From c8b7822d0d9febca76ed8a7e4a4801cacbc19382 Mon Sep 17 00:00:00 2001
From: Kerollmops <clement@meilisearch.com>
Date: Sat, 19 Apr 2025 12:22:37 +0200
Subject: [PATCH] Allow users to delete documents

---
 crates/milli/src/update/new/document.rs       | 41 ++++++++++++-------
 .../update/new/indexer/document_operation.rs  | 14 ++++++-
 2 files changed, 39 insertions(+), 16 deletions(-)

diff --git a/crates/milli/src/update/new/document.rs b/crates/milli/src/update/new/document.rs
index e6178d1df..0de14ba22 100644
--- a/crates/milli/src/update/new/document.rs
+++ b/crates/milli/src/update/new/document.rs
@@ -412,7 +412,7 @@ impl<'doc> Versions<'doc> {
         engine: &rhai::Engine,
         edit_function: &rhai::AST,
         doc_alloc: &'doc bumpalo::Bump,
-    ) -> Result<Option<Self>> {
+    ) -> Result<Option<Option<Self>>> {
         let Some(data) = versions.next() else { return Ok(None) };
 
         let mut doc = doc.unwrap_or_default();
@@ -431,12 +431,19 @@ impl<'doc> Versions<'doc> {
 
             let _ = engine.eval_ast_with_scope::<rhai::Dynamic>(&mut scope, edit_function).unwrap();
             data = RawMap::with_hasher_in(FxBuildHasher, doc_alloc);
-            for (key, value) in scope.get_value::<rhai::Map>("doc").unwrap() {
-                let mut vec = bumpalo::collections::Vec::new_in(doc_alloc);
-                serde_json::to_writer(&mut vec, &value).unwrap();
-                let key = doc_alloc.alloc_str(key.as_str());
-                let raw_value = serde_json::from_slice(vec.into_bump_slice()).unwrap();
-                data.insert(key, raw_value);
+            match scope.get_value::<Option<rhai::Map>>("doc").unwrap() {
+                Some(map) => {
+                    for (key, value) in map {
+                        let mut vec = bumpalo::collections::Vec::new_in(doc_alloc);
+                        serde_json::to_writer(&mut vec, &value).unwrap();
+                        let key = doc_alloc.alloc_str(key.as_str());
+                        let raw_value = serde_json::from_slice(vec.into_bump_slice()).unwrap();
+                        data.insert(key, raw_value);
+                    }
+                }
+                // In case the deletes the document and it's not the last change
+                // we simply set the document to an empty one and await the next change.
+                None => (),
             }
         }
 
@@ -449,15 +456,19 @@ impl<'doc> Versions<'doc> {
 
         let _ = engine.eval_ast_with_scope::<rhai::Dynamic>(&mut scope, edit_function).unwrap();
         data = RawMap::with_hasher_in(FxBuildHasher, doc_alloc);
-        for (key, value) in scope.get_value::<rhai::Map>("doc").unwrap() {
-            let mut vec = bumpalo::collections::Vec::new_in(doc_alloc);
-            serde_json::to_writer(&mut vec, &value).unwrap();
-            let key = doc_alloc.alloc_str(key.as_str());
-            let raw_value = serde_json::from_slice(vec.into_bump_slice()).unwrap();
-            data.insert(key, raw_value);
+        match scope.get_value::<Option<rhai::Map>>("doc").unwrap() {
+            Some(map) => {
+                for (key, value) in map {
+                    let mut vec = bumpalo::collections::Vec::new_in(doc_alloc);
+                    serde_json::to_writer(&mut vec, &value).unwrap();
+                    let key = doc_alloc.alloc_str(key.as_str());
+                    let raw_value = serde_json::from_slice(vec.into_bump_slice()).unwrap();
+                    data.insert(key, raw_value);
+                }
+                Ok(Some(Some(Self::single(data))))
+            }
+            None => Ok(Some(None)),
         }
-
-        Ok(Some(Self::single(data)))
     }
 
     pub fn single(version: RawMap<'doc, FxBuildHasher>) -> Self {
diff --git a/crates/milli/src/update/new/indexer/document_operation.rs b/crates/milli/src/update/new/indexer/document_operation.rs
index e3ac7b35d..96488c37c 100644
--- a/crates/milli/src/update/new/indexer/document_operation.rs
+++ b/crates/milli/src/update/new/indexer/document_operation.rs
@@ -510,6 +510,7 @@ impl<'pl> PayloadOperations<'pl> {
     }
 
     /// Returns only the most recent version of a document based on the updates from the payloads.
+    #[allow(clippy::too_many_arguments)]
     fn merge<'doc>(
         &self,
         rtxn: &heed::RoTxn,
@@ -587,7 +588,18 @@ impl<'pl> PayloadOperations<'pl> {
                             .get(rtxn, &self.docid)?
                             .map(|obkv| obkv_to_rhaimap(obkv, fidmap))
                             .transpose()?;
-                        Versions::multiple_with_edits(doc, versions, engine, ast, doc_alloc)?
+                        match Versions::multiple_with_edits(doc, versions, engine, ast, doc_alloc)?
+                        {
+                            Some(Some(versions)) => Some(versions),
+                            Some(None) if self.is_new => return Ok(None),
+                            Some(None) => {
+                                return Ok(Some(DocumentChange::Deletion(Deletion::create(
+                                    self.docid,
+                                    external_doc,
+                                ))));
+                            }
+                            None => None,
+                        }
                     }
                     None => Versions::multiple(versions)?,
                 };