FIX: correctly handle provider edit (#1125)

Prior to this commit, editing the provider wouldn't recompute the provider params. It would also not correctly recompute the "canEditURL" property.

To make possible this commit has:
- made a fix in core: https://github.com/discourse/discourse/pull/31329
- ensures the provider params are recomputed when provider is changed
- made the check on `canEditURL` based on form state and not initial model value

Tests have been added to confirm the expected behavior.

assets/javascripts/discourse/components/ai-llm-editor-form.gjs

@@ -1,7 +1,7 @@
 import Component from "@glimmer/component";
 import { cached, tracked } from "@glimmer/tracking";
 import { concat, fn, get } from "@ember/helper";
-import { action, computed } from "@ember/object";
+import { action } from "@ember/object";
 import { LinkTo } from "@ember/routing";
 import { later } from "@ember/runloop";
 import { service } from "@ember/service";
@@ -37,8 +37,6 @@ export default class AiLlmEditorForm extends Component {
 
       const info = this.args.llms.resultSetMeta.presets.findBy("id", id);
       const modelInfo = info.models.findBy("name", modelName);
-      const params =
-        this.args.llms.resultSetMeta.provider_params[info.provider] ?? {};
 
       return {
         max_prompt_tokens: modelInfo.tokens,
@@ -47,12 +45,7 @@ export default class AiLlmEditorForm extends Component {
         display_name: modelInfo.display_name,
         name: modelInfo.name,
         provider: info.provider,
-        provider_params: Object.fromEntries(
-          Object.entries(params).map(([k, v]) => [
-            k,
-            v?.type === "enum" ? v.default : null,
-          ])
-        ),
+        provider_params: this.computeProviderParams(info.provider),
       };
     }
 
@@ -103,11 +96,6 @@ export default class AiLlmEditorForm extends Component {
     return this.testRunning || this.testResult !== null;
   }
 
-  @computed("args.model.provider")
-  get canEditURL() {
-    return this.args.model.provider !== "aws_bedrock";
-  }
-
   get modulesUsingModel() {
     const usedBy = this.args.model.used_by?.filter((m) => m.type !== "ai_bot");
 
@@ -140,6 +128,21 @@ export default class AiLlmEditorForm extends Component {
     return !this.args.model.isNew;
   }
 
+  computeProviderParams(provider) {
+    const params = this.args.llms.resultSetMeta.provider_params[provider] ?? {};
+    return Object.fromEntries(
+      Object.entries(params).map(([k, v]) => [
+        k,
+        v?.type === "enum" ? v.default : null,
+      ])
+    );
+  }
+
+  @action
+  canEditURL(provider) {
+    return provider !== "aws_bedrock";
+  }
+
   @action
   openAddQuotaModal(addItemToCollection) {
     this.modal.show(AiLlmQuotaModal, {
@@ -220,6 +223,12 @@ export default class AiLlmEditorForm extends Component {
     }
   }
 
+  @action
+  setProvider(provider, { set }) {
+    set("provider_params", this.computeProviderParams(provider));
+    set("provider", provider);
+  }
+
   @action
   delete() {
     return this.dialog.confirm({
@@ -287,6 +296,7 @@ export default class AiLlmEditorForm extends Component {
         @disabled={{this.seeded}}
         @format="large"
         @validation="required"
+        @onSet={{this.setProvider}}
         as |field|
       >
         <field.Select as |select|>
@@ -299,7 +309,7 @@ export default class AiLlmEditorForm extends Component {
       </form.Field>
 
       {{#unless this.seeded}}
-        {{#if this.canEditURL}}
+        {{#if (this.canEditURL data.provider)}}
           <form.Field
             @name="url"
             @title={{i18n "discourse_ai.llms.url"}}

spec/system/llms/ai_llm_spec.rb

@@ -71,6 +71,34 @@ RSpec.describe "Managing LLM configurations", type: :system, js: true do
     expect(llm.user_id).not_to be_nil
   end
 
+  context "when changing the provider" do
+    it "correctly changes the provider params" do
+      visit "/admin/plugins/discourse-ai/ai-llms"
+      find("[data-llm-id='none'] button").click()
+      form.field("provider").select("vllm")
+
+      expect(form).to have_field_with_name("provider_params.disable_system_prompt")
+      expect(form).to have_no_field_with_name("provider_params.disable_native_tools")
+
+      form.field("provider").select("open_router")
+
+      expect(form).to have_field_with_name("provider_params.disable_streaming")
+      expect(form).to have_field_with_name("provider_params.disable_native_tools")
+    end
+
+    it "updates if the url can be edited" do
+      visit "/admin/plugins/discourse-ai/ai-llms"
+      find("[data-llm-id='none'] button").click()
+      form.field("provider").select("vllm")
+
+      expect(form).to have_field_with_name("url")
+
+      form.field("provider").select("aws_bedrock")
+
+      expect(form).to have_no_field_with_name("url")
+    end
+  end
+
   context "with quotas" do
     fab!(:llm_model_1) { Fabricate(:llm_model, name: "claude-2") }
     fab!(:group_1) { Fabricate(:group) }