What were you doing?

1. Run an xpcshell-test which has the add-on manager enabled and enable the jsdebugger, e.g.

./mach xpcshell-test toolkit/components/search/tests/xpcshell/test_webextensions_install.js --jsdebugger

2. Via about:debugging, inspect the xpcshell-test process.
3. Press "Run" in the debugger

What happened?

Test fails with:

ERROR Unexpected exception Error: Duplicate BroadcastConduit method name recvPortConnect at resource://gre/modules/ConduitsParent.jsm:98
openConduit@resource://gre/modules/ConduitsParent.jsm:98:15
BroadcastConduit@resource://gre/modules/ConduitsParent.jsm:268:9
init@resource://gre/modules/ExtensionParent.jsm:268:20
@resource://gre/modules/ExtensionParent.jsm:402:16
@resource://gre/modules/Extension.jsm:83:41
promiseStartupManager@resource://testing-common/AddonTestUtils.jsm:774:5
setup@/Users/mark/dev/gecko/objdir-ff-opt/_tests/xpcshell/toolkit/components/search/tests/xpcshell/test_webextensions_install.js:26:9
async*_run_next_test/<@/Users/mark/dev/gecko/testing/xpcshell/head.js:1772:22
_run_next_test@/Users/mark/dev/gecko/testing/xpcshell/head.js:1772:38
run@/Users/mark/dev/gecko/testing/xpcshell/head.js:818:9
_do_main@/Users/mark/dev/gecko/testing/xpcshell/head.js:240:6
_execute_test@/Users/mark/dev/gecko/testing/xpcshell/head.js:603:5
@-e:1:1

What should have happened?

Test should have run & passed.

Anything else we should know?

Tested with the latest mozilla-central & nightly builds.

The tests start up the add-on manager, and it seems to be this that is causing a conflict.

to investigate

We have two stack trace leading to call openConduit for this method:

BroadcastConduit@resource://gre/modules/ConduitsParent.jsm:271:9
init@resource://gre/modules/ExtensionParent.jsm:268:20
@resource://gre/modules/ExtensionParent.jsm:402:16
defineLazyModuleGetter/<@resource://devtools/shared/loader/builtin-modules.js:165:26
get@resource://devtools/shared/loader/builtin-modules.js:118:28
watch@resource://devtools/server/actors/resources/extensions-backgroundscript-status.js:44:5
watchResources@resource://devtools/server/actors/resources/index.js:288:19
watchResources@resource://devtools/server/actors/root.js:562:21
handler@resource://devtools/shared/protocol/Actor.js:175:37
onPacket@resource://devtools/server/devtools-server-connection.js:379:58
_onJSONObjectReady/<@resource://devtools/shared/transport/transport.js:464:22
exports.makeInfallible/<@resource://devtools/shared/ThreadSafeDevToolsUtils.js:103:22
exports.makeInfallible/<@resource://devtools/shared/ThreadSafeDevToolsUtils.js:103:22
_initDebugging@/Users/jdescottes/Development/hg/fx-team-artifact/testing/xpcshell/head.js:495:6
_execute_test@/Users/jdescottes/Development/hg/fx-team-artifact/testing/xpcshell/head.js:546:21

and

openConduit@resource://gre/modules/ConduitsParent.jsm:97:21
BroadcastConduit@resource://gre/modules/ConduitsParent.jsm:271:9
init@resource://gre/modules/ExtensionParent.jsm:268:20
@resource://gre/modules/ExtensionParent.jsm:402:16
@resource://gre/modules/Extension.jsm:83:41
promiseStartupManager@resource://testing-common/AddonTestUtils.jsm:774:5
setup@/Users/jdescottes/Development/hg/fx-team-artifact/objdir.noindex/_tests/xpcshell/toolkit/components/search/tests/xpcshell/test_webextensions_install.js:26:9
async*_run_next_test/<@/Users/jdescottes/Development/hg/fx-team-artifact/testing/xpcshell/head.js:1772:22
_run_next_test@/Users/jdescottes/Development/hg/fx-team-artifact/testing/xpcshell/head.js:1772:38
run@/Users/jdescottes/Development/hg/fx-team-artifact/testing/xpcshell/head.js:818:9
_do_main@/Users/jdescottes/Development/hg/fx-team-artifact/testing/xpcshell/head.js:240:6
_execute_test@/Users/jdescottes/Development/hg/fx-team-artifact/testing/xpcshell/head.js:603:5

Meaning this is a regression from Bug 1748529

Luca: do you have any suggestion on how we should handle this?

Set release status flags based on info from the regressing bug 1748529

ExtensionParent.jsm is loaded twice, because the ChromeUtils.import call in the devtoools module loads a new instance of the file in the devtools samdbox at https://searchfox.org/mozilla-central/rev/be4604e4be8c71b3c1dbff2398a5b05f15411673/devtools/shared/loader/builtin-modules.js#44

ExtensionParent is referenced at
https://searchfox.org/mozilla-central/rev/be4604e4be8c71b3c1dbff2398a5b05f15411673/devtools/server/actors/resources/extensions-backgroundscript-status.js#9

So ExtensionParent.jsm is loaded again the second time because there is a failure at the first attempt. Consequently, the start of ExtensionParent.jsm runs twice.

The error at the first run is as follows:

Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIProperties.get]

at resource://gre/modules/ExtensionParent.jsm:1913:21, i.e. the call to Services.dirsvc.get("ProfLD", Ci.nsIFile) at https://searchfox.org/mozilla-central/rev/0077f2248712a1b45bf02f0f866449f663538164/toolkit/components/extensions/ExtensionParent.jsm#1911

There are two ways to fix it:

1. Is to make StartupCache.file a lazy getter so that Services.dirsvc.get is called later. I confirmed that this works.
2. is to figure out why Services.dirsvc.get fails, and to see if we need to initialize dirsvc earlier or look for alternatives.

ExtensionParent.jsm cannot be loaded without a profile, as explained at
https://bugzilla.mozilla.org/show_bug.cgi?id=1761072#c5.

But ExtensionsBackgroundScriptStatusWatcher would try to (lazily) load
the module before a profile was ready, in order to subscribe to future
changes. To avoid loading this whole ExtensionParent.jsm module, I have
replaced the event propagation mechanism with observers.

https://hg.mozilla.org/mozilla-central/rev/d256dd748a15