JSON5 support

buildSrc/src/main/kotlin/org/spongepowered/configurate/build/ConfigurateDevPlugin.kt

@@ -62,6 +62,8 @@ class ConfigurateDevPlugin : Plugin<Project> {
                     header = rootProject.file("LICENSE_HEADER")
                     include("**/*.java")
                     include("**/*.kt")
+                    // TODO: this is probably not very efficient
+                    exclude { it.file.absolutePath.contains("generated") }
                     newLine = false
                 }
             }

etc/checkstyle/suppressions.xml

@@ -9,4 +9,7 @@
     <suppress id="LineLengthComment" files="JacksonVisitor\.java"/> <!-- Commented out code -->
     <!-- We don't need javadoc on examples, they already go alongside documentation -->
     <suppress checks="MissingJavadocMethod" files="src[\\/]main[\\/]java[\\/]org[\\/]spongepowered[\\/]configurate[\\/]examples[\\/].*"/>
+
+    <!-- Ignore generated files -->
+    <suppress checks=".*" files="build[\\/]generated(-src)?.*" />
 </suppressions>

format/json5/build.gradle.kts

@@ -0,0 +1,17 @@
+import org.spongepowered.configurate.build.core
+
+plugins {
+    id("org.spongepowered.configurate-component")
+    antlr
+}
+
+configurations.compile {
+    exclude("org.antlr", "antlr4")
+}
+
+dependencies {
+    antlr("org.antlr:antlr4:4.8-1")
+    implementation("org.antlr:antlr4-runtime:4.8-1")
+
+    api(core())
+}

format/json5/src/main/antlr/org/spongepowered/configurate/json5/Json5.g4

@@ -0,0 +1,128 @@
+grammar Json5;
+/**
+ * A grammar for the JSON5 document format.
+ *
+ * Based on the example grammar for JSON from The Definitive ANTLR 4 Reference ch6,
+ * and the JSON5 and ECMAScript 5.1 specifications.
+ */
+
+@header {
+package org.spongepowered.configurate.json5;
+}
+
+// Value types //
+
+document: object EOF;
+
+value: object#Compound
+    | array#Compound
+    | Json5NumericLiteral#Literal
+    | Json5String#Literal
+    | BooleanLiteral#Literal
+    | NullLiteral#Literal
+    ;
+
+object: '{' member (',' member)* ','? '}'
+    | '{' '}'
+    ;
+member : memberName ':' value;
+memberName: IdentifierName
+          | Json5String
+          ;
+
+array: '[' value (',' value)* ','? ']'
+    | '[' ']'
+    ;
+
+NullLiteral: 'null';
+BooleanLiteral: 'true'
+                | 'false';
+
+// ECMA Identifiers and Keywords //
+
+IdentifierName: IdentifierStart IdentifierPart*;
+
+Keyword: 'break' | 'do' | 'instanceof' | 'typeof'
+        | 'case' | 'else' | 'new' | 'var'
+        | 'catch' | 'finally' | 'return' | 'void'
+        | 'continue' | 'for' | 'switch' | 'while'
+        | 'debugger' | 'function' | 'this' | 'with'
+        | 'default' | 'if' | 'throw'
+        | 'delete' | 'in' | 'try'
+        ;
+
+FutureReservedWord: 'class' | 'enum' | 'extends' | 'super'
+                     | 'const' | 'export' | 'import'
+                     ;
+
+
+fragment IdentifierStart: UnicodeLetter | '$' | '_' | ('\\' UnicodeEscapeSequence);
+fragment IdentifierPart: IdentifierStart
+    | UnicodeCombiningMark
+    | UnicodeDigit
+    | UnicodeConnectorPunctuation
+    ;
+
+fragment UnicodeLetter: [\p{L}\p{Nl}]; // Unicode Letter or letterlike numeric character
+fragment UnicodeCombiningMark: [\p{Mn}\p{Mc}]; // Non-spacing mark or Combining spacing mark
+fragment UnicodeDigit: [\p{Nd}]; // Decimal number
+fragment UnicodeConnectorPunctuation: [\p{Pc}];
+
+
+// Strings //
+
+WS: [ \t\n\r\u000B\u000C\u2028\u2029\ufeff]+ -> skip;
+
+Json5String: '"' Json5DoubleStringCharacter* '"'
+            | '\'' Json5SingleStringCharacter* '\'';
+
+fragment Json5DoubleStringCharacter: ~('\\' | '"' | '\r' | '\n')
+                            | '\\' EscapeSequence
+                            | LineContinuation
+                            | '\u2028'
+                            | '\u2029';
+
+fragment Json5SingleStringCharacter: ~('\\' | '\'' | '\r' | '\n')
+                            | '\\' EscapeSequence
+                            | LineContinuation
+                            | '\u2028'
+                            | '\u2029';
+
+fragment EscapeSequence: '0' DecimalDigit
+                        | HexEscapeSequence
+                        | UnicodeEscapeSequence
+                        | ~[\r\n];
+
+fragment LineContinuation: '\\' NL;
+
+
+fragment HexEscapeSequence: 'x' HexDigit HexDigit;
+fragment UnicodeEscapeSequence: 'u' HexDigit HexDigit HexDigit HexDigit;
+
+// Numbers //
+
+Json5NumericLiteral: [+-]? (NumericLiteral
+                | 'Inifinity'
+                | 'NaN');
+
+fragment NumericLiteral: DecimalLiteral
+                | HexIntegerLiteral;
+
+DecimalLiteral:  DecimalIntegerLiteral '.' DecimalDigit* ExponentPart?
+                | '.' DecimalDigit+ ExponentPart?
+                | DecimalIntegerLiteral ExponentPart?;
+
+HexIntegerLiteral: '0x' HexDigit+;
+fragment DecimalIntegerLiteral: '0'
+                                | NonZeroDigit DecimalDigit*;
+fragment HexDigit: [0-9a-fA-F];
+fragment DecimalDigit: '0' | NonZeroDigit;
+fragment NonZeroDigit: [1-9];
+fragment ExponentPart: [eE] [+-]? DecimalDigit+;
+
+// Comments and newlines //
+
+fragment NL : '\r'? '\n';
+
+LINE_COMMENT: '//' .*? NL -> channel(HIDDEN);
+BLOCK_COMMENT: '/*' .*?  '*/' -> channel(HIDDEN);

format/json5/src/main/java/org/spongepowered/configurate/json5/Helpers.java

@@ -0,0 +1,34 @@
+/*
+ * Configurate
+ * Copyright (C) zml and Configurate contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.spongepowered.configurate.json5;
+
+/**
+ * Helpers for interacting with parsed values.
+ */
+final class Helpers {
+
+    private Helpers() {}
+
+    public static String unescape(final String input) {
+        return input; // TODO: implement
+    }
+
+    public static String unquote(final String input) {
+        return input.substring(1, input.length() - 1);
+    }
+
+}

format/json5/src/main/java/org/spongepowered/configurate/json5/Json5ConfigurationLoader.java

@@ -0,0 +1,120 @@
+/*
+ * Configurate
+ * Copyright (C) zml and Configurate contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.spongepowered.configurate.json5;
+
+import org.antlr.v4.runtime.BailErrorStrategy;
+import org.antlr.v4.runtime.CharStream;
+import org.antlr.v4.runtime.CharStreams;
+import org.antlr.v4.runtime.CommonTokenStream;
+import org.antlr.v4.runtime.ConsoleErrorListener;
+import org.antlr.v4.runtime.DefaultErrorStrategy;
+import org.antlr.v4.runtime.Token;
+import org.antlr.v4.runtime.atn.PredictionMode;
+import org.antlr.v4.runtime.misc.ParseCancellationException;
+import org.antlr.v4.runtime.tree.ParseTreeWalker;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.spongepowered.configurate.CommentedConfigurationNode;
+import org.spongepowered.configurate.ConfigurationNode;
+import org.spongepowered.configurate.ConfigurationOptions;
+import org.spongepowered.configurate.RepresentationHint;
+import org.spongepowered.configurate.loader.AbstractConfigurationLoader;
+import org.spongepowered.configurate.loader.CommentHandler;
+import org.spongepowered.configurate.loader.CommentHandlers;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.Writer;
+
+// TODO: Package-private generated files -- we may have to provide our own templates (sigh)
+// TODO: see https://github.com/antlr/antlr4/blob/master/tool/resources/org/antlr/v4/tool/templates/codegen/Java/Java.stg
+
+/**
+ * A loader for the <a href="https://json5.org">JSON5</a> language.
+ *
+ * <p>We use our own implementation, and aim to be fully complaint with the
+ * spec. Within those bounds, any features will be considered.</p>
+ */
+public final class Json5ConfigurationLoader extends AbstractConfigurationLoader<CommentedConfigurationNode> {
+
+    public static final RepresentationHint<NumberLayout> NUMBER_FORMAT = RepresentationHint.of("number_format", NumberLayout.class,
+            NumberLayout.DECIMAL);
+
+    public static Json5ConfigurationLoader.Builder builder() {
+        return new Builder();
+    }
+
+    Json5ConfigurationLoader(final @NonNull Builder builder) {
+        super(builder, new CommentHandler[]{CommentHandlers.SLASH_BLOCK, CommentHandlers.DOUBLE_SLASH});
+    }
+
+    @Override
+    protected void loadInternal(final CommentedConfigurationNode node, final BufferedReader reader) throws IOException {
+        final CharStream stream = CharStreams.fromReader(reader);
+        final Json5Lexer lexer = new Json5Lexer(stream);
+        final CommonTokenStream tokens = new CommonTokenStream(lexer);
+        final Json5Parser parser = new Json5Parser(tokens);
+        final ToNodeListener listener = new ToNodeListener(tokens, node);
+
+        // ANTLR 4 Reference 13.7, improving speed
+        // TODO: Use actions instead to avoid generating parse tree.
+        parser.getInterpreter().setPredictionMode(PredictionMode.SLL);
+        parser.removeErrorListeners();
+        parser.setErrorHandler(new BailErrorStrategy());
+        try {
+            ParseTreeWalker.DEFAULT.walk(listener, parser.document());
+            // success with the simpler method
+        } catch (final ParseCancellationException ex) {
+            // Reset node
+            node.setValue(null);
+            node.setComment(null);
+            // Reset state
+            tokens.seek(0);
+            parser.reset();
+
+            parser.addErrorListener(ConsoleErrorListener.INSTANCE); // TODO: Capture + throw all errors
+            parser.setErrorHandler(new DefaultErrorStrategy());
+
+            // with full prediction
+            parser.getInterpreter().setPredictionMode(PredictionMode.LL);
+            ParseTreeWalker.DEFAULT.walk(listener, parser.document());
+        }
+        for (Token token : tokens.getTokens()) {
+            System.out.println(token);
+        }
+    }
+
+    @Override
+    protected void saveInternal(final ConfigurationNode node, final Writer writer) throws IOException {
+        // TODO: writing
+    }
+
+    @Override
+    public CommentedConfigurationNode createNode(final ConfigurationOptions options) {
+        return CommentedConfigurationNode.root(options);
+    }
+
+    public static final class Builder extends AbstractConfigurationLoader.Builder<Builder> {
+
+        // TODO: provide options to customize output
+
+        @Override
+        public @NonNull Json5ConfigurationLoader build() {
+            return new Json5ConfigurationLoader(this);
+        }
+    }
+
+}

format/json5/src/main/java/org/spongepowered/configurate/json5/NumberLayout.java

@@ -0,0 +1,34 @@
+/*
+ * Configurate
+ * Copyright (C) zml and Configurate contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.spongepowered.configurate.json5;
+
+/**
+ * A method of presenting numbers.
+ */
+public enum NumberLayout {
+
+    /**
+     * Base-10 number representation.
+     */
+    DECIMAL,
+
+    /**
+     * Base-16 number representation.
+     */
+    HEX;
+
+}

format/json5/src/main/java/org/spongepowered/configurate/json5/QuotingStyle.java

@@ -0,0 +1,28 @@
+/*
+ * Configurate
+ * Copyright (C) zml and Configurate contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.spongepowered.configurate.json5;
+
+/**
+ * The preferred style for quoted strings.
+ */
+public enum QuotingStyle {
+
+    PREFER_SINGLE,
+    PREFER_DOUBLE,
+    PREFER_UNQUOTED;
+
+}