From ce9a467a05739cd126396bddf5f935cce69bb74c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Magnus=20Gro=C3=9F?= <magnus@mggross.com>
Date: Thu, 6 Apr 2023 08:40:16 +0200
Subject: [PATCH] Return empty list on invalid globs

Regression was introduced in 9479c2801093d856811fda3660e50fb8be9d3f5c.

Since that commit, providing an invalid glob to tera will make it fail
to create an instance, first (in that commit) by making it panic and
since 1f958784b8be7d8ccba443a19c1417f8ff48b329 by making it return an
error.

While returning an error is not entirely unlogical, it doesn't match
what most languages do with invalid globs.

- Bash will by default return an empty set on invalid globs, as the
  `failglob` option is off by default
- Python will likewise return the empty set instead of throwing an
  exception, when doing something like `glob.glob("/dev/null/*")`
- Rust's `globwalk` will also not error, but return an empty set

In fact, we use globwalk in tera and the only reason we panic is by
accident, because `std::fs::canonicalize()` checks the path.

It is better to match other language's glob behaviour, therefore we
resort back to the original path if `canonicalize()` fails.

We should especially restore the previous behaviour, as this caused a
lot of regressions already, including in zola.

Fixes https://github.com/getzola/zola/issues/2150

ref: #819
ref: #820
ref: #799
---
 src/tera.rs | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/tera.rs b/src/tera.rs
index bf29f6d8..81f9057b 100644
--- a/src/tera.rs
+++ b/src/tera.rs
@@ -132,7 +132,13 @@ impl Tera {
         // See https://github.com/Keats/tera/issues/574 for the Tera discussion
         // and https://github.com/Gilnaa/globwalk/issues/28 for the upstream issue.
         let (parent_dir, glob_end) = glob.split_at(glob.find('*').unwrap());
-        let parent_dir = std::fs::canonicalize(parent_dir)?;
+        let parent_dir = match std::fs::canonicalize(parent_dir) {
+            Ok(d) => d,
+            // If canonicalize fails, just abort it and resume with the given path.
+            // Consumers expect invalid globs to just return the empty set instead of failing.
+            // See https://github.com/Keats/tera/issues/819#issuecomment-1480392230
+            Err(_) => std::path::PathBuf::from(parent_dir),
+        };
         let dir = parent_dir.join(glob_end).into_os_string().into_string().unwrap();
 
         // We are parsing all the templates on instantiation
@@ -1222,9 +1228,10 @@ mod tests {
 
     // https://github.com/Keats/tera/issues/819
     #[test]
-    fn doesnt_panic_on_invalid_glob() {
+    fn empty_list_on_invalid_glob() {
         let tera = Tera::new("\\dev/null/*");
         println!("{:?}", tera);
-        assert!(tera.is_err());
+        assert!(tera.is_ok());
+        assert!(tera.unwrap().templates.is_empty());
     }
 }