fix(tool-cordis): pass primitive provided service values through the façade

cordis provide() accepts any value and cross-mount composition advertises
ctx.provide('name', value), but the façade's readService unconditionally
proxied every declared service — new Proxy('42') throws "Cannot create proxy
with a non-object as target or handler", so a consumer of a primitive-valued
service crashed on first read with an error naming neither the service nor
the fix. A primitive or null value now passes through unwrapped (after the
denyContext check); only object- and function-valued services are proxied —
a primitive has no method that could hand back a Context, so nothing is lost.
New cross-mount spec pins both read paths (ctx.<name> and ctx.get) for a
number and a null provided value.

packages/cordis/tool-cordis/src/guard.ts

@@ -9,8 +9,9 @@
  * The façade is a WHITELIST, not a pass-through proxy. Mount code needs to do
  * exactly four things — register a tool, listen to an event, provide a service,
  * call an injected service (timers included) — so the façade exposes only those
- * verbs and the injected services, each individually wrapped. Every framework
+ * verbs and the injected services, each object-valued service individually
- * plumbing member (`root`, `parent`, `scope`, `fiber`, `reflect`, `registry`,
+ * wrapped (a primitive provided value passes through as-is — see
+ * {@link sandboxContext}). Every framework plumbing member (`root`, `parent`, `scope`, `fiber`, `reflect`, `registry`,
  * `events`, `extend`, `isolate`, `intercept`, `plugin`, `set`, `mixin`, …) is
  * DENIED with a teaching error rather than passed through. This closes an
  * entire escape class at once: a pass-through proxy that only special-cased
@@ -284,11 +285,17 @@ function sandboxContext(ctx: Context): Context {
   // error; a DECLARED one resolves to the guarded service. A declared inject
   // is required in cordis (the fiber only activates once every declared
   // service is live), so at `apply`/`execute` time `ctx.get(name)` is present
-  // for a declared name — no undefined case to handle here.
+  // for a declared name — no undefined case to handle here. `provide()`
+  // accepts ANY value though (cross-mount composition advertises
+  // `ctx.provide('name', value)`), so a primitive or null value passes
+  // through unwrapped: Proxy throws on a non-object target, and only an
+  // object can carry a method that hands back a Context.
   const readService = (name: string): unknown => {
     if (name === 'tools') return tools
     if (!declared.has(name)) return denyRead(name)
-    return guardedService(ctx.get(name) as object, name)
+    const service = denyContext(ctx.get(name), name)
+    if (service === null || (typeof service !== 'object' && typeof service !== 'function')) return service
+    return guardedService(service, name)
   }
   const get = (name: string): unknown => readService(name)
   return new Proxy({}, {

packages/cordis/tool-cordis/tests/cross-mount.spec.ts

@@ -91,6 +91,44 @@ describe('cross-mount provide/inject', () => {
     expect(api).toContain('- greeter (provided by greeter-provider, no catalog entry)')
   })
 
+  it('a primitive (or null) provided value passes through the façade unwrapped, on both read paths', async () => {
+    const ctx = await setup()
+    const provider = await call(ctx, 'cordis_mount', {
+      code: `
+        return {
+          name: 'answer-provider',
+          apply(ctx) {
+            ctx.provide('answer', 42)
+            ctx.provide('nothing', null)
+          },
+        }
+      `,
+    })
+    expect(provider.isError).toBe(false)
+
+    const consumer = await call(ctx, 'cordis_mount', {
+      code: `
+        return {
+          name: 'answer-consumer',
+          inject: ['answer', 'nothing', 'tools'],
+          apply(ctx) {
+            harness.registerTool(ctx, harness.defineTool({
+              name: 'answer',
+              description: 'Read the provided primitive services.',
+              parameters: {},
+              async execute() {
+                return [{ type: 'text', text: ctx.answer + '/' + ctx.get('answer') + '/' + ctx.nothing }]
+              },
+            }))
+          },
+        }
+      `,
+    })
+    expect(consumer.isError).toBe(false)
+    expect(text(consumer)).toContain('state: active')
+    expect(text(await call(ctx, 'answer', {}))).toBe('42/42/null')
+  })
+
   it('unmounting the consumer leaves the provider and its service intact', async () => {
     const ctx = await setup()
     await call(ctx, 'cordis_mount', { code: PROVIDER_CODE })   // dyn-1