDescription(string packageId, Dependency dep, bool pre_release)
 	{
 		return getBestPackage(packageId, dep, pre_release);
 	}
 
+	string[] getPackageNames(){
+		import std.array : replace;
+		auto url = m_registryUrl ~ Path(PackagesPath~"/index.json");
+		Json data = (cast(string)download(url)).parseJsonString();
+		string[] packages;
+		foreach(ele; data){
+			packages ~= ele.toString().replace("\"", "");
+		}
+		return packages;
+	}
+
 	void cacheOp(Path cacheDir, CacheOp op)
 	{
 		auto path = cacheDir ~ cacheFileName;