From 39b17ddd3064cd777ddbcca4063455a2ee2bc31b Mon Sep 17 00:00:00 2001
From: "fogtype.com" <noreply@tangled.sh>
Date: Thu, 17 Apr 2025 15:28:17 +0000
Subject: [PATCH] Fix atom feed link construction
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This pull request introduces a helper function `newAtomLink` to correctly construct Atom feed links using subdomains and slugs. Previously, the feed link was generated using `filepath.Join`, which is intended for file paths and caused malformed URLs like:

```
https://example.comfoo/bar
```

Now, the link is properly constructed in the format:

```
https://<subdomain>.<host>/<slug>
```

Example:

```go
newAtomLink("https://example.com", "blog", "some-post")
// → <link href="https://blog.example.com/some-post"></link>
```

This change improves the correctness and clarity of Atom feed generation by replacing inappropriate path logic with URL-aware composition via url.Parse.
---
 atom/feed.go | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/atom/feed.go b/atom/feed.go
index 73e8470..85a6506 100644
--- a/atom/feed.go
+++ b/atom/feed.go
@@ -3,6 +3,7 @@ package atom
 import (
 	"encoding/xml"
 	"fmt"
+	"net/url"
 	"path/filepath"
 	"time"
 
@@ -80,8 +81,7 @@ func NewAtomFeed(srcDir string, posts []types.Post) ([]byte, error) {
 				dateStr,
 				filepath.Join(srcDir, p.Meta["slug"].(string)),
 			),
-			// filepath.Join strips the second / in http://
-			Link: &AtomLink{Href: config.Config.URL + filepath.Join(srcDir, p.Meta["slug"].(string))},
+			Link: newAtomLink(config.Config.URL, srcDir, p.Meta["slug"].(string)),
 			Summary: &AtomSummary{
 				Content: summaryContent,
 				Type:    "html",
@@ -113,3 +113,21 @@ func NewAtomFeed(srcDir string, posts []types.Post) ([]byte, error) {
 	// Add the <?xml...> header.
 	return []byte(xml.Header + string(feedXML)), nil
 }
+
+// Creates a new Atom link.
+//
+// Example:
+//
+//	newAtomLink("https://example.com", "blog", "some-post")
+//	// → <link href="https://blog.example.com/some-post"></link>
+func newAtomLink(base string, subdomain string, slug string) *AtomLink {
+	baseURL, err := url.Parse(base)
+	if err != nil {
+		return nil
+	}
+
+	baseURL.Host = subdomain + "." + baseURL.Host
+	baseURL.Path = slug
+
+	return &AtomLink{Href: baseURL.String()}
+}
-- 
2.51.2