Merge remote-tracking branch 'tim/master'

Author: Camotoy

format/yaml/src/main/java/org/spongepowered/configurate/yaml/YamlConfigurationLoader.java

@@ -269,7 +269,15 @@ protected void loadInternal(final CommentedConfigurationNode node, final Buffere
         // the constructor needs ConfigurationOptions for the to be created nodes
         // and since it's a thread-local, this won't cause any issues
         this.constructor.get().options = node.options();
-        node.from(this.yaml.get().load(reader));
+
+        @Nullable CommentedConfigurationNode loaded = this.yaml.get().load(reader);
+        // when a file exists but is empty (or if the file only exists of comments), the first event will be StreamEnd.
+        // getSingleNode will return null, getSingleData uses the Constructor of Tag Null, which just returns null.
+        // So we have to map null to an empty root node.
+        if (loaded == null) {
+            loaded = CommentedConfigurationNode.root(node.options());
+        }
+        node.from(loaded);
     }
 
     @Override

format/yaml/src/main/java/org/spongepowered/configurate/yaml/YamlConstructor.java

@@ -31,6 +31,7 @@
 import org.yaml.snakeyaml.nodes.NodeTuple;
 import org.yaml.snakeyaml.nodes.ScalarNode;
 import org.yaml.snakeyaml.nodes.SequenceNode;
+import org.yaml.snakeyaml.nodes.Tag;
 
 import java.util.Collection;
 import java.util.Collections;
@@ -61,6 +62,17 @@ protected Object constructObjectNoCheck(final Node yamlNode) {
         //noinspection DataFlowIssue guarenteed NonNull by getSingleData, which load(Reader) uses
         final CommentedConfigurationNode node = CommentedConfigurationNode.root(this.options);
 
+        // alright, let's first check some interesting behaviour.
+        // When you have a file with only empty lines (has to be at least two),
+        // a Tag of the type COMMENT will be executed.
+        // It'll have a blockComment of the type empty line.
+        // This is unlike the behaviour of an empty file and a file with only comments,
+        // because both won't be seen as an object and will instead return null by Yaml#load.
+        // Let's filter out the multi-empty-lines behaviour and return an empty node instead.
+        if (yamlNode.getTag() == Tag.COMMENT) {
+            return node;
+        }
+
         if (yamlNode.getNodeId() == NodeId.mapping) {
             // make sure to mark it as a map type, even if the map itself is empty
             node.raw(Collections.emptyMap());

format/yaml/src/test/java/org/spongepowered/configurate/yaml/YamlConfigurationLoaderTest.java

@@ -35,6 +35,7 @@
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -108,6 +109,57 @@ void testWriteBasicFile(final @TempDir Path tempDir) throws IOException {
         assertContentsSame(this.resource("write-expected.yml"), target);
     }
 
+    @Test
+    void testNonExistentFile() throws IOException {
+        final Path path = Paths.get("non-existent-file.yml");
+        final YamlConfigurationLoader loader = YamlConfigurationLoader.builder().path(path).build();
+
+        final ConfigurationNode actual = loader.load();
+        assertEquals(CommentedConfigurationNode.root(), actual);
+    }
+
+    @Test
+    void testEmptyFile(final @TempDir Path tempDir) throws IOException {
+        // an empty file should be seen as empty node, by default SnakeYaml returns null for loading an empty file.
+        // Check if it correctly gets mapped to an empty node.
+
+        // Configurate's Spotless settings require an empty row after the last row (so essentially making the file
+        // multiline), to bypass this we write an empty temp file and read that.
+        final Path emptyFile = tempDir.resolve("empty-file.yml");
+        Files.write(emptyFile, Collections.emptyList());
+
+        final YamlConfigurationLoader loader = YamlConfigurationLoader.builder().path(emptyFile).build();
+
+        final ConfigurationNode actual = loader.load();
+        assertEquals(CommentedConfigurationNode.root(), actual);
+    }
+
+    @Test
+    void testEmptyFileMultiline() throws IOException {
+        // a multiline file has at least some data (the fact that it has multiple lines), which is why it's handled
+        // differently inside SnakeYaml. This is seen as a mapping node with the Tag COMMENT.
+
+        final URL url = this.resource("no-data-multiline.yml");
+        final YamlConfigurationLoader loader = YamlConfigurationLoader.builder().url(url).build();
+
+        final ConfigurationNode actual = loader.load();
+        assertEquals(CommentedConfigurationNode.root(), actual);
+    }
+
+    @Test
+    void testEmptyFileOnlyComments() throws IOException {
+        // just like 'empty file' and 'empty file multiline', this is kind of a weird situation.
+        // In SnakeYaml, when the file exists of just comments, the first event will be StreamEnd.
+        // getSingleNode will return null, getSingleData uses the Constructor of Tag Null, which just returns null.
+        // Make sure that we return an empty node there.
+
+        final URL url = this.resource("no-data-just-comments.yml");
+        final YamlConfigurationLoader loader = YamlConfigurationLoader.builder().url(url).build();
+
+        final ConfigurationNode actual = loader.load();
+        assertEquals(CommentedConfigurationNode.root(), actual);
+    }
+
     @Test
     void testReadComments() throws IOException {
         final ConfigurationNode expected = CommentedConfigurationNode.root(n ->
@@ -123,8 +175,7 @@ void testReadComments() throws IOException {
                 ));
 
         final URL url = this.resource("comments-test.yml");
-        final YamlConfigurationLoader loader = YamlConfigurationLoader.builder()
-            .url(url).build();
+        final YamlConfigurationLoader loader = YamlConfigurationLoader.builder().url(url).build();
 
         final ConfigurationNode actual = loader.load();
         assertEquals(expected, actual);

format/yaml/src/test/resources/org/spongepowered/configurate/yaml/no-data-just-comments.yml

@@ -0,0 +1,2 @@
+# hello
+# what

format/yaml/src/test/resources/org/spongepowered/configurate/yaml/no-data-multiline.yml

@@ -0,0 +1 @@
+