From 8e8e89a1193e33a4deab6eb5d91b48266dc67922 Mon Sep 17 00:00:00 2001
From: JoostK <joost.koehoorn@gmail.com>
Date: Fri, 1 Mar 2019 00:52:22 +0100
Subject: [PATCH] fix(common): prevent repeated application of HttpParams
 mutations (#29045)

Previously, an instance of HttpParams would retain its list of mutations
after they have been materialized as a result of a read operation. Not
only does this unnecessarily hold onto memory, more importantly does it
introduce a bug where branching of off a materialized instance would
reconsider the set of mutations that had already been applied, resulting
in repeated application of mutations.

This commit fixes the bug by clearing the list of pending mutations
after they have been materialized, such that they will not be considered
once again for branched off instances.

Fixes #20430

PR Close #29045
---
 packages/common/http/src/params.ts       | 2 +-
 packages/common/http/test/params_spec.ts | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/packages/common/http/src/params.ts b/packages/common/http/src/params.ts
index 60a71ef2d0..4298b6d49e 100755
--- a/packages/common/http/src/params.ts
+++ b/packages/common/http/src/params.ts
@@ -227,7 +227,7 @@ export class HttpParams {
             }
         }
       });
-      this.cloneFrom = null;
+      this.cloneFrom = this.updates = null;
     }
   }
 }
diff --git a/packages/common/http/test/params_spec.ts b/packages/common/http/test/params_spec.ts
index 0e798129bd..669959c851 100644
--- a/packages/common/http/test/params_spec.ts
+++ b/packages/common/http/test/params_spec.ts
@@ -53,6 +53,15 @@ import {HttpParams} from '@angular/common/http/src/params';
         const mutated = body.delete('a', '2').delete('a', '4');
         expect(mutated.getAll('a')).toEqual(['1', '3', '5']);
       });
+
+      it('should not repeat mutations that have already been materialized', () => {
+        const body = new HttpParams({fromString: 'a=b'});
+        const mutated = body.append('a', 'c');
+        expect(mutated.toString()).toEqual('a=b&a=c');
+        const mutated2 = mutated.append('c', 'd');
+        expect(mutated.toString()).toEqual('a=b&a=c');
+        expect(mutated2.toString()).toEqual('a=b&a=c&c=d');
+      });
     });
 
     describe('read operations', () => {