flutter: Make bindings work

[ethicnology]

Description

This PR attempt to make the flutter bindings work.

Notes to the reviewers

The commits can be individually reviewed but I will develop a bit more here:

• 0db0e0f Removes old generated files that are errored because the original binding doesn't exist anymore
• d1d902d Changes default to new because default is the reserved word in dart which was generating errors.
• 8457a8a Downgrades flutter_rust_bridge from 2.6.0 to 2.0.0, why ? Because the bindings will be unusable with others frb bindings that don't match the same version. For this reason many frb bindings are staying on 2.0.0 (see bdk-flutter, boltz-flutter, or even my package that I had to change for the same reason bip85
• 37a59f5 Set an entrypoint classname, if a user want to create an app with multiple flutter_rust_bridge dependencies it will have to initialize using NostrSdk.init() to avoid conflicts with others flutter_rust_bridge dependencies if they still keep RustLib.init()
• 904797e Regenerates files with previous changes
• 75e579c Exports the generated bindings so they can be called by the developer
• 193cee6 Creates a basic example app that we should make work
• 668551e Comments out some obsolete errored code (facultative)

I'm trying to share my own experience building bip85 bindings using frb.

As I transferred the nostr namespace to you on pub.dev, I also recommend renaming the flutter package nostr instead of nostr_sdk to benefit from visibility.

However the example app doesn't work yet, due to the following error, but it may due to my environement or something I missed in the changes you've implemented in the bindings:

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Invalid argument(s): Failed to load dynamic library 'nostr_sdk_flutter.framework/nostr_sdk_flutter': dlopen(nostr_sdk_flutter.framework/nostr_sdk_flutter, 0x0001): tried: '/Library/Developer/CoreSimulator/Volumes/iOS_22A3351/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 18.0.simruntime/Contents/Resources/RuntimeRootnostr_sdk_flutter.framework/nostr_sdk_flutter' (no such file), '/Users/user/Library/Developer/CoreSimulator/Devices/4662AA9C-CCDA-427E-892A-D3F0F981B7F0/data/Containers/Bundle/Application/3F34743B-2536-4B32-BB63-7A65B4F4F12D/Runner.app/nostr_sdk_flutter.framework/nostr_sdk_flutter' (no such file), '/Library/Developer/CoreSimulator/Volumes/iOS_22A3351/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 18.0.simruntime/Contents/Resources/RuntimeRoot/usr/lib/swift/nostr_sdk_flutter.framework/nostr_sdk_flutter' (no such file), '/usr/lib/swift/nostr_sdk_flutter.framework/nostr_sdk_flutter' (no such file, not in dy<…>
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Checklist

• I followed the contribution guidelines
• I ran just precommit or just check before committing
  –> My changes apply only to dart bindings
• I updated the CHANGELOG (if applicable)
  –> still more work need to be done

[ethicnology]

@yukibtc I would like your opinion on this

[yukibtc]

@yukibtc I would like your opinion on this

Hey, sure. I've to finish a PR and I'll review this

[yukibtc]

Changes looks good.

Regarding the error, I'm unsure about the cause but I was checking if maybe there is some config/dep missing. I noticed that ffigen dependency is not set. I've tried to update (locally) the flutter_rust_bridge.yaml file with this:

rust_input: crate::api
rust_root: rust/
dart_output: lib/src/rust
full_dep: true
c_output: ios/Classes/frb_generated.h 
duplicated_c_output: [macos/Classes/frb_generated.h]

But I receive this error:

--- stderr
  thread 'main' panicked at bindings/nostr-sdk-flutter/rust/build.rs:30:6:
  called `Result::unwrap()` on an `Err` value: ffigen failed. Please refer to https://fzyzcjy.github.io/flutter_rust_bridge/manual/ffigen-troubleshooting for details

I followed the troubleshooting guide but still not works.

[yukibtc]

I see, in general, that the pubspec.yaml have many differences with your or the BDK/Boltz ones. Miss some deps and this section is different:

flutter:
  plugin:
    platforms:
      android:
        package: org.rustnostr.nostr_sdk
        pluginClass: NostrSdkPlugin
      ios:
        pluginClass: NostrSdkPlugin
      linux:
        pluginClass: NostrSdkPlugin
      macos:
        pluginClass: NostrSdkPlugin
      windows:
        pluginClass: NostrSdkPluginCApi

I think it should be replaced with:

flutter:
  plugin:
    platforms:
      android:
        ffiPlugin: true
      ios:
        ffiPlugin: true
      linux:
        ffiPlugin: true
      macos:
        ffiPlugin: true
      windows:
        ffiPlugin: true

I don't remember how I generated the flutter packet. Maybe I generated it incorrectly (not for bindings).

[yukibtc]

I've completely recreated the package and cherry picked your changes. It still return the "Failed to load dynamic library..." error. I think because the rust library name is different from the flutter one: I tried to generate a new package, add the rust code and run the example and works. But when I change the flutter name (or the rust lib name) it no longer works (not find the library, also if I update all the names across the code). I'll try to look for a solution

[yukibtc]

@ethicnology I've moved the bindings to https://github.com/rust-nostr/nostr-sdk-flutter

Now the example works (run with just example).

I tried to rename it to nostr but it create conflicts because there is already a rust crate named nostr in the Cargo.lock. I tried to rename only the flutter package and not the rust one but then it fail to load the library

[ethicnology]

@yukibtc

I had the same problem with bip85, I ended up re-creating a project with the proper name (bip85) and rename the rust crates (bip85_extended)

I've also changed the import method in the example using github rather than the relative path