Fix logic for checking if a compute can install a remote extension (#10656)

Given a remote extensions manifest of the following:

```json
  {
    "public_extensions": [],
    "custom_extensions": null,
    "library_index": {
      "pg_search": "pg_search"
    },
    "extension_data": {
      "pg_search": {
        "control_data": {
          "pg_search.control": "comment = 'pg_search: Full text search for PostgreSQL using BM25'\ndefault_version = '0.14.1'\nmodule_pathname = '$libdir/pg_search'\nrelocatable = false\nsuperuser = true\nschema = paradedb\ntrusted = true\n"
        },
        "archive_path": "13117844657/v14/extensions/pg_search.tar.zst"
      }
    }
  }
```

We were allowing a compute to install a remote extension that wasn't
listed in either public_extensions or custom_extensions.

Signed-off-by: Tristan Partin <tristan@neon.tech>

libs/compute_api/src/spec.rs

@@ -204,14 +204,16 @@ impl RemoteExtSpec {
 
         // Check if extension is present in public or custom.
         // If not, then it is not allowed to be used by this compute.
-        if let Some(public_extensions) = &self.public_extensions {
+        if !self
-            if !public_extensions.contains(&real_ext_name.to_string()) {
+            .public_extensions
-                if let Some(custom_extensions) = &self.custom_extensions {
+            .as_ref()
-                    if !custom_extensions.contains(&real_ext_name.to_string()) {
+            .is_some_and(|exts| exts.iter().any(|e| e == ext_name))
-                        return Err(anyhow::anyhow!("extension {} is not found", real_ext_name));
+            && !self
-                    }
+                .custom_extensions
-                }
+                .as_ref()
-            }
+                .is_some_and(|exts| exts.iter().any(|e| e == ext_name))
+        {
+            return Err(anyhow::anyhow!("extension {} is not found", real_ext_name));
         }
 
         match self.extension_data.get(real_ext_name) {
@@ -340,6 +342,96 @@ mod tests {
     use super::*;
     use std::fs::File;
 
+    #[test]
+    fn allow_installing_remote_extensions() {
+        let rspec: RemoteExtSpec = serde_json::from_value(serde_json::json!({
+            "public_extensions": null,
+            "custom_extensions": null,
+            "library_index": {},
+            "extension_data": {},
+        }))
+        .unwrap();
+
+        rspec
+            .get_ext("ext", false, "latest", "v17")
+            .expect_err("Extension should not be found");
+
+        let rspec: RemoteExtSpec = serde_json::from_value(serde_json::json!({
+            "public_extensions": [],
+            "custom_extensions": null,
+            "library_index": {},
+            "extension_data": {},
+        }))
+        .unwrap();
+
+        rspec
+            .get_ext("ext", false, "latest", "v17")
+            .expect_err("Extension should not be found");
+
+        let rspec: RemoteExtSpec = serde_json::from_value(serde_json::json!({
+            "public_extensions": [],
+            "custom_extensions": [],
+            "library_index": {
+                "ext": "ext"
+            },
+            "extension_data": {
+                "ext": {
+                    "control_data": {
+                        "ext.control": ""
+                    },
+                    "archive_path": ""
+                }
+            },
+        }))
+        .unwrap();
+
+        rspec
+            .get_ext("ext", false, "latest", "v17")
+            .expect_err("Extension should not be found");
+
+        let rspec: RemoteExtSpec = serde_json::from_value(serde_json::json!({
+            "public_extensions": [],
+            "custom_extensions": ["ext"],
+            "library_index": {
+                "ext": "ext"
+            },
+            "extension_data": {
+                "ext": {
+                    "control_data": {
+                        "ext.control": ""
+                    },
+                    "archive_path": ""
+                }
+            },
+        }))
+        .unwrap();
+
+        rspec
+            .get_ext("ext", false, "latest", "v17")
+            .expect("Extension should be found");
+
+        let rspec: RemoteExtSpec = serde_json::from_value(serde_json::json!({
+            "public_extensions": ["ext"],
+            "custom_extensions": [],
+            "library_index": {
+                "ext": "ext"
+            },
+            "extension_data": {
+                "ext": {
+                    "control_data": {
+                        "ext.control": ""
+                    },
+                    "archive_path": ""
+                }
+            },
+        }))
+        .unwrap();
+
+        rspec
+            .get_ext("ext", false, "latest", "v17")
+            .expect("Extension should be found");
+    }
+
     #[test]
     fn parse_spec_file() {
         let file = File::open("tests/cluster_spec.json").unwrap();

test_runner/regress/test_download_extensions.py

@@ -95,6 +95,8 @@ def test_remote_extensions(
 
     # mock remote_extensions spec
     spec: dict[str, Any] = {
+        "public_extensions": ["anon"],
+        "custom_extensions": None,
         "library_index": {
             "anon": "anon",
         },