Transformations: Add applicability function to group to nested table (#85501)

* Add applicability function to group to nested table

* codeincarnate/group-to-nested-cond/ run linter

---------

Co-authored-by: jev forsberg <jev.forsberg@grafana.com>

packages/grafana-data/src/transformations/transformers/groupBy.ts

@@ -7,6 +7,9 @@ import { DataTransformerInfo } from '../../types/transformations';
 import { reduceField, ReducerID } from '../fieldReducer';
 
 import { DataTransformerID } from './ids';
+import { findMaxFields } from './utils';
+
+const MINIMUM_FIELDS_REQUIRED = 2;
 
 export enum GroupByOperationID {
   aggregate = 'aggregate',
@@ -34,32 +37,19 @@ export const groupByTransformer: DataTransformerInfo<GroupByTransformerOptions>
     fields: {},
   },
   isApplicable: (data: DataFrame[]) => {
-    let maxFields = 0;
-
     // Group by needs at least two fields
     // a field to group on and a field to aggregate
     // We make sure that at least one frame has at
     // least two fields
-    for (const frame of data) {
-      if (frame.fields.length > maxFields) {
-        maxFields = frame.fields.length;
-      }
-    }
+    const maxFields = findMaxFields(data);
 
-    return maxFields >= 2
+    return maxFields >= MINIMUM_FIELDS_REQUIRED
       ? TransformationApplicabilityLevels.Applicable
       : TransformationApplicabilityLevels.NotApplicable;
   },
   isApplicableDescription: (data: DataFrame[]) => {
-    let maxFields = 0;
-
-    for (const frame of data) {
-      if (frame.fields.length > maxFields) {
-        maxFields = frame.fields.length;
-      }
-    }
-
-    return `The Group by transformation requires a series with at least two fields to work. The maximum number of fields found on a series is ${maxFields}`;
+    const maxFields = findMaxFields(data);
+    return `The Group by transformation requires a series with at least ${MINIMUM_FIELDS_REQUIRED} fields to work. The maximum number of fields found on a series is ${maxFields}`;
   },
   /**
    * Return a modified copy of the series. If the transform is not or should not

packages/grafana-data/src/transformations/transformers/groupToNestedTable.ts

@@ -3,13 +3,15 @@ import { map } from 'rxjs/operators';
 import { guessFieldTypeForField } from '../../dataframe/processDataFrame';
 import { getFieldDisplayName } from '../../field/fieldState';
 import { DataFrame, Field, FieldType } from '../../types/dataFrame';
-import { DataTransformerInfo } from '../../types/transformations';
+import { DataTransformerInfo, TransformationApplicabilityLevels } from '../../types/transformations';
 import { ReducerID, reduceField } from '../fieldReducer';
 
 import { GroupByFieldOptions, createGroupedFields, groupValuesByKey } from './groupBy';
 import { DataTransformerID } from './ids';
+import { findMaxFields } from './utils';
 
 export const SHOW_NESTED_HEADERS_DEFAULT = true;
+const MINIMUM_FIELDS_REQUIRED = 2;
 
 enum GroupByOperationID {
   aggregate = 'aggregate',
@@ -33,7 +35,19 @@ export const groupToNestedTable: DataTransformerInfo<GroupToNestedTableTransform
     showSubframeHeaders: SHOW_NESTED_HEADERS_DEFAULT,
     fields: {},
   },
-
+  isApplicable: (data) => {
+    // Group to nested table needs at least two fields
+    // a field to group on and to show in the nested table
+    const maxFields = findMaxFields(data);
+
+    return maxFields >= MINIMUM_FIELDS_REQUIRED
+      ? TransformationApplicabilityLevels.Applicable
+      : TransformationApplicabilityLevels.NotApplicable;
+  },
+  isApplicableDescription: (data: DataFrame[]) => {
+    const maxFields = findMaxFields(data);
+    return `The Group to nested table transformation requires a series with at least ${MINIMUM_FIELDS_REQUIRED} fields to work. The maximum number of fields found on a series is ${maxFields}`;
+  },
   /**
    * Return a modified copy of the series. If the transform is not or should not
    * be applied, just return the input series

packages/grafana-data/src/transformations/transformers/utils.ts

@@ -1,3 +1,22 @@
+import { DataFrame } from '../../types';
+
 export const transformationsVariableSupport = () => {
   return (window as any)?.grafanaBootData?.settings?.featureToggles?.transformationsVariableSupport;
 };
+
+/**
+ * Retrieve the maximum number of fields in a series of a dataframe.
+ */
+export function findMaxFields(data: DataFrame[]) {
+  let maxFields = 0;
+
+  // Group to nested table needs at least two fields
+  // a field to group on and to show in the nested table
+  for (const frame of data) {
+    if (frame.fields.length > maxFields) {
+      maxFields = frame.fields.length;
+    }
+  }
+
+  return maxFields;
+}