fix(ui): omit optional scalar defaults from JsonSchemaForm so empty number fields don't submit as 0 (PAPA-407)

getDefaultForSchema previously materialised a value of 0 for any number
field without an explicit default (and "" for any optional string),
which is what `getDefaultValues` then seeded the form with. That meant
the exe.dev environment form opened with `cpu: 0` baked in even though
the user never touched the field, and submitting the form failed
server-side validation:

  "cpu must be greater than 0 when provided."

Fix: only materialise scalar (string / number / integer / secret-ref)
defaults when the schema actually declares one. Booleans, enums, arrays
and objects still get sensible empty values so checkbox/array UI keeps
working. Object recursion now skips properties whose defaults resolve
to undefined so they stay out of the submitted payload.

Adds a regression test that getDefaultValues omits optional scalars
without an explicit default while still honouring fields that do
declare one.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/components/JsonSchemaForm.test.tsx

@@ -3,7 +3,7 @@
 import { act } from "react";
 import { createRoot } from "react-dom/client";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
-import { JsonSchemaForm } from "./JsonSchemaForm";
+import { JsonSchemaForm, getDefaultValues } from "./JsonSchemaForm";
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 (globalThis as any).IS_REACT_ACT_ENVIRONMENT = true;
@@ -350,6 +350,31 @@ describe("JsonSchemaForm secret-ref rendering", () => {
     });
   });
 
+  it("omits optional scalar fields from getDefaultValues so empty inputs aren't submitted as 0/''", () => {
+    const defaults = getDefaultValues({
+      type: "object",
+      properties: {
+        apiKey: { type: "string", format: "secret-ref" },
+        sshPort: { type: "number", default: 22 },
+        cpu: { type: "number" },
+        memory: { type: "string" },
+        reuseLease: { type: "boolean", default: false },
+        tags: { type: "array", items: { type: "string" } },
+      },
+    });
+
+    // Fields with explicit defaults round-trip.
+    expect(defaults.sshPort).toBe(22);
+    expect(defaults.reuseLease).toBe(false);
+    expect(defaults.tags).toEqual([]);
+
+    // Optional scalars without explicit defaults stay out of the payload so
+    // the server doesn't see e.g. `cpu: 0` and reject the submission.
+    expect("apiKey" in defaults).toBe(false);
+    expect("cpu" in defaults).toBe(false);
+    expect("memory" in defaults).toBe(false);
+  });
+
   it("keeps the password fallback for short raw values", async () => {
     const root = createRoot(container);
 

ui/src/components/JsonSchemaForm.tsx

@@ -134,7 +134,14 @@ export function labelFromKey(key: string, schema: JsonSchemaNode): string {
     .replace(/\b\w/g, (c) => c.toUpperCase());
 }
 
-/** Produce a sensible default value for a schema node. */
+/**
+ * Produce a sensible default value for a schema node.
+ *
+ * Optional scalar fields (string, number, integer, secret-ref) without an
+ * explicit `default` return `undefined` so they stay out of the submitted
+ * payload — otherwise an empty field would round-trip as `""` or `0` and
+ * trip server-side "X must be greater than 0 when provided" style validators.
+ */
 export function getDefaultForSchema(schema: JsonSchemaNode): unknown {
   if (schema.default !== undefined) return schema.default;
 
@@ -142,10 +149,9 @@ export function getDefaultForSchema(schema: JsonSchemaNode): unknown {
   switch (type) {
     case "string":
     case "secret-ref":
-      return "";
     case "number":
     case "integer":
-      return schema.minimum ?? 0;
+      return undefined;
     case "boolean":
       return false;
     case "enum":
@@ -156,12 +162,13 @@ export function getDefaultForSchema(schema: JsonSchemaNode): unknown {
       if (!schema.properties) return {};
       const obj: Record<string, unknown> = {};
       for (const [key, propSchema] of Object.entries(schema.properties)) {
-        obj[key] = getDefaultForSchema(propSchema);
+        const def = getDefaultForSchema(propSchema);
+        if (def !== undefined) obj[key] = def;
       }
       return obj;
     }
     default:
-      return "";
+      return undefined;
   }
 }