Fix: Avoid glob of single-value array variables (#18420)

* Fix: Avoid glob of single-value array variables

Based on our current implementation of templates, when multi-select
variables are part of a dashboard query the default/fallback formatting option is `glob`.

Some data sources do not support glob (e.g. metrics.{a}.* instead of
metrics.a.*) for single variable queries. This behaviour breaks dashboards.

This commit introduces an alternative formatting option where globing is avoided if it's there is only one value as part of the query variable.

This means, queries previously formatted as `query=metrics.{a}.*.*`, are
now formatted as `query=metrics.a.*.*`. However, queries formatted as
`query=metrics.{a,b}.*.*` continue to be as is.

public/app/features/templating/specs/template_srv.test.ts

@@ -112,6 +112,23 @@ describe('templateSrv', () => {
       expect(target).toBe('this.{value1,value2}.filters');
     });
 
+    describe('when the globbed variable only has one value', () => {
+      beforeEach(() => {
+        initTemplateSrv([
+          {
+            type: 'query',
+            name: 'test',
+            current: { value: ['value1'] },
+          },
+        ]);
+      });
+
+      it('should not glob the value', () => {
+        const target = _templateSrv.replace('this.$test.filters', {}, 'glob');
+        expect(target).toBe('this.value1.filters');
+      });
+    });
+
     it('should replace ${test} with globbed value', () => {
       const target = _templateSrv.replace('this.${test}.filters', {}, 'glob');
       expect(target).toBe('this.{value1,value2}.filters');

public/app/features/templating/template_srv.ts

@@ -172,7 +172,7 @@ export class TemplateSrv {
         return this.encodeURIComponentStrict(value);
       }
       default: {
-        if (_.isArray(value)) {
+        if (_.isArray(value) && value.length > 1) {
           return '{' + value.join(',') + '}';
         }
         return value;

public/app/plugins/datasource/graphite/specs/datasource.test.ts

@@ -2,7 +2,7 @@ import { GraphiteDatasource } from '../datasource';
 import _ from 'lodash';
 // @ts-ignore
 import $q from 'q';
-import { TemplateSrvStub } from 'test/specs/helpers';
+import { TemplateSrv } from 'app/features/templating/template_srv';
 import { dateTime } from '@grafana/data';
 
 describe('graphiteDatasource', () => {
@@ -10,7 +10,7 @@ describe('graphiteDatasource', () => {
     backendSrv: {},
     $q,
     // @ts-ignore
-    templateSrv: new TemplateSrvStub(),
+    templateSrv: new TemplateSrv(),
     instanceSettings: { url: 'url', name: 'graphiteProd', jsonData: {} },
   };
 
@@ -218,6 +218,38 @@ describe('graphiteDatasource', () => {
       });
       expect(results.length).toBe(2);
     });
+
+    describe('when formatting targets', () => {
+      it('does not attempt to glob for one variable', () => {
+        ctx.ds.templateSrv.init([
+          {
+            type: 'query',
+            name: 'metric',
+            current: { value: ['b'] },
+          },
+        ]);
+
+        const results = ctx.ds.buildGraphiteParams({
+          targets: [{ target: 'my.$metric.*' }],
+        });
+        expect(results).toStrictEqual(['target=my.b.*', 'format=json']);
+      });
+
+      it('globs for more than one variable', () => {
+        ctx.ds.templateSrv.init([
+          {
+            type: 'query',
+            name: 'metric',
+            current: { value: ['a', 'b'] },
+          },
+        ]);
+
+        const results = ctx.ds.buildGraphiteParams({
+          targets: [{ target: 'my.[[metric]].*' }],
+        });
+        expect(results).toStrictEqual(['target=my.%7Ba%2Cb%7D.*', 'format=json']);
+      });
+    });
   });
 
   describe('querying for template variables', () => {
@@ -308,7 +340,13 @@ describe('graphiteDatasource', () => {
     });
 
     it('/metrics/find should be POST', () => {
-      ctx.templateSrv.setGrafanaVariable('foo', 'bar');
+      ctx.ds.templateSrv.init([
+        {
+          type: 'query',
+          name: 'foo',
+          current: { value: ['bar'] },
+        },
+      ]);
       ctx.ds.metricFindQuery('[[foo]]').then((data: any) => {
         results = data;
       });
@@ -327,7 +365,7 @@ function accessScenario(name: string, url: string, fn: any) {
       backendSrv: {},
       $q,
       // @ts-ignore
-      templateSrv: new TemplateSrvStub(),
+      templateSrv: new TemplateSrv(),
       instanceSettings: { url: 'url', name: 'graphiteProd', jsonData: {} },
     };