RDART-983: Refactor how we open dynamic library to give better error message

[nielsenko]

This PR aims to give a better error message, if we fail to load the native shared library.

In the process It changes how we attempt to open it.

First of all it only tries one place when running under the flutter vm, which is the most common scenario. This is not only more correct, but it also improves the error message on failure by not referring to unrelated paths.

Secondly, it will report a hint to add realm package if it fails. It is an easy mistake to only add realm_dart. We have seen one example already in #1595.

Fix: #1595

Sample error messages

Dart script:

dart run bin/init_realm_dart.dart
Unhandled exception:
Realm error : Could not open librealm_dart.dylib. Tried:
- "librealm_dart.dylib"
- "/Users/kasper/.puro/shared/caches/e76c956498841e1ab458577d3892003e553e4f3c/dart-sdk/bin/librealm_dart.dylib"
/Users/kasper/Projects/mongodb/experiments/init_realm_dart/binary/macos/librealm_dart.dylib
Hint: Did you forget to run `dart run realm_dart install`?
#0      _openRealmLib.throwError (package:realm_dart/src/init.dart:71:5)
#1      _openRealmLib (package:realm_dart/src/init.dart:97:5)
#2      initRealm (package:realm_dart/src/init.dart:120:24)
...

Dart pre-compiled exe:

./bin/init_realm_dart.exe
Unhandled exception:
Realm error : Could not open librealm_dart.dylib. Tried:
- "librealm_dart.dylib"
- "/Users/kasper/Projects/mongodb/experiments/init_realm_dart/bin/librealm_dart.dylib"
- "/Users/kasper/Projects/mongodb/experiments/init_realm_dart/binary/macos/librealm_dart.dylib"
Hint: Did you forget to run `dart run realm_dart install`?
#0      _openRealmLib.throwError (package:realm_dart/src/init.dart:71)
#1      _openRealmLib (package:realm_dart/src/init.dart:97)
#2      initRealm (package:realm_dart/src/init.dart:120)

Flutter app:

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Realm error : Could not open realm_dart. Tried:
- "/Users/kasper/Library/Developer/CoreSimulator/Devices/FB6A66E7-50AF-4C35-8118-83EFE909C4D3/data/Containers/Bundle/Application/80555876-B519-4C9E-A280-5CD535D09A4B/Runner.app/Frameworks/realm_dart.framework/realm_dart"
Hint: Did you forget to add a dependency on the realm package?
#0      _openRealmLib.throwError (package:realm_dart/src/init.dart:71:5)
#1      _openRealmLib (package:realm_dart/src/init.dart:84:29)
#2      initRealm (package:realm_dart/src/init.dart:120:24)
...

[coveralls-official]

Pull Request Test Coverage Report for Build 8536025352

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 10 of 21 (47.62%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.07%) to 86.162%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/realm_dart/lib/src/init.dart	10	21	47.62%

Totals
Change from base Build 8522416033:	-0.07%
Covered Lines:	5834
Relevant Lines:	6771

---

💛 - Coveralls

[elle-j]

Nice with improved error messages 🙂 Just have some small suggestions.