Improve error message for empty ColumnAggregation(s) (#3242)

Provides better developer experience, see #3235
deephaven · Jan 11, 2023 · 845f50d · 845f50d
1 parent c4dfb04
commit 845f50d
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Showing 3 changed files with 14 additions and 4 deletions.
diff --git a/table-api/src/main/java/io/deephaven/api/agg/Aggregation.java b/table-api/src/main/java/io/deephaven/api/agg/Aggregation.java
@@ -72,6 +72,10 @@ static Aggregation of(AggSpec spec, String... pairs) {
      * @return The aggregation
      */
     static Aggregation of(AggSpec spec, List<String> pairs) {
+        if (pairs.isEmpty()) {
+            throw new IllegalArgumentException(
+                    "Must have at least one pair to create an Aggregation from an AggSpec. Did you mean to use TableOperations#aggAllBy?");
+        }
         if (pairs.size() == 1) {
             return of(spec, pairs.get(0));
         }
@@ -89,6 +93,9 @@ static Aggregation of(AggSpec spec, List<String> pairs) {
      * @return The combined aggregation
      */
     static Aggregation of(Aggregation... aggregations) {
+        if (aggregations.length == 0) {
+            throw new IllegalArgumentException("Unable to create an empty aggregation.");
+        }
         if (aggregations.length == 1) {
             return aggregations[0];
         }
@@ -108,6 +115,9 @@ static Aggregation of(Aggregation... aggregations) {
     @SafeVarargs
     static <INPUT_TYPE> Aggregation of(BiFunction<ColumnName, INPUT_TYPE, ColumnAggregation> columnAggFactory,
             String inputColumn, INPUT_TYPE... inputs) {
+        if (inputs.length == 0) {
+            throw new IllegalArgumentException("Unable to create an empty aggregation.");
+        }
         final ColumnName inputColumnName = ColumnName.of(inputColumn);
         if (inputs.length == 1) {
             return columnAggFactory.apply(inputColumnName, inputs[0]);

diff --git a/table-api/src/main/java/io/deephaven/api/agg/Aggregations.java b/table-api/src/main/java/io/deephaven/api/agg/Aggregations.java
@@ -32,8 +32,8 @@ public final <V extends Visitor> V walk(V visitor) {
     @Check
     final void checkSize() {
         if (aggregations().size() < 2) {
-            throw new IllegalArgumentException(
-                    String.format("%s should have at least two aggregations", Aggregations.class));
+            throw new IllegalArgumentException(String.format("%s should have at least two aggregations, has %d",
+                    Aggregations.class, aggregations().size()));
         }
     }
 

diff --git a/table-api/src/main/java/io/deephaven/api/agg/ColumnAggregations.java b/table-api/src/main/java/io/deephaven/api/agg/ColumnAggregations.java
@@ -36,8 +36,8 @@ public final <V extends Visitor> V walk(V visitor) {
     @Check
     final void checkSize() {
         if (pairs().size() < 2) {
-            throw new IllegalArgumentException(
-                    String.format("%s should have at least two pairs", ColumnAggregations.class));
+            throw new IllegalArgumentException(String.format("%s should have at least two pairs, has %d",
+                    ColumnAggregations.class, pairs().size()));
         }
     }