Switch Expressions (#186)

* Switch Expressions for Java 17+

Co-authored-by: Asaf Ben Natan <[email protected]>

docs/SYNTAX.md

@@ -243,6 +243,38 @@ both ```i am in the "a" block``` and ```i am in the "b" block"``` would be outpu
         }
     }
 
+### Enhanced Switch - case - default blocks (@switch) JDK17+
+
+Enhanced Java switch - case - default control flow. The left curly character ```{``` indicates
+the start of a block and the right curly character ```}``` marks the end.
+
+Switch block with case and default example.
+
+    @switch (s) {
+        case ("a") -> { 
+            i am in the "a" block
+        }
+        case ("b") -> {
+            i am in the "b" block
+        }
+        default -> {
+            i am in the "default" block
+        }
+    }
+
+Without a default block.
+
+    @switch (v) {
+        case (1) -> { 
+            i am in the "a" block
+        }
+        case (2) -> {
+            i am in the "b" block
+        }
+    }
+
+The Difference from normal Switch block is that @break is not required and each case is separate from the other.
+
 ### With blocks (set one or more variables) (@with)
 
 As of v0.12.0 a `@with` block sets a variable to a value within a scoped block. Once the block

pom.xml

@@ -174,5 +174,27 @@
 
         </dependencies>
     </dependencyManagement>
+    <!-- things to do if running on JDK 17 -->
+    <profiles>
+        <profile>
+            <id>java17-settings</id>
+            <activation>
+                <jdk>[17,)</jdk>
+            </activation>
+            <properties>
+                <javadoc.opts>-Xdoclint:none</javadoc.opts>
+            </properties>
+            <modules>
+                <module>rocker-runtime</module>
+                <module>rocker-compiler</module>
+                <module>rocker-maven-plugin</module>
+                <module>rocker-gradle-plugin</module>
+                <module>rocker-test-template</module>
+                <module>rocker-test-template17</module>
+                <module>rocker-test-reload</module>
+                <module>rocker-bom</module>
+            </modules>
+        </profile>
+    </profiles>
 
 </project>

rocker-compiler/src/main/antlr4/com/fizzed/rocker/antlr4/RockerLexer.g4

@@ -16,10 +16,19 @@ CASE
     :   Ws? 'case' Ws? Parentheses Ws? '{'
     ;
 
+//switch block should not allow WS as this will generate statments within switch block which are not case or default
+CASE_EXPRESSION
+    :   Ws? 'case' Ws? Parentheses Ws? '->' Ws? '{'
+    ;
+
 //switch block should not allow WS as this will generate statments within switch block which are not case or default
 DEFAULT
     :   Ws? 'default' Ws? '{' Ws?;
 
+//switch block should not allow WS as this will generate statments within switch block which are not case or default
+DEFAULT_EXPRESSION
+    :   Ws? 'default' Ws? '->' Ws? '{' Ws?;
+
 
 LCURLY
     :   '{'

rocker-compiler/src/main/antlr4/com/fizzed/rocker/antlr4/RockerParser.g4

@@ -59,7 +59,7 @@ templateContent
     ;
 
 block
-    :   (ifBlock | forBlock | withBlock|switchBlock)
+    :   (ifBlock | forBlock | withBlock | switchBlock | switchExpressionBlock)
     ;
 
 ifBlock
@@ -127,7 +127,7 @@ evalExpression
     ;
 
 switchBlock
-    :   AT MV_SWITCH  (switchCase|switchDefault|plain|comment)*  RCURLY
+    :   AT MV_SWITCH  ( switchCase | switchDefault | plain | comment)*  RCURLY
     ;
 
 switchCase
@@ -138,4 +138,15 @@ switchDefault
     :   DEFAULT templateContent*  RCURLY
     ;
 
+switchExpressionBlock
+    :   AT MV_SWITCH  ( switchExpressionCase | switchExpressionDefault | plain | comment)*  RCURLY
+    ;
+
+switchExpressionCase
+    :   CASE_EXPRESSION templateContent*  RCURLY
+    ;
+
+switchExpressionDefault
+    :   DEFAULT_EXPRESSION templateContent*  RCURLY
+    ;
 

rocker-compiler/src/main/java/com/fizzed/rocker/compiler/JavaGenerator.java

@@ -1053,6 +1053,63 @@ else if (unit instanceof SwitchDefaultBlockEnd) {
                         .append(blockEnd.pop())
                         .append(" // default end ").append(sourceRef(unit)).append(CRLF);
             }
+
+            else if(unit instanceof SwitchExpressionBlock){
+
+                SwitchExpressionBlock block = (SwitchExpressionBlock) unit;
+
+                tab(w, depth+indent)
+                        .append("switch ")
+                        .append(block.getExpression())
+                        .append(" {").append(CRLF);
+
+                blockEnd.push("}");
+
+                depth++;
+            } else if (unit instanceof SwitchExpressionBlockEnd) {
+                depth--;
+
+                tab(w, depth+indent)
+                        .append(blockEnd.pop())
+                        .append(" // switch end ").append(sourceRef(unit)).append(CRLF);
+
+
+            } else if (unit instanceof SwitchCaseExpressionBlock) {
+
+                SwitchCaseExpressionBlock block = (SwitchCaseExpressionBlock) unit;
+
+                tab(w, depth+indent)
+                        .append("case ")
+                        .append(block.getExpression())
+                        .append(" -> ")
+                        .append(" {").append(CRLF);
+
+                blockEnd.push("}");
+
+                depth++;
+            } else if (unit instanceof SwitchCaseExpressionBlockEnd) {
+                depth--;
+
+                tab(w, depth+indent)
+                        .append(blockEnd.pop())
+                        .append(" // case end ").append(sourceRef(unit)).append(CRLF);
+            }else if (unit instanceof SwitchDefaultExpressionBlock) {
+
+                tab(w, depth+indent)
+                        .append("default ")
+                        .append("-> ")
+                        .append(" {").append(CRLF);
+
+                blockEnd.push("}");
+                depth++;
+            }
+            else if (unit instanceof SwitchDefaultExpressionBlockEnd) {
+                depth--;
+
+                tab(w, depth+indent)
+                        .append(blockEnd.pop())
+                        .append(" // default end ").append(sourceRef(unit)).append(CRLF);
+            }
             //log.info(" src (@ {}): [{}]", unit.getSourceRef(), unit.getSourceRef().getConsoleFriendlyText());
         }
 
@@ -1149,5 +1206,7 @@ private TemplateModel postProcess(TemplateModel templateModel) throws PostProces
 
         return templateModel;
     }
+
+
 
 }

rocker-compiler/src/main/java/com/fizzed/rocker/compiler/TemplateParser.java

@@ -950,6 +950,55 @@ public void exitSwitchBlock(RockerParser.SwitchBlockContext ctx) {
             verifySwitchBlock();
         }
 
+        @Override
+        public void enterSwitchExpressionBlock(RockerParser.SwitchExpressionBlockContext ctx) {
+
+            SourceRef sourceRef = createSourceRef(ctx);
+            final String text = ctx.MV_SWITCH().getText();
+            final int idxFirst = text.indexOf('(');
+            final int idxLast = text.lastIndexOf(')');
+            final String expression = text.substring(idxFirst, idxLast + 1);
+            model.getUnits().add(new SwitchExpressionBlock(sourceRef, expression));
+        }
+
+        @Override
+        public void exitSwitchExpressionBlock(RockerParser.SwitchExpressionBlockContext ctx) {
+            SourceRef sourceRef = createSourceRef(ctx);
+            model.getUnits().add(new SwitchExpressionBlockEnd(sourceRef));
+            verifySwitchExpressionBlock();
+        }
+
+        @Override
+        public void enterSwitchExpressionCase(RockerParser.SwitchExpressionCaseContext ctx) {
+
+            SourceRef sourceRef = createSourceRef(ctx);
+            final String text = ctx.CASE_EXPRESSION().getText();
+            final int idxFirst = text.indexOf('(');
+            final int idxLast = text.lastIndexOf(')');
+            final String expression = text.substring(idxFirst+1, idxLast );
+            model.getUnits().add(new SwitchCaseExpressionBlock(sourceRef, expression));
+
+        }
+
+        @Override
+        public void exitSwitchExpressionCase(RockerParser.SwitchExpressionCaseContext ctx) {
+             SourceRef sourceRef = createSourceRef(ctx);
+            model.getUnits().add(new SwitchCaseExpressionBlockEnd(sourceRef));
+        }
+
+        @Override
+        public void enterSwitchExpressionDefault(RockerParser.SwitchExpressionDefaultContext ctx) {
+            SourceRef sourceRef = createSourceRef(ctx);
+            model.getUnits().add(new SwitchDefaultExpressionBlock(sourceRef));
+        }
+
+        @Override
+        public void exitSwitchExpressionDefault(RockerParser.SwitchExpressionDefaultContext ctx) {
+            SourceRef sourceRef = createSourceRef(ctx);
+            model.getUnits().add(new SwitchDefaultExpressionBlockEnd(sourceRef));
+
+        }
+
         private void verifySwitchBlock() {
 
             List<TemplateUnit> units = this.model.getUnits();
@@ -971,6 +1020,27 @@ private void verifySwitchBlock() {
             }
             units.removeAll(toRemove);
         }
+        private void verifySwitchExpressionBlock() {
+
+            List<TemplateUnit> units = this.model.getUnits();
+            List<TemplateUnit> toRemove=new ArrayList<>();
+            for (int i = 0, unitsSize = units.size(); i < unitsSize; i++) {
+                TemplateUnit unit = units.get(i);
+                if (unit instanceof PlainText) {
+                    PlainText plain = (PlainText) unit;
+                    if (inSwitchExpressionButNotCaseOrDefault(i)) {
+                        if (plain.isWhitespace()) {
+                            toRemove.add(unit);
+                        } else {
+                            // no plain allowed
+                            SourcePosition pos = plain.findSourcePositionOfNonWhitespace();
+                            throw new ParserRuntimeException(pos.getLineNumber(), pos.getPosInLine(), "plain text not allowed before end of switch block");
+                        }
+                    }
+                }
+            }
+            units.removeAll(toRemove);
+        }
 
         private boolean inSwitchButNotCaseOrDefault(int i) {
             for (int j = i; j >= 0; j--) {
@@ -984,6 +1054,18 @@ private boolean inSwitchButNotCaseOrDefault(int i) {
             }
             return false;
         }
+        private boolean inSwitchExpressionButNotCaseOrDefault(int i) {
+            for (int j = i; j >= 0; j--) {
+                TemplateUnit templateUnit = model.getUnits().get(j);
+                if (templateUnit instanceof SwitchCaseExpressionBlockEnd || templateUnit instanceof SwitchDefaultExpressionBlockEnd || templateUnit instanceof SwitchExpressionBlock) {
+                    return true;
+                }
+                if (templateUnit instanceof SwitchCaseExpressionBlock || templateUnit instanceof SwitchDefaultExpressionBlock || templateUnit instanceof SwitchExpressionBlockEnd) {
+                    return false;
+                }
+            }
+            return false;
+        }
 
         @Override
         public void enterSwitchCase(RockerParser.SwitchCaseContext ctx) {

rocker-compiler/src/main/java/com/fizzed/rocker/model/SwitchCaseExpressionBlock.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2017 Fizzed Inc.
+ *
+ * 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 com.fizzed.rocker.model;
+
+/**
+ * Represents else-if part of an if block.
+ */
+public class SwitchCaseExpressionBlock extends BlockBegin {
+
+  public SwitchCaseExpressionBlock(final SourceRef sourceRef, final String expression) {
+    super(sourceRef, expression);
+  }
+  @Override
+  public boolean supportsSourceJournaling() {
+    return false;
+  }
+}

rocker-compiler/src/main/java/com/fizzed/rocker/model/SwitchCaseExpressionBlockEnd.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2015 Fizzed Inc.
+ *
+ * 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 com.fizzed.rocker.model;
+
+/**
+ *
+ * @author joelauer
+ */
+public class SwitchCaseExpressionBlockEnd extends BlockEnd {
+
+    public SwitchCaseExpressionBlockEnd(SourceRef sourceRef) {
+        super(sourceRef);
+    }
+    @Override
+    public boolean supportsSourceJournaling() {
+        return false;
+    }
+}

rocker-compiler/src/main/java/com/fizzed/rocker/model/SwitchDefaultExpressionBlock.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2017 Fizzed Inc.
+ *
+ * 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 com.fizzed.rocker.model;
+
+/**
+ * Represents else-if part of an if block.
+ */
+public class SwitchDefaultExpressionBlock extends BlockBegin {
+
+  public SwitchDefaultExpressionBlock(final SourceRef sourceRef) {
+    super(sourceRef,null );
+  }
+  @Override
+  public boolean supportsSourceJournaling() {
+    return false;
+  }
+}