DisplayProcessor: Show strings as strings (#27097)

* WIP: strings and numbers

* Works in displayProcessor but units are not applied in applyFieldOverride

* removed bit

* Updated

* Added docs

* fixed typo

docs/sources/panels/field-configuration-options.md

@@ -156,13 +156,13 @@ When multiple stats, fields, or series are shown, this field controls the title
 
 Given a field with a name of Temp, and labels of {"Loc"="PBI", "Sensor"="3"}
 
-| Expression syntax            | Example                | Renders to                        | Explanation |
-| ---------------------------- | ---------------------- | --------------------------------- | ----------- |
-| `${__field.displayName}`     | Same as syntax         | `Temp {Loc="PBI", Sensor="3"}`    | Displays the field name, and labels in `{}` if they are present. If there is only one label key in the response, then for the label portion, Grafana displays the value of the label without the enclosing braces. |
-| `${__field.name}`            | Same as syntax          | `Temp`                           | Displays the name of the field (without labels). |
-| `${__field.labels}`          | Same as syntax          | `Loc="PBI", Sensor="3"`          | Displays the labels without the name. |
-| `${__field.labels.X}`        | `${__field.labels.Loc}` | `PBI`                            | Displays the value of the specified label key. |
-| `${__field.labels.__values}` | Same as Syntax          | `PBI, 3`                         | Displays the values of the labels separated by a comma (without label keys). |
+| Expression syntax            | Example                 | Renders to                     | Explanation                                                                                                                                                                                                        |
+| ---------------------------- | ----------------------- | ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
+| `${__field.displayName}`     | Same as syntax          | `Temp {Loc="PBI", Sensor="3"}` | Displays the field name, and labels in `{}` if they are present. If there is only one label key in the response, then for the label portion, Grafana displays the value of the label without the enclosing braces. |
+| `${__field.name}`            | Same as syntax          | `Temp`                         | Displays the name of the field (without labels).                                                                                                                                                                   |
+| `${__field.labels}`          | Same as syntax          | `Loc="PBI", Sensor="3"`        | Displays the labels without the name.                                                                                                                                                                              |
+| `${__field.labels.X}`        | `${__field.labels.Loc}` | `PBI`                          | Displays the value of the specified label key.                                                                                                                                                                     |
+| `${__field.labels.__values}` | Same as Syntax          | `PBI, 3`                       | Displays the values of the labels separated by a comma (without label keys).                                                                                                                                       |
 
 If the value is an empty string after rendering the expression for a particular field, then the default display method is used.
 
@@ -201,6 +201,11 @@ You can also paste a native emoji in the unit picker and pick it as a custom uni
 
 {{< docs-imagebox img="/img/docs/v66/custom_unit_burger2.png" max-width="600px" caption="Custom unit emoji" >}}
 
+#### String unit
+
+Grafana can sometime be too aggressive in parsing strings and displaying them as numbers. To make Grafana show the original
+string create a field override and add a unit property with the `string` unit.
+
 ### Thresholds
 
 Thresholds allow you to change the color of a field based on the value.

docs/sources/panels/visualizations/table-panel.md

@@ -26,3 +26,10 @@ Table visualizations allow you to apply:
 ## Display options
 
 - **Show header -** Show or hide column names imported from your data source..
+
+## Tips
+
+### Display original string value
+
+Grafana can sometime be too aggressive in parsing strings and displaying them as numbers. To make Grafana show the original
+string create a field override and add a unit property with the `string` unit.

packages/grafana-data/src/field/displayProcessor.test.ts

@@ -303,4 +303,26 @@ describe('Date display options', () => {
 
     expect(processor('2020-08-01T08:48:43.783337Z').text).toEqual('2020-08-01 08:48:43');
   });
+
+  describe('number formatting for string values', () => {
+    it('should preserve string unchanged if unit is strings', () => {
+      const processor = getDisplayProcessor({
+        field: {
+          type: FieldType.string,
+          config: { unit: 'string' },
+        },
+      });
+      expect(processor('22.1122334455').text).toEqual('22.1122334455');
+    });
+
+    it('should format string as number if no unit', () => {
+      const processor = getDisplayProcessor({
+        field: {
+          type: FieldType.string,
+          config: { decimals: 2 },
+        },
+      });
+      expect(processor('22.1122334455').text).toEqual('22.11');
+    });
+  });
 });

packages/grafana-data/src/field/displayProcessor.ts

@@ -46,13 +46,14 @@ export function getDisplayProcessor(options?: DisplayProcessorOptions): DisplayP
 
   return (value: any) => {
     const { mappings } = config;
+    const isStringUnit = unit === 'string';
 
     if (hasDateUnit && typeof value === 'string') {
       value = dateTime(value).valueOf();
     }
 
     let text = _.toString(value);
-    let numeric = toNumber(value);
+    let numeric = isStringUnit ? NaN : toNumber(value);
     let prefix: string | undefined = undefined;
     let suffix: string | undefined = undefined;
     let shouldFormat = true;
@@ -62,7 +63,7 @@ export function getDisplayProcessor(options?: DisplayProcessorOptions): DisplayP
 
       if (mappedValue) {
         text = mappedValue.text;
-        const v = toNumber(text);
+        const v = isStringUnit ? NaN : toNumber(text);
 
         if (!isNaN(v)) {
           numeric = v;

packages/grafana-data/src/valueFormats/categories.ts

@@ -1,4 +1,4 @@
-import { locale, scaledUnits, simpleCountUnit, toFixedUnit, ValueFormatCategory } from './valueFormats';
+import { locale, scaledUnits, simpleCountUnit, toFixedUnit, ValueFormatCategory, stringFormater } from './valueFormats';
 import {
   dateTimeAsIso,
   dateTimeAsUS,
@@ -26,19 +26,20 @@ export const getCategories = (): ValueFormatCategory[] => [
     name: 'Misc',
     formats: [
       { name: 'none', id: 'none', fn: toFixedUnit('') },
+      { name: 'String', id: 'string', fn: stringFormater },
       {
         name: 'short',
         id: 'short',
         fn: scaledUnits(1000, ['', ' K', ' Mil', ' Bil', ' Tri', ' Quadr', ' Quint', ' Sext', ' Sept']),
       },
-      { name: 'percent (0-100)', id: 'percent', fn: toPercent },
-      { name: 'percent (0.0-1.0)', id: 'percentunit', fn: toPercentUnit },
+      { name: 'Percent (0-100)', id: 'percent', fn: toPercent },
+      { name: 'Percent (0.0-1.0)', id: 'percentunit', fn: toPercentUnit },
       { name: 'Humidity (%H)', id: 'humidity', fn: toFixedUnit('%H') },
-      { name: 'decibel', id: 'dB', fn: toFixedUnit('dB') },
-      { name: 'hexadecimal (0x)', id: 'hex0x', fn: toHex0x },
-      { name: 'hexadecimal', id: 'hex', fn: toHex },
-      { name: 'scientific notation', id: 'sci', fn: sci },
-      { name: 'locale format', id: 'locale', fn: locale },
+      { name: 'Decibel', id: 'dB', fn: toFixedUnit('dB') },
+      { name: 'Hexadecimal (0x)', id: 'hex0x', fn: toHex0x },
+      { name: 'Hexadecimal', id: 'hex', fn: toHex },
+      { name: 'Scientific notation', id: 'sci', fn: sci },
+      { name: 'Locale format', id: 'locale', fn: locale },
       { name: 'Pixels', id: 'pixel', fn: toFixedUnit('px') },
     ],
   },

packages/grafana-data/src/valueFormats/valueFormats.ts

@@ -156,6 +156,10 @@ export function simpleCountUnit(symbol: string): ValueFormatter {
   };
 }
 
+export function stringFormater(value: number): FormattedValue {
+  return { text: `${value}` };
+}
+
 function buildFormats() {
   categories = getCategories();