Fix Loader#name to show the file name in exception message (#279)

Author: tom-tan

source/dyaml/loader.d

@@ -165,6 +165,7 @@ struct Loader
         void name(string name) pure @safe nothrow @nogc
         {
             name_ = name;
+            scanner_.name = name;
         }
 
         /// Specify custom Resolver to use.
@@ -392,3 +393,19 @@ struct Loader
     auto doc = Loader.fromString(yaml).load();
     assert(doc.isValid);
 }
+
+@safe unittest
+{
+    import std.exception : collectException;
+
+    auto yaml = q"EOS
+    value: invalid: string
+EOS";
+    auto filename = "invalid.yml";
+    auto loader = Loader.fromString(yaml);
+    loader.name = filename;
+
+    Node unused;
+    auto e = loader.load().collectException!ScannerException(unused);
+    assert(e.mark.name == filename);
+}

source/dyaml/reader.d

@@ -405,6 +405,9 @@ final class Reader
         /// Get file name.
         string name() const @safe pure nothrow @nogc { return name_; }
 
+        /// Set file name.
+        void name(string name) pure @safe nothrow @nogc { name_ = name; }
+
         /// Get current line number.
         uint line() const @safe pure nothrow @nogc { return line_; }
 

source/dyaml/scanner.d

@@ -185,6 +185,12 @@ struct Scanner
             return tokens_.empty;
         }
 
+        /// Set file name.
+        void name(string name) @safe pure nothrow @nogc
+        {
+            reader_.name = name;
+        }
+
     private:
         /// Most scanning error messages have the same format; so build them with this
         /// function.