Refactor baseUrl handling in LangflowClient constructor and add tests for missing baseUrl scenarios

If baseUrl is provided as an property on the opts, but is it undefined or null, this is likely not the intention. Previously the baseUrl would get set to the DATASTAX_LANGFLOW_BASE_URL and the instantiation would fail due to a missing langflowId. Now it will throw an more useful error, unless langflowId and apiKey are present.

Author: philnash

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Ongoing [☰](https://github.com/datastax/langflow-client-ts/compare/v0.2.1...main)
 
+### Changed
+
+- When you explicitly try to set the `baseUrl` for a client, but it is undefined, null or empty, it now throws an error with a better explanation.
+
 ## 0.3.0 (May 30, 2025) [☰](https://github.com/datastax/langflow-client-ts/compare/v0.2.1...v0.3.0)
 
 ### Added

src/index.ts

@@ -34,7 +34,7 @@ export class LangflowClient {
   logs: Logs;
 
   constructor(opts: LangflowClientOptions) {
-    this.baseUrl = opts.baseUrl ?? DATASTAX_LANGFLOW_BASE_URL;
+    this.baseUrl = this.#resolveBaseUrl(opts);
     this.basePath = "/api";
     this.langflowId = opts.langflowId;
     this.apiKey = opts.apiKey;
@@ -63,6 +63,35 @@ export class LangflowClient {
     this.logs = new Logs(this);
   }
 
+  #resolveBaseUrl(opts: LangflowClientOptions) {
+    // If baseUrl is provided as an property on the opts, but is it undefined or
+    // null, this is likely not the intention.
+    // Previously the baseUrl would get set to the DATASTAX_LANGFLOW_BASE_URL
+    // and the instantiation would fail due to a missing langflowId. Now it will
+    // throw an more useful error, unless langflowId and apiKey are present.
+    if (Object.hasOwn(opts, "baseUrl")) {
+      const isBaseUrlEffectivelyEmpty =
+        typeof opts.baseUrl === "undefined" ||
+        opts.baseUrl === null ||
+        (typeof opts.baseUrl === "string" && opts.baseUrl.trim() === "");
+
+      if (isBaseUrlEffectivelyEmpty) {
+        // BaseUrl is explicitly provided but is empty/undefined/null.
+        // If langflowId and apiKey are also provided, assume DataStax
+        // connection and use the default DataStax URL.
+        if (opts.langflowId && opts.apiKey) {
+          return DATASTAX_LANGFLOW_BASE_URL;
+        }
+        // Otherwise, this is an invalid configuration.
+        throw new TypeError(
+          `You are trying to set baseUrl, but the value is '${String(opts.baseUrl)}'.`
+        );
+      }
+      // If opts.baseUrl is explicitly set and not effectively empty, it will be used by the return statement below.
+    }
+    return opts.baseUrl ?? DATASTAX_LANGFLOW_BASE_URL;
+  }
+
   #isDataStax(): boolean {
     return this.baseUrl === DATASTAX_LANGFLOW_BASE_URL;
   }

src/test/index.test.ts

@@ -542,4 +542,53 @@ describe("LangflowClient", () => {
       });
     });
   });
+
+  describe("with a missing baseUrl", () => {
+    const apiKey = "my-api-key";
+    const langflowId = "my-langflow-id";
+
+    [undefined, ""].forEach((baseUrl) => {
+      it(`throws an error baseUrl is set to '${String(baseUrl)}'`, () => {
+        try {
+          new LangflowClient({ baseUrl });
+        } catch (error) {
+          assert.ok(error instanceof TypeError);
+          assert.match(
+            error.message,
+            /You are trying to set baseUrl, but the value is/
+          );
+        }
+      });
+
+      it(`throws an error when baseUrl is set to '${String(baseUrl)}' and only langflowId is provided`, () => {
+        try {
+          new LangflowClient({ baseUrl, langflowId });
+        } catch (error) {
+          assert.ok(error instanceof TypeError);
+          assert.match(
+            error.message,
+            /You are trying to set baseUrl, but the value is/
+          );
+        }
+      });
+
+      it(`throws an error when baseUrl is set to '${String(baseUrl)}' and only apiKey is provided`, () => {
+        try {
+          new LangflowClient({ baseUrl, apiKey });
+        } catch (error) {
+          assert.ok(error instanceof TypeError);
+          assert.match(
+            error.message,
+            /You are trying to set baseUrl, but the value is/
+          );
+        }
+      });
+
+      it(`doesn't throw when baseUrl is set to '${String(baseUrl)}' and langflowId and apiKey are provided`, () => {
+        assert.doesNotThrow(() => {
+          new LangflowClient({ baseUrl, apiKey, langflowId });
+        });
+      });
+    });
+  });
 });