feat: add docs to metadata (#135)

common/codec.ts

@@ -92,11 +92,20 @@ export abstract class Codec<T> {
     }
     try {
       codecInspectCtx.set(this, null)
-      const metadata = this._metadata[0]
-      if (!metadata) return "?"
-      const content = metadata.type === "atomic"
-        ? metadata.name
-        : `${metadata.name}(${inspect(metadata.args).replace(/^\[(?: (.+) |(.+))\]$/s, "$1$2")})`
+      let content = ""
+      for (const metadata of this._metadata) {
+        if (metadata.type === "docs") {
+          // TODO: print docs in inspect
+        } else {
+          if (metadata.type === "atomic") {
+            content += metadata.name
+          } else if (metadata.type === "factory") {
+            content += `${metadata.name}(${inspect(metadata.args).replace(/^\[(?: (.+) |(.+))\]$/s, "$1$2")})`
+          }
+          break
+        }
+      }
+      content ||= "?"
       id = codecInspectCtx.get(this)
       return id !== null ? `$${id} = ${content}` : content
     } finally {

common/metadata.ts

@@ -4,15 +4,23 @@ export type Metadata<T> = Array<
   | {
     type: "atomic"
     name: string
+    docs?: never
     factory?: never
     args?: never
   }
   | {
     type: "factory"
     name: string
+    docs?: never
     factory: (...args: any) => Codec<T>
     args: any[]
   }
+  | {
+    type: "docs"
+    docs: string
+    factory?: never
+    args?: never
+  }
 >
 
 /** Metadata for an atomic codec */
@@ -51,6 +59,10 @@ export function metadata<T>(
   ]
 }
 
+export function docs<T = any>(docs: string): Metadata<T> {
+  return [{ type: "docs", docs }]
+}
+
 export class CodecVisitor<R> {
   #fallback?: <T>(codec: Codec<T>) => R
   #visitors = new Map<Codec<any> | Function, (codec: Codec<any>, ...args: any[]) => R>()
@@ -91,7 +103,7 @@ export class CodecVisitor<R> {
     const visitor = this.#visitors.get(codec)
     if (visitor) return visitor(codec)
     for (const metadata of codec._metadata) {
-      if (metadata.type === "atomic") continue
+      if (metadata.type !== "factory") continue
       const visitor = this.#visitors.get(metadata.factory)
       if (visitor) return visitor(codec, ...metadata.args)
     }