[v3] Built-in service standardisation and enhancement

[fbbdev]

Description

⚠️ DO NOT MERGE ⚠️

Requires #4045
TODO: update docs
NOTE: this is a synthetic set of commits on top of v3-alpha to facilitate reviews and discussion. The new implementation is built on top of #4045. Clone fbbdev/wails:v3-alpha-feature/service-api for local testing.

This PR drafts some changes meant to standardise and enhance the API of built-in services (fileserver, kvstore, log, sqlite), partly along the lines of the discussions that took place on Discord here and here.

The new API is mostly compatible with the existing one, but has some minor breaking changes.

All services now adhere to the following conventions:

• The service type is called Service for consistent JS imports (fileserver and sqlite used this convention already).
• New() function initialises the service with a sane default configuration (breaking).
• NewWithConfig(config *Config) allows consumers to provide a custom initial configuration.
• Service.Configure(config *Config) allows late configuration and dynamic reconfiguration.
• Service.Configure is never exposed to the frontend, because it could allow arbitrary accesses to the filesystem.
• All methods must be callable concurrently without issue.
• The API must make sense from the Go side as well as from the JS side.

fileserver

• Mostly unchanged
• The default configuration (nil config => no root specified) responds to all requests with 503 Service Unavailable.

kvstore

• Default configuration (nil config => no filename specified) provides an in-memory store. Load and Save methods have no effect.
• New method Service.Load() replaces the current content of the store with those of the associated file.
• Method Service.Save() writes the current content of the store to the associated file.
• New method Service.Clear() empties the store.

On-disk stores are always loaded at startup and saved at shutdown. A clarifying comment has been added to the AutoSave option.

What if one wishes to load from disk, but then keep in-memory only or write to another file? There you go:

// Associate with <file1>
store := kvstore.NewWithConfig(&kvstore.Config{Filename: "<file1>"})

// Load from <file1>
err := store.Load() // handle error

// Reattach to <file2>, this time with autosave
store.Configure(&kvstore.Config{
	Filename: "<file2>",
	AutoSave: true,
})

// Save to <file2>
err := store.Save() // handle error

// Detach from <file2>, becomes in-memory store, loads and saves have no effect
store.Configure(nil)

Notice how Service.Configure changes the configuration but does not alter the state otherwise, i.e. all data is kept, no automatic loads or saves are performed.

log

• Default configuration (nil) writes to application.DefaultLogger(slog.LevelInfo)
• New level type log.Level publishes Debug/Info/Warning/Error constants to JS
• New method Service.Log(ctx context.Context, level Level, message string, args ...any) logs with dynamic level. When called from JS, it receives the binding call context that links to the source window. Custom handlers may access this value.
• New methods Service.DebugContext, Service.InfoContext etc., matching the slog API, accept a context; they are exported to js as Debug, Info etc and receive the binding call context.

The logger implements the slog.Leveler interface to provide dynamic level configuration to custom handlers. See doc comment of the Service.Level method for an example.

sqlite

• Default configuration (nil) creates an in-memory database.
• The database is opened automatically at startup and closed at shutdown.
• Service.Configure method changes the configuration but does not close or reopen the DB.
• Service.Open() opens (if closed) or reopens the DB, applying the latest configuration.
• Service.Close() closes the DB if open; has no effect if closed.
• Service.Select(...) renamed to Service.Query(...) for consistency with sql.DB.
• New methods Service.ExecContext(...) and Service.QueryContext(...) accept a context for cancellation support. These are exported to JS as Exec and Query, hence cancellation is always supported from JS.
• New method Service.Prepare(query string) (cancelable version Service.PrepareContext) creates prepared statements.

Normally statements must be closed manually, but they are closed automatically upon calling Service.Close(). Unlike regular sql.Stmts, their Close method is idempotent.

Advanced binding generator features are used to bring prepared statements to the JS side!

import { Service as sqlite } from "<bindings>/github.com/wailsapp/wails/v3/pkg/services/sqlite";

let stmt = await sqlite.Prepare("SELECT * FROM table WHERE id=?");
let result1 = await stmt.Query("id1");
let result2 = await stmt.Query("id2");
let promise = stmt.Query("id3");
promise.cancel(); // We're having second thoughts.
await promise;
await stmt.Close();

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Ran the services example and verified everything's working fine.

• Windows
• macOS
• Linux

Test Configuration

 Wails (v3.0.0-dev)  Wails Doctor

# System

┌────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
| Name          | MacOS                                                                                                          |
| Version       | 12.6.6                                                                                                         |
| ID            | 21G646                                                                                                         |
| Branding      | Monterey                                                                                                       |
| Platform      | darwin                                                                                                         |
| Architecture  | amd64                                                                                                          |
| Apple Silicon | unknown                                                                                                        |
| CPU           | Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz                                                                       |
| CPU           | Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz                                                                       |
| GPU           |  cores, Metal Family: Supported, Metal GPUFamily macOS 2                                                       |
|       Metal Family: Supported, Metal GPUFamily macOS 2                                                                         |
| Memory        | 32 GB                                                                                                          |
└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

# Build Environment

┌─────────────────────────────────────────────────────────┐
| Wails CLI    | v3.0.0-dev                               |
| Go Version   | go1.23.5                                 |
| Revision     | b88d57cbd960c985bd57bab3e13ead10d1618da9 |
| Modified     | false                                    |
| -buildmode   | exe                                      |
| -compiler    | gc                                       |
| CGO_CFLAGS   |                                          |
| CGO_CPPFLAGS |                                          |
| CGO_CXXFLAGS |                                          |
| CGO_ENABLED  | 1                                        |
| CGO_LDFLAGS  |                                          |
| GOAMD64      | v1                                       |
| GOARCH       | amd64                                    |
| GOOS         | darwin                                   |
| vcs          | git                                      |
| vcs.modified | false                                    |
| vcs.revision | b88d57cbd960c985bd57bab3e13ead10d1618da9 |
| vcs.time     | 2025-02-06T14:05:25Z                     |
└─────────────────────────────────────────────────────────┘

# Dependencies

┌───────────────────────────┐
| Xcode cli tools | 2395    |
| npm             | 10.8.2  |
| *NSIS           | v3.10   |
└─ * - Optional Dependency ─┘

# Checking for issues

 SUCCESS  No issues found

# Diagnosis

 SUCCESS  Your system is ready for Wails development!

Checklist:

• I have updated website/src/pages/changelog.mdx with details of this PR
• My code follows the general coding style of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

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[fbbdev]

Closing in favour of #4067