fix: send empty JSON body on POST requests without a body

[ilyagru]

Problem

When BetterAuthSwift sends a POST request without an explicit body (e.g. signOut()), the request arrives at the better-auth server with an empty body. The server unconditionally calls JSON.parse() on the request body for POST endpoints, and JSON.parse("") throws a SyntaxError, resulting in a 500 Internal Server Error.

Fix

Send {} as the HTTP body for POST requests that have no explicit body set, matching the server's expectation of a valid JSON payload.

} else if self.method == "POST" {
    request.httpBody = Data("{}".utf8)
}

Testing

• Call client.signOut() against a better-auth server — previously returned 500, now returns 200 with { "success": true }.

Fixes #18

Summary by CodeRabbit

Bug Fixes

• Enhanced POST request reliability by automatically providing a valid JSON structure when no request body is specified, ensuring consistent JSON parsing across all request scenarios.

[coderabbitai]

Walkthrough

Adds a fallback to HTTPRequestContext.buildUrlRequest that injects an empty JSON object ({}) as the request body for POST requests that lack a body, preventing server JSON parsing errors during requests like signOut.

Changes

Cohort / File(s)	Summary
Middleware Fallback Sources/Core/Plugins/Middleware.swift	Added POST request body fallback that injects empty JSON object when body is nil, resolving JSON parsing failures on server-side.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A POST without a body, such a lonely request—
Empty JSON whispers, "404—no rest!"
But now a {} arrives, like carrots on a plate,
The server parses happily—signOut works great! 🥕✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately and concisely describes the main change: adding empty JSON body handling for POST requests without a body.
Linked Issues check	✅ Passed	The pull request directly addresses issue #18 by implementing the fix to send empty JSON body on POST requests, resolving the JSON.parse() error and 500 response.
Out of Scope Changes check	✅ Passed	All changes are scoped to the specific problem: adding a fallback for POST requests without a body in HTTPRequestContext.buildUrlRequest.

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[coderabbitai]

🧹 Nitpick comments (1)

Sources/Core/Plugins/Middleware.swift (1)

59-63: LGTM! The fix correctly addresses the server JSON parsing issue.

The implementation properly injects an empty JSON object for POST requests without a body, which resolves the JSON.parse("") error on the server. The comment clearly explains the rationale.

One minor consideration: the method comparison is case-sensitive. While HTTP methods should be uppercase per RFC 7230, and your codebase consistently uses "POST", you could make this slightly more defensive:

💡 Optional: Case-insensitive comparison

-    } else if self.method == "POST" {
+    } else if self.method.uppercased() == "POST" {

This is optional since all your route definitions already use uppercase consistently.

,

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@Sources/Core/Plugins/Middleware.swift` around lines 59 - 63, The POST check
is case-sensitive (self.method == "POST"); make it defensive by comparing
case-insensitively (e.g., normalize self.method via uppercased()/lowercased() or
use a case-insensitive comparison) before setting request.httpBody to
Data("{}".utf8) in Middleware.swift so that the POST branch reliably triggers
regardless of method casing while preserving the existing behavior of injecting
an empty JSON body.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@Sources/Core/Plugins/Middleware.swift`:
- Around line 59-63: The POST check is case-sensitive (self.method == "POST");
make it defensive by comparing case-insensitively (e.g., normalize self.method
via uppercased()/lowercased() or use a case-insensitive comparison) before
setting request.httpBody to Data("{}".utf8) in Middleware.swift so that the POST
branch reliably triggers regardless of method casing while preserving the
existing behavior of injecting an empty JSON body.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 4b7ff8d5-0eca-4262-9d19-ca7bd6059734

📥 Commits

Reviewing files that changed from the base of the PR and between d7bbc6c and ed77ac7.

📒 Files selected for processing (1)

• Sources/Core/Plugins/Middleware.swift

[ouwargui]

thx for the contribution