refactor: resend client options

[Shubhdeep12]

• updated the resend constructor to accept optional client options for base URL, user agent and custom fetch.
• added a new type -> ResendClientOptions.
• updated tests

---

Summary by cubic

Add support for per-client options in the Resend constructor (baseUrl, userAgent, custom fetch) to improve configurability and testing. Client options now take precedence over env vars and allow explicit empty values.

• New Features
  • New ResendClientOptions type; exported from resend and index.
  • fetchRequest uses instance baseUrl and fetch; tests assert fetch URLs and client-option error paths.

^{Written for commit 38ba8fc. Summary will update on new commits.}

[pkg-pr-new]

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npm i https://pkg.pr.new/resend@865

commit: e8039ba

[cubic-dev-ai]

3 issues found across 4 files

Confidence score: 3/5

• There is a concrete behavior risk in src/resend.ts: using baseUrl ?? default means an empty-string env/config value is treated as valid, which can produce relative request URLs instead of using the intended API host.
• This lands in moderate-risk territory because the top issue is medium severity (6/10) with high confidence (9/10) and can affect real request routing at runtime.
• The tests in src/broadcasts/broadcasts.spec.ts and src/emails/emails.spec.ts are currently weak on URL assertions, so they may pass even when baseUrl handling is broken, reducing safety against regressions.
• Pay close attention to src/resend.ts, src/broadcasts/broadcasts.spec.ts, and src/emails/emails.spec.ts - fix empty-string baseUrl fallback behavior and add explicit request-URL assertions.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/broadcasts/broadcasts.spec.ts">

<violation number="1" location="src/broadcasts/broadcasts.spec.ts:286">
P2: Client-options fetch-failure test is non-diagnostic because it relies on globally mocked fetch without asserting the request URL, so it may pass even if `baseUrl` is ignored.</violation>
</file>

<file name="src/resend.ts">

<violation number="1" location="src/resend.ts:66">
P2: Using nullish coalescing for `baseUrl` allows empty-string config/env values, causing relative request URLs instead of falling back to the default API host.</violation>
</file>

<file name="src/emails/emails.spec.ts">

<violation number="1" location="src/emails/emails.spec.ts:410">
P2: Client-options test does not verify `baseUrl` usage, so it can pass without proving the option is honored.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

1 issue found across 3 files (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/resend.ts">

<violation number="1" location="src/resend.ts:66">
P2: Using `||` instead of `??` for client option precedence causes explicit empty-string overrides to be ignored, introducing a behavioral regression.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

1 issue found across 1 file (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/resend.ts">

<violation number="1" location="src/resend.ts:66">
P2: Using `??` for `baseUrl`/`userAgent` allows empty strings to bypass defaults, causing invalid or unintended request targets instead of safe fallback.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

P2: Using ?? for baseUrl/userAgent allows empty strings to bypass defaults, causing invalid or unintended request targets instead of safe fallback.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At src/resend.ts, line 66:

<comment>Using `??` for `baseUrl`/`userAgent` allows empty strings to bypass defaults, causing invalid or unintended request targets instead of safe fallback.</comment>

<file context>
@@ -63,9 +63,9 @@ export class Resend {
 
     this.baseUrl =
-      options?.baseUrl || getEnv('RESEND_BASE_URL') || defaultBaseUrl;
+      options?.baseUrl ?? (getEnv('RESEND_BASE_URL') || defaultBaseUrl);
     const userAgent =
-      options?.userAgent || getEnv('RESEND_USER_AGENT') || defaultUserAgent;
</file context>