Plugins can declare dependencies on other plugins. The dependency resolver uses topological sort to determine activation order.

{
  "dependencies": [
    {
      "id": "xbot.utils",
      "version": "^1.0.0"
    }
  ]
}

The DependencyResolver (plugin/dependency.go) uses Kahn’s algorithm (BFS-based topological sort) with O(V+E) time complexity.

type DependencyResolver struct { ... }

func NewDependencyResolver() *DependencyResolver
func (dr *DependencyResolver) AddManifest(m *PluginManifest)
func (dr *DependencyResolver) Resolve() ([]string, error)
func (dr *DependencyResolver) Validate() error

Returns the activation order — plugins with no dependencies come first, followed by plugins that depend on them:

dr := NewDependencyResolver()
dr.AddManifest(manifestA)  // no deps
dr.AddManifest(manifestB)  // depends on A
dr.AddManifest(manifestC)  // depends on A and B

order, err := dr.Resolve()
// order = ["xbot.a", "xbot.b", "xbot.c"]

Checks that all declared dependencies exist among the added manifests. Returns ErrMissingDependency for the first missing dependency.

type ErrMissingDependency struct {
    PluginID string  // Plugin that has the missing dependency
    Missing  string  // Missing dependency ID
}

Returned when a plugin declares a dependency on a plugin that doesn’t exist.

type ErrCircularDependency struct {
    Cycle []string  // Plugin IDs in the cycle
}

Returned when a circular dependency is detected. The Cycle field lists the plugins involved in the cycle.

Version constraints use semver range syntax:

Note: Currently only format validation is performed. Actual version resolution will be added in a future iteration.

During PluginManager.Discover(), after all manifests are loaded:

1. All manifests are added to the DependencyResolver
2. Resolve() is called to get the activation order
3. ActivateAll() activates plugins in dependency order
4. If resolution fails (missing dependency or cycle), an error is logged but discovery continues — plugins are still loaded without guaranteed order

// plugin.json for "xbot.utils"
{
  "id": "xbot.utils",
  "name": "Utils",
  "version": "1.0.0",
  "runtime": "native",
  "entry": ""
}

// plugin.json for "xbot.my-plugin"
{
  "id": "xbot.my-plugin",
  "name": "My Plugin",
  "version": "1.0.0",
  "runtime": "stdio",
  "entry": "python3 main.py",
  "dependencies": [
    {"id": "xbot.utils", "version": "^1.0.0"}
  ]
}

xbot.utils activates before xbot.my-plugin.

• Plugin Manifest — Where dependencies are declared
• Architecture — How dependencies affect activation
• API Reference — DependencyResolver API