Support choice expressions

14 files changed, 205 insertions, 65 deletions

diff --git a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ChoiceExpression.java b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ChoiceExpression.java
new file mode 100644
index 00000000000..5d92b726ce4
--- /dev/null
+++ b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ChoiceExpression.java
@@ -0,0 +1,87 @@
+package com.yahoo.vespa.indexinglanguage.expressions;
+
+import com.yahoo.document.DataType;
+import com.yahoo.document.datatypes.FieldValue;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * An expression which returns the value of the first of a list of subexpressions which
+ * returns a non-null value.
+ *
+ * Syntax: sub-expression1 || sub-expression2 || ...
+ *
+ * @author bratseth
+ */
+public class ChoiceExpression extends ExpressionList<Expression> {
+
+    public ChoiceExpression() {
+        this(List.of());
+    }
+
+    public ChoiceExpression(Expression... choices) {
+        this(Arrays.asList(choices));
+    }
+
+    public ChoiceExpression(Collection<? extends Expression> choices) {
+        super(choices, resolveInputType(choices));
+    }
+
+    @Override
+    protected void doExecute(ExecutionContext context) {
+        FieldValue input = context.getValue();
+        for (Expression expression : this) {
+            context.setValue(input).execute(expression);
+            if (context.getValue() != null)
+                break; // value found
+        }
+    }
+
+    @Override
+    protected void doVerify(VerificationContext context) {
+        DataType input = context.getValueType();
+        for (Expression exp : this)
+            context.setValueType(input).execute(exp);
+        context.setValueType(input);
+    }
+
+    private static DataType resolveInputType(Collection<? extends Expression> list) {
+        DataType previousInput = null;
+        DataType previousOutput = null;
+        for (Expression choice : list) {
+            DataType thisInput = choice.requiredInputType();
+            if (previousInput == null)
+                previousInput = thisInput;
+            else if (thisInput != null && !previousInput.isAssignableFrom(thisInput))
+                throw new VerificationException(ScriptExpression.class, "Choice expressions require conflicting input types, " +
+                                                                        previousInput.getName() + " vs " + thisInput.getName() + ".");
+
+            DataType thisOutput = choice.createdOutputType();
+            if (previousOutput == null)
+                previousOutput = thisOutput;
+            else if (thisOutput != null && !previousOutput.isAssignableFrom(thisOutput))
+                throw new VerificationException(ScriptExpression.class, "Choice expressions produce conflicting output types, " +
+                                                                        previousOutput.getName() + " vs " + thisOutput.getName() + ".");
+        }
+        return previousInput;
+    }
+
+    @Override
+    public DataType createdOutputType() {
+        return UnresolvedDataType.INSTANCE;
+    }
+
+    @Override
+    public String toString() {
+        return asList().stream().map(Object::toString).collect(Collectors.joining(" || "));
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        return super.equals(obj) && obj instanceof ChoiceExpression;
+    }
+
+}
diff --git a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/CompositeExpression.java b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/CompositeExpression.java
index 64043eddab8..27e5524f4ad 100644
--- a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/CompositeExpression.java
+++ b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/CompositeExpression.java
@@ -11,6 +11,7 @@ public abstract class CompositeExpression extends Expression {
     protected CompositeExpression(DataType inputType) {
         super(inputType);
     }
+
     protected static String toScriptBlock(Expression exp) {
         if (exp instanceof ScriptExpression) {
             return exp.toString();
diff --git a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ExecutionContext.java b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ExecutionContext.java
index 389259cc811..d463bee647e 100644
--- a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ExecutionContext.java
+++ b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ExecutionContext.java
@@ -31,9 +31,8 @@ public class ExecutionContext implements FieldTypeAdapter, FieldValueAdapter, Cl
     }
 
     public ExecutionContext execute(Expression exp) {
-        if (exp != null) {
+        if (exp != null)
             exp.execute(this);
-        }
         return this;
     }
 
@@ -65,9 +64,8 @@ public class ExecutionContext implements FieldTypeAdapter, FieldValueAdapter, Cl
 
     @Override
     public ExecutionContext setOutputValue(Expression exp, String fieldName, FieldValue fieldValue) {
-        if (adapter == null) {
+        if (adapter == null)
             throw new IllegalStateException("Can not set field '" + fieldName + "' because adapter is null.");
-        }
         adapter.setOutputValue(exp, fieldName, fieldValue);
         return this;
     }
diff --git a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/Expression.java b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/Expression.java
index cabf4f631c8..bf8201ee7ee 100644
--- a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/Expression.java
+++ b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/Expression.java
@@ -206,18 +206,13 @@ public abstract class Expression extends Selectable {
 
     protected static boolean equals(Object lhs, Object rhs) {
         if (lhs == null) {
-            if (rhs != null) {
-                return false;
-            }
+            return rhs == null;
         } else {
             if (rhs == null) {
                 return false;
             }
-            if (!lhs.equals(rhs)) {
-                return false;
-            }
+            return lhs.equals(rhs);
         }
-        return true;
     }
 
     // Convenience For testing
diff --git a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ExpressionList.java b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ExpressionList.java
index ff0a325b23f..e2ff1de7126 100644
--- a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ExpressionList.java
+++ b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ExpressionList.java
@@ -56,12 +56,8 @@ public abstract class ExpressionList<T extends Expression> extends CompositeExpr
     @Override
     @SuppressWarnings("rawtypes")
     public boolean equals(Object obj) {
-        if (!(obj instanceof ExpressionList rhs)) {
-            return false;
-        }
-        if (!expressions.equals(rhs.expressions)) {
-            return false;
-        }
+        if (!(obj instanceof ExpressionList rhs)) return false;
+        if (!expressions.equals(rhs.expressions)) return false;
         return true;
     }
 
diff --git a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/IfThenExpression.java b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/IfThenExpression.java
index 72cd65e43ed..8a29c8e8645 100644
--- a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/IfThenExpression.java
+++ b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/IfThenExpression.java
@@ -191,7 +191,7 @@ public final class IfThenExpression extends CompositeExpression {
         }
         if (!prev.equals(next)) {
             throw new VerificationException(IfThenExpression.class, "Operands require conflicting input types, " +
-                                                  prev.getName() + " vs " + next.getName() + ".");
+                                                                    prev.getName() + " vs " + next.getName() + ".");
         }
         return prev;
     }
diff --git a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/InputExpression.java b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/InputExpression.java
index de347904a21..30c824d410d 100644
--- a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/InputExpression.java
+++ b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/InputExpression.java
@@ -9,6 +9,7 @@ import com.yahoo.vespa.objects.ObjectPredicate;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * @author Simon Thoresen Hult
@@ -20,7 +21,7 @@ public final class InputExpression extends Expression {
 
     public InputExpression(String fieldName) {
         super(null);
-        this.fieldName = fieldName;
+        this.fieldName = Objects.requireNonNull(fieldName);
     }
 
     public String getFieldName() {
@@ -29,19 +30,17 @@ public final class InputExpression extends Expression {
 
     @Override
     protected void doExecute(ExecutionContext context) {
-        if (fieldPath != null) {
+        if (fieldPath != null)
             context.setValue(context.getInputValue(fieldPath));
-        } else {
+        else
             context.setValue(context.getInputValue(fieldName));
-        }
     }
 
     @Override
     protected void doVerify(VerificationContext context) {
         DataType val = context.getInputType(this, fieldName);
-        if (val == null) {
+        if (val == null)
             throw new VerificationException(this, "Field '" + fieldName + "' not found.");
-        }
         context.setValueType(val);
     }
 
@@ -92,8 +91,6 @@ public final class InputExpression extends Expression {
 
         private final List<String> inputFieldNames = new ArrayList<>(1);
 
-        public List<String> getInputFieldNames() { return inputFieldNames; }
-
         @Override
         public void execute(Object obj) {
             inputFieldNames.add(((InputExpression) obj).getFieldName());
@@ -104,6 +101,12 @@ public final class InputExpression extends Expression {
             return obj instanceof InputExpression;
         }
 
+        public static List<String> runOn(Expression expression) {
+            InputExpression.InputFieldNameExtractor inputFieldNameExtractor = new InputExpression.InputFieldNameExtractor();
+            expression.select(inputFieldNameExtractor, inputFieldNameExtractor);
+            return inputFieldNameExtractor.inputFieldNames;
+        }
+
     }
 
 }
diff --git a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ScriptExpression.java b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ScriptExpression.java
index d2f807b99ae..8287252b268 100644
--- a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ScriptExpression.java
+++ b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ScriptExpression.java
@@ -15,6 +15,7 @@ import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Iterator;
+import java.util.List;
 import java.util.Map;
 
 /**
@@ -37,11 +38,20 @@ public final class ScriptExpression extends ExpressionList<StatementExpression>
     @Override
     protected void doExecute(ExecutionContext context) {
         FieldValue input = context.getValue();
-        for (Expression expression : this)
-            context.setValue(input).execute(expression);
+        for (StatementExpression statement : this) {
+            if (statement.getInputFields().isEmpty() || containsAtLeastOneInputFrom(statement.getInputFields(), context))
+                context.setValue(input).execute(statement);
+        }
         context.setValue(input);
     }
 
+    private boolean containsAtLeastOneInputFrom(List<String> inputFields, ExecutionContext context) {
+        for (String inputField : inputFields)
+            if (context.getInputValue(inputField) != null)
+                return true;
+        return false;
+    }
+
     @Override
     protected void doVerify(VerificationContext context) {
         DataType input = context.getValueType();
@@ -59,7 +69,7 @@ public final class ScriptExpression extends ExpressionList<StatementExpression>
                 prev = next;
             } else if (next != null && !prev.isAssignableFrom(next)) {
                 throw new VerificationException(ScriptExpression.class, "Statements require conflicting input types, " +
-                                                      prev.getName() + " vs " + next.getName() + ".");
+                                                                        prev.getName() + " vs " + next.getName() + ".");
             }
         }
         return prev;
diff --git a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/StatementExpression.java b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/StatementExpression.java
index 1a43d2fb36c..8516ddb883d 100644
--- a/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/StatementExpression.java
+++ b/indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/StatementExpression.java
@@ -15,13 +15,17 @@ import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.stream.Collectors;
 
 /**
  * @author Simon Thoresen Hult
  */
 public final class StatementExpression extends ExpressionList<Expression> {
 
-    /** The name of the (last) output field tthis statement will write to, or null if none */
+    /** The names of the fields consumed by this. */
+    private final List<String> inputFields;
+
+    /** The name of the (last) output field this statement will write to, or null if none */
     private String outputField;
 
     public StatementExpression(Expression... lst) {
@@ -34,12 +38,17 @@ public final class StatementExpression extends ExpressionList<Expression> {
 
     private StatementExpression(Iterable<Expression> list, Object unused) {
         super(list, resolveInputType(list));
+        inputFields = List.copyOf(InputExpression.InputFieldNameExtractor.runOn(this));
     }
 
+    /** Returns the input fields which are (perhaps optionally) consumed by some expression in this statement. */
+    public List<String> getInputFields() { return inputFields; }
+
     @Override
     protected void doExecute(ExecutionContext context) {
-        for (Expression expression : this)
+        for (Expression expression : this) {
             context.execute(expression);
+        }
     }
 
     @Override
@@ -57,14 +66,10 @@ public final class StatementExpression extends ExpressionList<Expression> {
     private static DataType resolveInputType(Iterable<Expression> lst) {
         for (Expression exp : lst) {
             DataType type = exp.requiredInputType();
-            if (type != null) {
-                return type;
-            }
+            if (type != null) return type;
 
             type = exp.createdOutputType();
-            if (type != null) {
-                return null;
-            }
+            if (type != null) return null;
         }
         return null;
     }
@@ -73,23 +78,14 @@ public final class StatementExpression extends ExpressionList<Expression> {
     public DataType createdOutputType() {
         for (int i = size(); --i >= 0; ) {
             DataType type = get(i).createdOutputType();
-            if (type != null) {
-                return type;
-            }
+            if (type != null) return type;
         }
         return null;
     }
 
     @Override
     public String toString() {
-        StringBuilder ret = new StringBuilder();
-        for (Iterator<Expression> it = iterator(); it.hasNext();) {
-            ret.append(it.next());
-            if (it.hasNext()) {
-                ret.append(" | ");
-            }
-        }
-        return ret.toString();
+        return asList().stream().map(Expression::toString).collect(Collectors.joining(" | "));
     }
 
     @Override
diff --git a/indexinglanguage/src/main/javacc/IndexingParser.jj b/indexinglanguage/src/main/javacc/IndexingParser.jj
index 51bb9be1f8a..9f0b4733119 100644
--- a/indexinglanguage/src/main/javacc/IndexingParser.jj
+++ b/indexinglanguage/src/main/javacc/IndexingParser.jj
@@ -8,7 +8,6 @@ options {
     CACHE_TOKENS = false;
     DEBUG_PARSER = false;
     ERROR_REPORTING = true;
-    STATIC = false;
     USER_CHAR_STREAM = true;
 }
 
@@ -24,7 +23,7 @@ package com.yahoo.vespa.indexinglanguage.parser;
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.List;
-import java.util.LinkedList;
+import java.util.ArrayList;
 import java.util.Map;
 import java.util.LinkedHashMap;
 
@@ -137,6 +136,7 @@ TOKEN :
     <LE: "<="> |
     <GT: ">"> |
     <GE: ">="> |
+    <CHOICE: "||"> |
     <PIPE: "|"> |
     <LCURLY: "{"> |
     <RCURLY: "}"> |
@@ -229,7 +229,7 @@ Expression root() :
 ScriptExpression script() :
 {
     StatementExpression exp;
-    List<StatementExpression> lst = new LinkedList<StatementExpression>();
+    List<StatementExpression> lst = new ArrayList<StatementExpression>();
 }
 {
     (   <LCURLY> nl()   exp = statement() { lst.add(exp); } nl()
@@ -240,7 +240,7 @@ ScriptExpression script() :
 StatementExpression statement() :
 {
     Expression exp;
-    List<Expression> lst = new LinkedList<Expression>();
+    List<Expression> lst = new ArrayList<Expression>();
 }
 {
     ( exp = expression() { lst.add(exp); } ( <PIPE> nl() exp = expression() { lst.add(exp); } )* )
@@ -249,8 +249,19 @@ StatementExpression statement() :
 
 Expression expression() :
 {
+    Expression choice;
+    List<Expression> choices = new ArrayList<Expression>();
+}
+{
+    choice = nonChoiceExpression() { choices.add(choice); }
+    ( <CHOICE> choice = nonChoiceExpression() { choices.add(choice); } )*
+    { return choices.size() == 1 ? choices.get(0) : new ChoiceExpression(choices); }
+}
+
+Expression nonChoiceExpression() :
+{
     Expression exp;
-    List<Expression> lst = new LinkedList<Expression>();
+    List<Expression> lst = new ArrayList<Expression>();
 }
 {
     ( exp = math() { lst.add(exp); } ( <DOT> exp = math() { lst.add(exp); } )* )
@@ -274,6 +285,8 @@ Expression math() :
     { return math.resolve(); }
 }
 
+
+
 Expression value() :
 {
     Expression val;
@@ -553,7 +566,7 @@ Expression randomExp() :
 
 Expression selectInputExp() :
 {
-    List<Pair<String, Expression>> cases = new LinkedList<Pair<String, Expression>>();
+    List<Pair<String, Expression>> cases = new ArrayList<Pair<String, Expression>>();
     Expression exp;
     String str;
 }
diff --git a/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/ChoiceTestCase.java b/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/ChoiceTestCase.java
new file mode 100644
index 00000000000..6e3964e644e
--- /dev/null
+++ b/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/ChoiceTestCase.java
@@ -0,0 +1,46 @@
+package com.yahoo.vespa.indexinglanguage.expressions;
+
+import com.yahoo.document.DataType;
+import com.yahoo.document.Field;
+import com.yahoo.document.datatypes.StringFieldValue;
+import com.yahoo.vespa.indexinglanguage.SimpleTestAdapter;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @author bratseth
+ */
+public class ChoiceTestCase {
+
+    @Test
+    public void testChoiceExecution() {
+        var choice = new ChoiceExpression(new InputExpression("foo"), new InputExpression("bar"));
+
+        {   // foo only
+            var adapter = new SimpleTestAdapter(new Field("foo", DataType.STRING));
+            adapter.setValue("foo", new StringFieldValue("foo1"));
+            ExecutionContext context = new ExecutionContext(adapter);
+            choice.execute(context);
+            assertEquals("foo1", context.getValue().getWrappedValue());
+        }
+
+        {   // bar only
+            var adapter = new SimpleTestAdapter(new Field("bar", DataType.STRING));
+            adapter.setValue("bar", new StringFieldValue("bar1"));
+            ExecutionContext context = new ExecutionContext(adapter);
+            choice.execute(context);
+            assertEquals("bar1", context.getValue().getWrappedValue());
+        }
+
+        {   // both foo and bar
+            var adapter = new SimpleTestAdapter(new Field("foo", DataType.STRING), new Field("bar", DataType.STRING));
+            adapter.setValue("foo", new StringFieldValue("foo1"));
+            adapter.setValue("bar", new StringFieldValue("bar1"));
+            ExecutionContext context = new ExecutionContext(adapter);
+            choice.execute(context);
+            assertEquals("foo1", context.getValue().getWrappedValue());
+        }
+    }
+
+}
diff --git a/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/ExactTestCase.java b/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/ExactTestCase.java
index 68661c7b341..e993f6cbdee 100644
--- a/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/ExactTestCase.java
+++ b/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/ExactTestCase.java
@@ -21,7 +21,7 @@ public class ExactTestCase {
     @Test
     public void requireThatHashCodeAndEqualsAreImplemented() {
         Expression exp = new ExactExpression();
-        assertFalse(exp.equals(new Object()));
+        assertNotEquals(exp, new Object());
         assertEquals(exp, new ExactExpression());
         assertEquals(exp.hashCode(), new ExactExpression().hashCode());
     }
diff --git a/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/InputTestCase.java b/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/InputTestCase.java
index 5752c373001..fe16e8d10ab 100644
--- a/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/InputTestCase.java
+++ b/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/expressions/InputTestCase.java
@@ -24,15 +24,9 @@ public class InputTestCase {
 
     @Test
     public void requireThatHashCodeAndEqualsAreImplemented() {
-        Expression exp = new InputExpression(null);
-        assertFalse(exp.equals(new Object()));
-        assertFalse(exp.equals(new InputExpression("foo")));
-        assertEquals(exp, new InputExpression(null));
-        assertEquals(exp.hashCode(), new InputExpression(null).hashCode());
-
-        exp = new InputExpression("foo");
-        assertFalse(exp.equals(new Object()));
-        assertFalse(exp.equals(new InputExpression("bar")));
+        Expression exp = new InputExpression("foo");
+        assertNotEquals(exp, new Object());
+        assertNotEquals(exp, new InputExpression("bar"));
         assertEquals(exp, new InputExpression("foo"));
         assertEquals(exp.hashCode(), new InputExpression("foo").hashCode());
     }
diff --git a/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/parser/ExpressionTestCase.java b/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/parser/ExpressionTestCase.java
index 7db026d43ee..551f770a01e 100644
--- a/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/parser/ExpressionTestCase.java
+++ b/indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/parser/ExpressionTestCase.java
@@ -37,7 +37,7 @@ public class ExpressionTestCase {
         assertExpression(IfThenExpression.class, "if (1 < 2) { 3 }");
         assertExpression(IfThenExpression.class, "if (1 < 2) { 3 } else { 4 }");
         assertExpression(IndexExpression.class, "index");
-        assertExpression(InputExpression.class, "input");
+        assertExpression(InputExpression.class, "input foo");
         assertExpression(InputExpression.class, "input field1");
         assertExpression(JoinExpression.class, "join '1'");
         assertExpression(LowerCaseExpression.class, "lowercase");
@@ -81,6 +81,7 @@ public class ExpressionTestCase {
         assertExpression(ToWsetExpression.class, "to_wset remove_if_zero create_if_non_existent");
         assertExpression(TrimExpression.class, "trim");
         assertExpression(ZCurveExpression.class, "zcurve");
+        assertExpression(ChoiceExpression.class, "input foo || \"\"");
     }
 
     private static void assertExpression(Class expectedClass, String str) throws ParseException {