Promtheus: Improve tab completion (#20938)

Change in behavior:

- no longer suggest everything in empty field, only history
- term suggestions need at least one character

public/app/plugins/datasource/prometheus/language_provider.test.ts

@@ -13,35 +13,24 @@ describe('Language completion provider', () => {
   } as any) as PrometheusDatasource;
 
   describe('empty query suggestions', () => {
-    it('returns default suggestions on empty context', async () => {
+    it('returns no suggestions on empty context', async () => {
       const instance = new LanguageProvider(datasource);
       const value = Plain.deserialize('');
       const result = await instance.provideCompletionItems({ text: '', prefix: '', value, wrapperClasses: [] });
       expect(result.context).toBeUndefined();
-      expect(result.suggestions).toMatchObject([
-        {
-          label: 'Functions',
-        },
-      ]);
+      expect(result.suggestions).toMatchObject([]);
     });
 
-    it('returns default suggestions with metrics on empty context when metrics were provided', async () => {
+    it('returns no suggestions with metrics on empty context even when metrics were provided', async () => {
       const instance = new LanguageProvider(datasource);
       instance.metrics = ['foo', 'bar'];
       const value = Plain.deserialize('');
       const result = await instance.provideCompletionItems({ text: '', prefix: '', value, wrapperClasses: [] });
       expect(result.context).toBeUndefined();
-      expect(result.suggestions).toMatchObject([
-        {
-          label: 'Functions',
-        },
-        {
-          label: 'Metrics',
-        },
-      ]);
+      expect(result.suggestions).toMatchObject([]);
     });
 
-    it('returns default suggestions with history on empty context when history was provided', async () => {
+    it('returns history on empty context when history was provided', async () => {
       const instance = new LanguageProvider(datasource);
       const value = Plain.deserialize('');
       const history: Array<HistoryItem<PromQuery>> = [
@@ -65,9 +54,6 @@ describe('Language completion provider', () => {
             },
           ],
         },
-        {
-          label: 'Functions',
-        },
       ]);
     });
   });
@@ -101,14 +87,31 @@ describe('Language completion provider', () => {
   });
 
   describe('metric suggestions', () => {
-    it('returns metrics and function suggestions in an unknown context', async () => {
+    it('returns history, metrics and function suggestions in an uknown context ', async () => {
       const instance = new LanguageProvider(datasource);
       instance.metrics = ['foo', 'bar'];
+      const history: Array<HistoryItem<PromQuery>> = [
+        {
+          ts: 0,
+          query: { refId: '1', expr: 'metric' },
+        },
+      ];
       let value = Plain.deserialize('a');
       value = value.setSelection({ anchor: { offset: 1 }, focus: { offset: 1 } });
-      const result = await instance.provideCompletionItems({ text: 'a', prefix: 'a', value, wrapperClasses: [] });
+      const result = await instance.provideCompletionItems(
+        { text: 'm', prefix: 'm', value, wrapperClasses: [] },
+        { history }
+      );
       expect(result.context).toBeUndefined();
       expect(result.suggestions).toMatchObject([
+        {
+          label: 'History',
+          items: [
+            {
+              label: 'metric',
+            },
+          ],
+        },
         {
           label: 'Functions',
         },
@@ -118,12 +121,28 @@ describe('Language completion provider', () => {
       ]);
     });
 
-    it('returns metrics and function  suggestions after a binary operator', async () => {
+    it('returns no suggestions directly after a binary operator', async () => {
       const instance = new LanguageProvider(datasource);
       instance.metrics = ['foo', 'bar'];
       const value = Plain.deserialize('*');
       const result = await instance.provideCompletionItems({ text: '*', prefix: '', value, wrapperClasses: [] });
       expect(result.context).toBeUndefined();
+      expect(result.suggestions).toMatchObject([]);
+    });
+
+    it('returns metric suggestions with prefix after a binary operator', async () => {
+      const instance = new LanguageProvider(datasource);
+      instance.metrics = ['foo', 'bar'];
+      const value = Plain.deserialize('foo + b');
+      const ed = new SlateEditor({ value });
+      const valueWithSelection = ed.moveForward(7).value;
+      const result = await instance.provideCompletionItems({
+        text: 'foo + b',
+        prefix: 'b',
+        value: valueWithSelection,
+        wrapperClasses: [],
+      });
+      expect(result.context).toBeUndefined();
       expect(result.suggestions).toMatchObject([
         {
           label: 'Functions',

public/app/plugins/datasource/prometheus/language_provider.ts

@@ -72,7 +72,14 @@ export default class PromQlLanguageProvider extends LanguageProvider {
   }
 
   // Strip syntax chars
-  cleanText = (s: string) => s.replace(/[{}[\]="(),!~+\-*/^%]/g, '').trim();
+  cleanText = (s: string) =>
+    s
+      .replace(/[{}[\]="(),!]/g, '')
+      .replace(/^\s*[~+\-*/^%]/, '')
+      .trim()
+      .split(' ')
+      .pop()
+      .trim();
 
   get syntax() {
     return PromqlSyntax;
@@ -126,7 +133,7 @@ export default class PromQlLanguageProvider extends LanguageProvider {
     const noSuffix = !nextCharacter || nextCharacter === ')';
 
     // Empty prefix is safe if it does not immediately follow a complete expression and has no text after it
-    const safeEmptyPrefix = prefix === '' && !text.match(/^[\]})\s]+$/) && noSuffix;
+    const safePrefix = prefix && !text.match(/^[\]})\s]+$/) && noSuffix;
 
     // About to type next operand if preceded by binary operator
     const operatorsPattern = /[+\-*/^%]/;
@@ -145,7 +152,10 @@ export default class PromQlLanguageProvider extends LanguageProvider {
     } else if (empty) {
       // Suggestions for empty query field
       return this.getEmptyCompletionItems(context);
-    } else if ((prefixUnrecognized && noSuffix) || safeEmptyPrefix || isNextOperand) {
+    } else if (prefixUnrecognized && noSuffix && !isNextOperand) {
+      // Show term suggestions in a couple of scenarios
+      return this.getBeginningCompletionItems(context);
+    } else if (prefixUnrecognized && safePrefix) {
       // Show term suggestions in a couple of scenarios
       return this.getTermCompletionItems();
     }
@@ -155,6 +165,12 @@ export default class PromQlLanguageProvider extends LanguageProvider {
     };
   };
 
+  getBeginningCompletionItems = (context: { history: Array<HistoryItem<PromQuery>> }): TypeaheadOutput => {
+    return {
+      suggestions: [...this.getEmptyCompletionItems(context).suggestions, ...this.getTermCompletionItems().suggestions],
+    };
+  };
+
   getEmptyCompletionItems = (context: { history: Array<HistoryItem<PromQuery>> }): TypeaheadOutput => {
     const { history } = context;
     const suggestions = [];
@@ -177,9 +193,6 @@ export default class PromQlLanguageProvider extends LanguageProvider {
       });
     }
 
-    const termCompletionItems = this.getTermCompletionItems();
-    suggestions.push(...termCompletionItems.suggestions);
-
     return { suggestions };
   };