Proof of concept for Plugin system (fixes #3562)

.gitignore

@@ -34,3 +34,6 @@ dev_pgdata/
 
 # database dumps
 *.sqldump
+
+# compiled example plugin
+example_plugin/plugin.wasm

api_tests/prepare-drone-federation-test.sh

@@ -49,8 +49,6 @@ else
   done
 fi
 
-echo "$PWD"
-
 LOG_DIR=target/log
 mkdir -p $LOG_DIR
 
@@ -75,6 +73,11 @@ LEMMY_CONFIG_LOCATION=./docker/federation/lemmy_delta.hjson \
   LEMMY_DATABASE_URL="${LEMMY_DATABASE_URL}/lemmy_delta" \
   target/lemmy_server >$LOG_DIR/lemmy_delta.out 2>&1 &
 
+# plugin setup
+pushd example_plugin
+tinygo build -o plugin.wasm -target wasi main.go
+popd
+
 echo "start epsilon"
 # An instance who has a blocklist, with lemmy-alpha blocked
 LEMMY_CONFIG_LOCATION=./docker/federation/lemmy_epsilon.hjson \

api_tests/run-federation-test.sh

@@ -11,7 +11,7 @@ killall -s1 lemmy_server || true
 popd
 
 pnpm i
-pnpm api-test || true
+pnpm api-test-post || true
 
 killall -s1 lemmy_server || true
 killall -s1 pict-rs || true

api_tests/src/post.spec.ts

@@ -763,3 +763,14 @@ test("Fetch post with redirect", async () => {
   let gammaPost2 = await gamma.resolveObject(form);
   expect(gammaPost2.post).toBeDefined();
 });
+
+test("Create a post", async () => {
+  let community = await createCommunity(epsilon);
+  let postRes = createPost(
+    epsilon,
+    community.community_view.community.id,
+    "https://example.com/",
+    "plugin should block this",
+  );
+  await expect(postRes).rejects.toStrictEqual(Error("plugin_error"));
+});

crates/api_crud/Cargo.toml

@@ -28,8 +28,11 @@ uuid = { workspace = true }
 moka.workspace = true
 once_cell.workspace = true
 anyhow.workspace = true
+serde.workspace = true
 webmention = "0.5.0"
 accept-language = "3.1.0"
+extism = "1.2.0"
+extism-convert = "1.2.0"
 
 [package.metadata.cargo-machete]
 ignored = ["futures"]

crates/api_crud/src/post/create.rs

@@ -1,5 +1,6 @@
 use activitypub_federation::config::Data;
 use actix_web::web::Json;
+use extism::*;
 use lemmy_api_common::{
   build_response::build_post_response,
   context::LemmyContext,
@@ -46,6 +47,8 @@ use lemmy_utils::{
     },
   },
 };
+use serde::Serialize;
+use std::{ffi::OsStr, fs::read_dir};
 use tracing::Instrument;
 use url::Url;
 use webmention::{Webmention, WebmentionError};
@@ -123,6 +126,8 @@ pub async fn create_post(
     }
   };
 
+  plugin_hook("api_create_post", data.clone())?;
+
   let post_form = PostInsertForm::builder()
     .name(data.name.trim().to_string())
     .url(url)
@@ -202,3 +207,31 @@ pub async fn create_post(
 
   build_post_response(&context, community_id, &local_user_view.person, post_id).await
 }
+
+fn load_plugins() -> LemmyResult<Plugin> {
+  // TODO: make dir configurable via env var
+  let plugin_paths = read_dir("example_plugin")?;
+
+  let mut wasm_files = vec![];
+  for path in plugin_paths {
+    let path = path?.path();
+    if path.extension() == Some(OsStr::new("wasm")) {
+      wasm_files.push(path);
+    }
+  }
+  let manifest = Manifest::new(wasm_files);
+  let plugin = Plugin::new(&manifest, [], true)?;
+  Ok(plugin)
+}
+
+fn plugin_hook<T: Serialize>(name: &'static str, data: T) -> LemmyResult<()> {
+  let mut plugin = load_plugins()?;
+  if plugin.function_exists(name) {
+    let res = plugin
+      .call::<extism_convert::Json<T>, &str>(name, data.into())
+      .map_err(|e| LemmyErrorType::PluginError(e.to_string()));
+    dbg!(&res);
+    println!("{}", res?);
+  }
+  Ok(())
+}

crates/utils/src/error.rs

@@ -177,6 +177,7 @@ pub enum LemmyErrorType {
   InvalidBotAction,
   CantBlockLocalInstance,
   UrlWithoutDomain,
+  PluginError(String),
   Unknown(String),
 }
 

example_plugin/go.mod

@@ -0,0 +1,5 @@
+module example_plugin
+
+go 1.22.0
+
+require github.com/extism/go-pdk v1.0.2 // indirect

example_plugin/go.sum

@@ -0,0 +1,2 @@
+github.com/extism/go-pdk v1.0.2 h1:UB7oTW3tw2zoMlsUdBEDAAbhQg9OudzgNeyCwQYZ730=
+github.com/extism/go-pdk v1.0.2/go.mod h1:Gz+LIU/YCKnKXhgge8yo5Yu1F/lbv7KtKFkiCSzW/P4=

example_plugin/main.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"github.com/extism/go-pdk"
+	"errors"
+)
+
+type CreatePost struct {
+	Name string `json:"name"`
+	Body string `json:"body"`
+	// skipping other fields for now
+  }
+
+//export api_create_post
+func api_create_post() int32 {
+	params := CreatePost{}
+	// use json input helper, which automatically unmarshals the plugin input into your struct
+	err := pdk.InputJSON(&params)
+	if err != nil {
+		pdk.SetError(err)
+		return 1
+	}
+	if params.Body == "plugin should block this" {
+		pdk.SetError(errors.New("blocked by plugin"))
+		return 1
+	}
+	greeting := `Created post "` + params.Name + `"!`
+	pdk.OutputString(greeting)
+	return 0
+}
+
+func main() {}