Migrate web core to signals

renderers/web_core/package.json

@@ -92,7 +92,7 @@
     "zod-to-json-schema": "^3.25.1"
   },
   "dependencies": {
-    "rxjs": "^7.8.2",
+    "@preact/signals-core": "^1.13.0",
     "zod": "^3.25.76"
   }
-}
+}

renderers/web_core/src/v0_9/basic_catalog/functions/basic_functions.test.ts

@@ -16,6 +16,7 @@
 
 import { describe, it } from "node:test";
 import * as assert from "node:assert";
+import { effect } from "@preact/signals-core";
 import { BASIC_FUNCTIONS } from "./basic_functions.js";
 import { DataModel } from "../../state/data-model.js";
 import { DataContext } from "../../rendering/data-context.js";
@@ -238,11 +239,16 @@ describe("BASIC_FUNCTIONS", () => {
       const result = BASIC_FUNCTIONS.formatString(
         { value: "hello world" },
         context,
-      ) as import("rxjs").Observable<string>;
+      ) as import("@preact/signals-core").Signal<string>;
 
-      result.subscribe((val) => {
-        assert.strictEqual(val, "hello world");
-        done();
+      let cleanup: (() => void) | undefined;
+      cleanup = effect(() => {
+        const val = result.value;
+        if (val) {
+          assert.strictEqual(val, "hello world");
+          if (cleanup) cleanup();
+          done();
+        }
       });
     });
 
@@ -251,32 +257,30 @@ describe("BASIC_FUNCTIONS", () => {
       const result = BASIC_FUNCTIONS.formatString(
         { value: "Value: ${a}" },
         context,
-      ) as import("rxjs").Observable<string>;
+      ) as import("@preact/signals-core").Signal<string>;
 
       let emitCount = 0;
-      const sub = result.subscribe({
-        next: (val) => {
-          try {
-            if (emitCount === 0) {
-              assert.strictEqual(val, "Value: 10");
-              emitCount++;
-              // Trigger a change in the next tick to avoid uninitialized sub
-              setTimeout(() => {
-                dataModel.set("/a", 42);
-              }, 0);
-            } else if (emitCount === 1) {
-              assert.strictEqual(val, "Value: 42");
-              emitCount++;
-              sub.unsubscribe();
-              done();
-            }
-          } catch (e) {
-            done(e);
+      let cleanup: (() => void) | undefined;
+      cleanup = effect(() => {
+        const val = result.value;
+        try {
+          if (emitCount === 0) {
+            assert.strictEqual(val, "Value: 10");
+            emitCount++;
+            // Trigger a change in the next tick to avoid uninitialized sub
+            setTimeout(() => {
+              dataModel.set("/a", 42);
+            }, 0);
+          } else if (emitCount === 1) {
+            assert.strictEqual(val, "Value: 42");
+            emitCount++;
+            if (cleanup) cleanup();
+            done();
           }
-        },
-        error: (e) => {
+        } catch (e) {
+          if (cleanup) cleanup();
           done(e);
-        },
+        }
       });
     });
 
@@ -292,11 +296,16 @@ describe("BASIC_FUNCTIONS", () => {
       const result = BASIC_FUNCTIONS.formatString(
         { value: "Result: ${add(a: 5, b: 7)}" },
         ctxWithInvoker,
-      ) as import("rxjs").Observable<string>;
+      ) as import("@preact/signals-core").Signal<string>;
 
-      result.subscribe((val) => {
-        assert.strictEqual(val, "Result: 12");
-        done();
+      let cleanup: (() => void) | undefined;
+      cleanup = effect(() => {
+        const val = result.value;
+        if (val) {
+          assert.strictEqual(val, "Result: 12");
+          if (cleanup) cleanup();
+          done();
+        }
       });
     });
 

renderers/web_core/src/v0_9/basic_catalog/functions/basic_functions.ts

@@ -15,8 +15,7 @@
  */
 
 import { ExpressionParser } from "../expressions/expression_parser.js";
-import { Observable, combineLatest, of } from "rxjs";
-import { map } from "rxjs/operators";
+import { computed, Signal } from "@preact/signals-core";
 import { FunctionImplementation } from "../../catalog/types.js";
 
 /**
@@ -156,27 +155,24 @@ export const BASIC_FUNCTIONS: Record<string, FunctionImplementation> = {
 
     if (parts.length === 0) return "";
 
-    const observables = parts.map((part) => {
-      // If it's a literal string (or number/boolean/etc), wrap it in 'of'
+    const dynamicParts = parts.map((part) => {
+      // If it's a literal string (or number/boolean/etc), keep it as is
       if (typeof part !== "object" || part === null || Array.isArray(part)) {
-        return of(part);
+        return part;
       }
-
-      // Otherwise, it's a dynamic value we need to subscribe to
-      return new Observable<unknown>((subscriber) => {
-        const sub = context.subscribeDynamicValue(part, (val) => {
-          subscriber.next(val);
-        });
-
-        // Emit the initial synchronously-resolved value
-        subscriber.next(sub.value);
-
-        return () => sub.unsubscribe();
-      });
+      return context.resolveSignal(part);
     });
 
-    // Combine all parts and join them into a single string whenever any part changes
-    return combineLatest(observables).pipe(map((values) => values.join("")));
+    return computed(() => {
+      return dynamicParts
+        .map((p) => {
+          if (p instanceof Signal) {
+             return p.value;
+          }
+          return p;
+        })
+        .join("");
+    });
   },
 
   /**

renderers/web_core/src/v0_9/catalog/types.ts

@@ -16,15 +16,15 @@
 
 import { z } from "zod";
 import { DataContext } from "../rendering/data-context.js";
-import { Observable } from "rxjs";
+import { Signal } from "@preact/signals-core";
 
 /**
  * A function implementation that can be registered with the evaluator or basic catalog.
  */
 export type FunctionImplementation = (
   args: Record<string, unknown>,
   context: DataContext,
-) => unknown | Observable<unknown>;
+) => unknown | Signal<unknown>;
 
 /**
  * A definition of a UI component's API.

renderers/web_core/src/v0_9/rendering/data-context.test.ts

@@ -16,7 +16,7 @@
 
 import assert from "node:assert";
 import { describe, it, beforeEach } from "node:test";
-import { of } from "rxjs";
+import { signal } from "@preact/signals-core";
 import { DataModel } from "../state/data-model.js";
 import { DataContext } from "./data-context.js";
 
@@ -172,7 +172,7 @@ describe("DataContext", () => {
 
   it("subscribes to function call returning an observable", () => {
     const fnInvoker = (name: string) => {
-      if (name === "obs") return of("hello");
+      if (name === "obs") return signal("hello");
       return null;
     };
     const ctx = new DataContext(model, "/", fnInvoker);