Don't let the platform be changed after Glean was initialized

Author: brizental

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 [Full changelog](https://github.com/mozilla/glean.js/compare/v0.8.0...main)
 
+* [#201](https://github.com/mozilla/glean.js/pull/201): BUGFIX: Do not let the platform be changed after Glean is initialized.
 # v0.8.0 (2021-04-13)
 
 [Full changelog](https://github.com/mozilla/glean.js/compare/v0.7.0...v0.8.0)

glean/src/core/glean.ts

@@ -443,6 +443,14 @@ class Glean {
    *        Please check out the available environments in the platform/ module.
    */
   static setPlatform(platform: Platform): void {
+    if (Context.initialized) {
+      console.info(
+        "Attempted to set the platform but Glean has already been initialized. Ignoring.",
+        `Current platform is: ${Glean.platform.name}}`
+      );
+      return;
+    }
+
     Glean.instance._platform = platform;
   }
 

glean/src/platform/index.ts

@@ -20,6 +20,8 @@ interface Platform {
   uploader: Uploader,
   // The environment specifici implemtation of platform information getters
   info: PlatformInfo,
+  // The name of the platform, useful for logging and debugging purposes.
+  name: string,
 }
 
 export default Platform;

glean/src/platform/test/index.ts

@@ -43,6 +43,7 @@ const TestPlatform: Platform = {
   Storage: MockStorage,
   uploader: new MockUploader(),
   info: MockPlatformInfo,
+  name: "test"
 };
 
 export default TestPlatform;

glean/src/platform/webext/index.ts

@@ -12,6 +12,7 @@ const WebExtPlatform: Platform = {
   Storage,
   uploader,
   info,
+  name: "webext"
 };
 
 export default WebExtPlatform;

glean/tests/core/glean.spec.ts

@@ -514,4 +514,15 @@ describe("Glean", function() {
       [1,2,3,4,5,6,7,8,9,10]
     );
   });
+
+  it("disallow changing the platform after Glean is initialized", async function() {
+    const MockPlatform = {
+      ...TestPlatform,
+      name: "mock"
+    };
+
+    Glean.setPlatform(MockPlatform);
+
+    assert.strictEqual(TestPlatform.name, Glean.platform.name);
+  });
 });