Fix deduplication results displaying wrong data (#15755)

The log rows were mutated in the store, what resulted in wrong deduplication results as well as made the selector memoization quirky - for "the same results" the selector was running twice. 

public/app/core/logs_model.ts

@@ -245,12 +245,13 @@ export function dedupLogRows(logs: LogsModel, strategy: LogsDedupStrategy): Logs
   }
 
   const dedupedRows = logs.rows.reduce((result: LogRowModel[], row: LogRowModel, index, list) => {
+    const rowCopy = { ...row };
     const previous = result[result.length - 1];
     if (index > 0 && isDuplicateRow(row, previous, strategy)) {
       previous.duplicates++;
     } else {
-      row.duplicates = 0;
-      result.push(row);
+      rowCopy.duplicates = 0;
+      result.push(rowCopy);
     }
     return result;
   }, []);

public/app/core/specs/logs_model.test.ts

@@ -113,6 +113,34 @@ describe('dedupLogRows()', () => {
       },
     ]);
   });
+
+  test('should return to non-deduped state on same log result', () => {
+    const logs = {
+      rows: [
+        {
+          entry: 'INFO 123',
+        },
+        {
+          entry: 'WARN 123',
+        },
+        {
+          entry: 'WARN 123',
+        },
+      ],
+    };
+    expect(dedupLogRows(logs as LogsModel, LogsDedupStrategy.exact).rows).toEqual([
+      {
+        duplicates: 0,
+        entry: 'INFO 123',
+      },
+      {
+        duplicates: 1,
+        entry: 'WARN 123',
+      },
+    ]);
+
+    expect(dedupLogRows(logs as LogsModel, LogsDedupStrategy.none).rows).toEqual(logs.rows);
+  });
 });
 
 describe('calculateFieldStats()', () => {

public/app/features/explore/state/selectors.test.ts

+import { deduplicatedLogsSelector } from './selectors';
+import { LogsDedupStrategy } from 'app/core/logs_model';
+import { ExploreItemState } from 'app/types';
+
+const state = {
+  logsResult: {
+    rows: [
+      {
+        entry: '2019-03-05T11:00:56Z sntpc sntpc[1]: offset=-0.033938, delay=0.000649',
+      },
+      {
+        entry: '2019-03-05T11:00:26Z sntpc sntpc[1]: offset=-0.033730, delay=0.000581',
+      },
+      {
+        entry: '2019-03-05T10:59:56Z sntpc sntpc[1]: offset=-0.034184, delay=0.001089',
+      },
+      {
+        entry: '2019-03-05T10:59:26Z sntpc sntpc[1]: offset=-0.033972, delay=0.000582',
+      },
+      {
+        entry: '2019-03-05T10:58:56Z sntpc sntpc[1]: offset=-0.033955, delay=0.000606',
+      },
+      {
+        entry: '2019-03-05T10:58:26Z sntpc sntpc[1]: offset=-0.034067, delay=0.000616',
+      },
+      {
+        entry: '2019-03-05T10:57:56Z sntpc sntpc[1]: offset=-0.034155, delay=0.001021',
+      },
+      {
+        entry: '2019-03-05T10:57:26Z sntpc sntpc[1]: offset=-0.035797, delay=0.000883',
+      },
+      {
+        entry: '2019-03-05T10:56:56Z sntpc sntpc[1]: offset=-0.046818, delay=0.000605',
+      },
+      {
+        entry: '2019-03-05T10:56:26Z sntpc sntpc[1]: offset=-0.049200, delay=0.000584',
+      },
+    ],
+  },
+  hiddenLogLevels: undefined,
+  dedupStrategy: LogsDedupStrategy.none,
+};
+
+describe('Deduplication selector', () => {
+  it('should correctly deduplicate log rows when changing strategy multiple times', () => {
+    // Simulating sequence of UI actions that was causing a problem with deduplication counter being visible when unnecessary.
+    // The sequence was changing dedup strategy: (none -> exact -> numbers -> signature -> none) *2 -> exact. After that the first
+    // row contained information that was deduped, while it shouldn't be.
+    // Problem was caused by mutating the log results entries in redux state. The memoisation hash for deduplicatedLogsSelector
+    // was changing depending on duplicates information from log row state, while should be dependand on log row only.
+
+    let dedups = deduplicatedLogsSelector(state as ExploreItemState);
+    expect(dedups.rows.length).toBe(10);
+
+    deduplicatedLogsSelector({
+      ...state,
+      dedupStrategy: LogsDedupStrategy.none,
+    } as ExploreItemState);
+
+    deduplicatedLogsSelector({
+      ...state,
+      dedupStrategy: LogsDedupStrategy.exact,
+    } as ExploreItemState);
+
+    deduplicatedLogsSelector({
+      ...state,
+      dedupStrategy: LogsDedupStrategy.numbers,
+    } as ExploreItemState);
+
+    deduplicatedLogsSelector({
+      ...state,
+      dedupStrategy: LogsDedupStrategy.signature,
+    } as ExploreItemState);
+
+    deduplicatedLogsSelector({
+      ...state,
+      dedupStrategy: LogsDedupStrategy.none,
+    } as ExploreItemState);
+
+    deduplicatedLogsSelector({
+      ...state,
+      dedupStrategy: LogsDedupStrategy.exact,
+    } as ExploreItemState);
+
+    deduplicatedLogsSelector({
+      ...state,
+      dedupStrategy: LogsDedupStrategy.numbers,
+    } as ExploreItemState);
+
+    deduplicatedLogsSelector({
+      ...state,
+      dedupStrategy: LogsDedupStrategy.signature,
+    } as ExploreItemState);
+
+    deduplicatedLogsSelector({
+      ...state,
+      dedupStrategy: LogsDedupStrategy.none,
+    } as ExploreItemState);
+
+    dedups = deduplicatedLogsSelector({
+      ...state,
+      dedupStrategy: LogsDedupStrategy.exact,
+    } as ExploreItemState);
+
+    // Expecting that no row has duplicates now
+    expect(dedups.rows.reduce((acc, row) => acc + row.duplicates, 0)).toBe(0);
+  });
+});