[Lens] Allow number formatting within Lens

src/plugins/data/common/field_formats/types.ts

@@ -83,6 +83,7 @@ export type IFieldFormatId = FIELD_FORMAT_IDS | string;
 
 export type IFieldFormatType = (new (params?: any, getConfig?: GetConfigFn) => FieldFormat) & {
   id: IFieldFormatId;
+  title?: string;
   fieldType: string | string[];
 };
 

x-pack/legacy/plugins/lens/public/editor_frame_plugin/format_column.ts

@@ -0,0 +1,95 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { i18n } from '@kbn/i18n';
+import { ExpressionFunction, KibanaDatatable } from 'src/plugins/expressions/public';
+
+interface FormatColumn {
+  format: string;
+  columnId: string;
+  maxDecimals?: number;
+}
+
+const supportedFormats: Record<string, { decimalsToPattern: (decimals?: number) => string }> = {
+  number: {
+    decimalsToPattern: (decimals = 3) => {
+      if (decimals === 0) {
+        return `0,0`;
+      }
+      return `0,0.[${'0'.repeat(decimals)}]`;
+    },
+  },
+  percent: {
+    decimalsToPattern: (decimals = 3) => {
+      if (decimals === 0) {
+        return `0,0%`;
+      }
+      return `0,0.[${'0'.repeat(decimals)}]%`;
+    },
+  },
+  bytes: {
+    decimalsToPattern: (decimals = 3) => {
+      if (decimals === 0) {
+        return `0,0b`;
+      }
+      return `0,0.[${'0'.repeat(decimals)}]b`;
+    },
+  },
+};
+
+export const formatColumn: ExpressionFunction<
+  'lens_format_column',
+  KibanaDatatable,
+  FormatColumn,
+  KibanaDatatable
+> = {
+  name: 'lens_format_column',
+  type: 'kibana_datatable',
+  help: i18n.translate('xpack.lens.functions.mergeTables.help', {
+    defaultMessage: 'A helper to merge any number of kibana tables into a single table',
+  }),
+  args: {
+    format: {
+      types: ['string'],
+      help: '',
+    },
+    columnId: {
+      types: ['string'],
+      help: '',
+    },
+    maxDecimals: {
+      types: ['number'],
+      help: '',
+    },
+  },
+  context: {
+    types: ['kibana_datatable'],
+  },
+  fn(ctx, { format, columnId, maxDecimals }: FormatColumn) {
+    return {
+      ...ctx,
+      columns: ctx.columns.map(col => {
+        if (col.id === columnId) {
+          if (supportedFormats[format]) {
+            return {
+              ...col,
+              formatHint: {
+                id: format,
+                params: { pattern: supportedFormats[format].decimalsToPattern(maxDecimals) },
+              },
+            };
+          } else {
+            return {
+              ...col,
+              formatHint: { id: format, params: {} },
+            };
+          }
+        }
+        return col;
+      }),
+    };
+  },
+};

x-pack/legacy/plugins/lens/public/editor_frame_plugin/plugin.tsx

@@ -31,6 +31,7 @@ import {
 } from '../types';
 import { EditorFrame } from './editor_frame';
 import { mergeTables } from './merge_tables';
+import { formatColumn } from './format_column';
 import { EmbeddableFactory } from './embeddable/embeddable_factory';
 import { getActiveDatasourceIdFromDoc } from './editor_frame/state_management';
 
@@ -55,6 +56,7 @@ export class EditorFramePlugin {
 
   public setup(core: CoreSetup, plugins: EditorFrameSetupPlugins): EditorFrameSetup {
     plugins.expressions.registerFunction(() => mergeTables);
+    plugins.expressions.registerFunction(() => formatColumn);
 
     return {
       registerDatasource: datasource => {