[DO-NOT-MERGE][incubator-kie-drools-6220] Slim down DRL syntax with New Antlr4 Parser

.github/workflows/pr-downstream.yml

@@ -33,6 +33,7 @@ on:
 
 jobs:
   kogito-downstream-build:
+    if: false
     concurrency:
       group: pr-${{ matrix.job_name }}_${{ matrix.os }}_${{ matrix.java-version }}_${{ matrix.maven-version }}_${{ github.head_ref }}
       cancel-in-progress: true

.github/workflows/pr-drools.yml

@@ -61,7 +61,7 @@ jobs:
       - name: Build Chain
         uses: apache/incubator-kie-kogito-pipelines/.ci/actions/build-chain@main
         env:
-          BUILD_MVN_OPTS_CURRENT: '-Dfull -Dreproducible'
+          BUILD_MVN_OPTS_CURRENT: '-Dfull -Dreproducible -DenableNewParser'
           MAVEN_OPTS: "-Dfile.encoding=UTF-8"
         with:
           definition-file: https://raw.githubusercontent.com/${GROUP:apache}/incubator-kie-kogito-pipelines/${BRANCH:main}/.ci/pull-request-config.yaml

.gitignore

@@ -29,6 +29,7 @@ nbproject
 *.ipr
 *.iws
 *.iml
+build.log
 
 # generated files
 dependency-reduced-pom.xml

drools-docs/src/modules/ROOT/pages/language-reference/_language-level.adoc

@@ -0,0 +1,146 @@
+////
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you 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.
+////
+
+[id='language-level_drl-rules']
+
+= Language Level
+
+Language Level is a feature that allows you to specify the version of the DRL (Drools Rule Language) syntax you want to use.
+
+Supported language levels are:
+
+* DRL6 (default)
+* DRL10
+
+Some old language levels are deprecated and will be removed in the future:
+
+* DRL5
+* DRL6_STRICT
+
+DRL6 is compatible with the previous Drools versions, while DRL10 introduces some changes to reduce ambiguity.
+
+Language Level can be specified by kmodule.xml or system property. Note that the configuration should be effective when rules are built.
+
+.kmodule.xml example
+[source,xml]
+----
+<kmodule xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xmlns="http://www.drools.org/xsd/kmodule">
+  <configuration>
+    <property key="drools.lang.level" value="DRL10"/>
+  </configuration>
+</kmodule>
+----
+
+.System property example
+[source,java]
+----
+    System.setProperty("drools.lang.level", "DRL10");
+----
+
+== DRL10
+
+DRL10 has been added, which is handled by the new parser based on ANTLR4. DRL10 introduces the following changes mainly to reduce ambiguity:
+
+* Require a prefix `##` to custom operators
+.DRL6
+[source]
+----
+   Person(addresses supersetOf $alice.addresses)
+----
+
+.DRL10
+[source]
+----
+   Person(addresses ##supersetOf $alice.addresses)
+----
+
+The custom operator's implementation Java code wouldn't need to be changed.
+
+* Drop half constraint syntax
+
+.DRL6
+[source]
+----
+   Person(age > 10 && < 20)
+----
+
+.DRL10 (also valid in DRL6)
+[source]
+----
+   Person(age > 10 && age < 20)
+----
+
+* Drop double ampersand as infix and
+
+.DRL6
+[source]
+----
+   ( Person(age == 10)
+      &&
+     Person(age == 20) )
+----
+
+.DRL10 (also valid in DRL6)
+[source]
+----
+   ( Person(age == 10)
+      and
+     Person(age == 20) )
+----
+
+`&&` in a constraint will remain supported. For example, `Person(age == 10 && age == 20)` is valid in DRL6 and DRL10.
+
+* Drop double pipe as infix or
+
+.DRL6
+[source]
+----
+   ( Person(age == 10)
+      ||
+     Person(age == 20) )
+----
+
+.DRL10 (also valid in DRL6)
+[source]
+----
+   ( Person(age == 10)
+      or
+     Person(age == 20) )
+----
+
+`||` in a constraint will remain supported. For example, `Person(age == 10 || age == 20)` is valid in DRL6 and DRL10.
+
+* Drop annotation inside LHS pattern
+
+.DRL6
+[source]
+----
+       ( Double()
+          or @Annot1 String()
+          or @Annot2 Integer() )
+----
+
+There is no equivalent expression in DRL10.
+
+Annotation in other places will remain supported. For example, `Person(name == "Mario") @watch(*)` is valid in DRL6 and DRL10.
+
+Those syntaxes are deprecated and will be removed in the future. Warnings are logged when the deprecated syntax is used in DRL6.
+
+Warnings are logged when the deprecated syntax is used in DRL6. The warning logs can be suppressed by the log level of `org.drools.drl.parser.lang.ParserHelper`.

drools-docs/src/modules/ROOT/pages/language-reference/index.adoc

@@ -29,3 +29,5 @@ include::_drl-rules.adoc[leveloffset=+1]
 include::_performance-tuning-drl-ref.adoc[leveloffset=+2]
 
 include::_XLSDecisionTable-section.adoc[leveloffset=+1]
+
+include::_language-level.adoc[leveloffset=+1]

drools-docs/src/modules/ROOT/pages/release-notes/_release-notes-10.1.adoc

@@ -0,0 +1,35 @@
+////
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you 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.
+////
+
+== 10.1.0 release notes
+
+=== Language Level DRL10
+New language level DRL10 has been added. DRL10 is handled by the new parser based on ANTLR4. The default language level is still DRL6.
+
+DRL10 introduces the following changes mainly to reduce ambiguity:
+
+* Require a prefix '##' to custom operators
+* Drop half constraint syntax
+* Drop double ampersand as infix and
+* Drop double pipe as infix or
+* Drop annotation inside LHS pattern
+
+Those syntaxes are deprecated and will be removed in the future. Warnings are logged when the deprecated syntax is used in DRL6.
+
+You can refer xref:language-reference/index.adoc#language-level_drl-rules[Language Level] for details.

drools-docs/src/modules/ROOT/pages/release-notes/index.adoc

@@ -30,6 +30,8 @@ This chapter contains the release notes for the {PRODUCT} 10-series.
 
 For the release notes of the _previous releases_, you can refer to the {PRODUCT} documentation of link:https://docs.drools.org/8.44.0.Final/drools-docs/drools/release-notes/index.html[version 8].
 
+include::_release-notes-10.1.adoc[leveloffset=0]
+
 include::_release-notes-10.0.adoc[leveloffset=0]
 
 == Drools 10-series release notes

drools-drl/drools-drl-ast/src/main/java/org/drools/drl/ast/descr/OperatorDescr.java

@@ -26,6 +26,9 @@
 public class OperatorDescr extends BaseDescr {
     private static final long serialVersionUID = 520l;
 
+    // prefix for custom operators which are not built-in
+    public static final String CUSTOM_OPERATOR_PREFIX = "##";
+
     private String            operator;
     private boolean           negated;
     private List<String>      parameters;
@@ -55,7 +58,15 @@ public String getOperator() {
     }
 
     public void setOperator( String operator ) {
-        this.operator = operator != null ? operator.trim() : null;
+        this.operator = operator != null ? trimOperator(operator) : null;
+    }
+
+    private String trimOperator(String operator) {
+        operator = operator.trim();
+        if (operator.startsWith(CUSTOM_OPERATOR_PREFIX)) {
+            operator = operator.substring(CUSTOM_OPERATOR_PREFIX.length());
+        }
+        return operator;
     }
 
     public boolean isNegated() {

drools-drl/drools-drl-ast/src/main/java/org/drools/drl/ast/dsl/DescrBuilder.java

@@ -88,4 +88,14 @@ public DescrBuilder<P, T> endLocation( int line,
      * @return
      */
     public P end();
+
+    /**
+     * Returns the parent container of this descr builder.
+     * Example: ruleDescrBuilder.getParent() will return the
+     * PackageDescrBuilder as that is its parent container
+     * without ending the current construction.
+     *
+     * @return
+     */
+    public P getParent();
 }

drools-drl/drools-drl-ast/src/main/java/org/drools/drl/ast/dsl/impl/BaseDescrBuilderImpl.java

@@ -72,4 +72,8 @@ public P end() {
         return parent;
     }
 
+    @Override
+    public P getParent() {
+        return parent;
+    }
 }

drools-drl/drools-drl-parser-tests/src/test/java/org/drools/drl/parser/antlr4/DRLParserTest.java → drools-drl/drools-drl-parser-tests/src/test/java/org/drools/drl/parser/antlr4/DRL10ParserTest.java

@@ -31,14 +31,14 @@
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.drools.drl.parser.antlr4.DRLParserHelper.computeTokenIndex;
-import static org.drools.drl.parser.antlr4.DRLParserHelper.createDrlParser;
-import static org.drools.drl.parser.antlr4.DRLParserHelper.parse;
+import static org.drools.drl.parser.antlr4.DRL10ParserHelper.computeTokenIndex;
+import static org.drools.drl.parser.antlr4.DRL10ParserHelper.createDrlParser;
+import static org.drools.drl.parser.antlr4.DRL10ParserHelper.parse;
 
 /**
  * This test class is specific to new antlr4 parser.
  */
-class DRLParserTest {
+class DRL10ParserTest {
 
     private static final String drl =
             "package org.test;\n" +
@@ -94,7 +94,7 @@ void parse_basicRule() {
 
     @Test
     void computeTokenIndex_basicRule() {
-        DRLParser parser = createDrlParser(drl);
+        DRL10Parser parser = createDrlParser(drl);
         parser.compilationUnit();
 
         assertThat((int) computeTokenIndex(parser, 1, 0)).isEqualTo(0);

drools-drl/drools-drl-parser-tests/src/test/java/org/drools/drl/parser/antlr4/DRLExprParserTest.java

@@ -27,7 +27,6 @@
 import org.drools.drl.ast.descr.ConstraintConnectiveDescr;
 import org.drools.drl.ast.descr.RelationalExprDescr;
 import org.drools.drl.parser.DrlExprParser;
-import org.drools.drl.parser.DrlExprParserFactory;
 import org.drools.drl.parser.DrlParser;
 import org.drools.drl.parser.DroolsParserException;
 import org.drools.drl.parser.impl.Operator;
@@ -38,7 +37,6 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.EnumSource;
 import org.junit.jupiter.params.provider.ValueSource;
-import org.kie.internal.builder.conf.LanguageLevelOption;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assumptions.assumeFalse;
@@ -52,7 +50,7 @@ class DRLExprParserTest {
 
     @BeforeEach
     void setUp() {
-        this.parser = DrlExprParserFactory.getDrlExprParser(LanguageLevelOption.DRL6);
+        this.parser = ParserTestUtils.getExprParser();
     }
 
     @AfterEach
@@ -175,7 +173,7 @@ void bindingConstraint() {
 
     @Test
     void bindingWithRestrictions() {
-        String source = "$x : property > value && < 20";
+        String source = "$x : property > value && property < 20";
         ConstraintConnectiveDescr result = parser.parse( source );
         assertThat(parser.hasErrors()).as(parser.getErrors().toString()).isFalse();
 
@@ -458,7 +456,7 @@ void noViableAlt() {
             assertThat(exception.getColumn()).isEqualTo(2);
             assertThat(exception.getOffset()).isEqualTo(2);
             assertThat(exception.getMessage())
-                    .isEqualToIgnoringCase("[ERR 101] Line 1:2 no viable alternative at input 'a'");
+                    .isEqualToIgnoringCase("[ERR 101] Line 1:2 no viable alternative at input '~a'");
         } else {
             assertThat(parser.hasErrors()).isFalse();
         }
@@ -578,4 +576,48 @@ void newBigDecimal() {
         assertThat(bind.getVariable()).isEqualTo("$bd");
         assertThat(bind.getExpression()).isEqualTo("new BigDecimal(30)");
     }
+
+    @Test
+    void halfConstraintAnd() {
+        String source = "age > 10 && < 20";
+        parser.parse(source);
+
+        if (DrlParser.ANTLR4_PARSER_ENABLED) {
+            // half constraint is dropped in DRL10
+            assertThat(parser.hasErrors()).isTrue();
+        } else {
+            assertThat(parser.hasErrors()).as(parser.getErrors().toString()).isFalse();
+        }
+    }
+
+    @Test
+    void halfConstraintOr() {
+        String source = "name == \"John\" || == \"Paul\"";
+        parser.parse(source);
+
+        if (DrlParser.ANTLR4_PARSER_ENABLED) {
+            // half constraint is dropped in DRL10
+            assertThat(parser.hasErrors()).isTrue();
+        } else {
+            assertThat(parser.hasErrors()).as(parser.getErrors().toString()).isFalse();
+        }
+    }
+
+    @Test
+    void customOperator() {
+        Operator.addOperatorToRegistry("supersetOf", false);
+        // prefix '##' is required for custom operators in DRL10
+        String source = DrlParser.ANTLR4_PARSER_ENABLED ? "this ##supersetOf $list" : "this supersetOf $list";
+        ConstraintConnectiveDescr result = parser.parse(source);
+        assertThat(parser.hasErrors()).as(parser.getErrors().toString()).isFalse();
+
+        RelationalExprDescr rel = (RelationalExprDescr) result.getDescrs().get(0);
+        assertThat(rel.getOperator()).isEqualTo("supersetOf");
+
+        AtomicExprDescr left = (AtomicExprDescr) rel.getLeft();
+        assertThat(left.getExpression()).isEqualTo("this");
+
+        AtomicExprDescr right = (AtomicExprDescr) rel.getRight();
+        assertThat(right.getExpression()).isEqualTo("$list");
+    }
 }