Implement export snippet.

src/wasm/export_snippet.rs

@@ -4,15 +4,15 @@ use serde::Serialize;
 use super::ast_node::WasmAstNode;
 use super::macros::to_wasm;
 use super::to_wasm::ToWasm;
-use super::AdditionalProperties;
 use crate::compare::ElispFact;
 use crate::types::ExportSnippet;
 use crate::wasm::to_wasm::ToWasmStandardProperties;
 
 #[derive(Debug, Serialize, Deserialize)]
 pub struct WasmExportSnippet {
-    #[serde(flatten)]
-    pub(crate) additional_properties: AdditionalProperties,
+    #[serde(rename = "back-end")]
+    pub(crate) backend: String,
+    pub(crate) value: Option<String>,
 }
 
 to_wasm!(
@@ -21,12 +21,13 @@ to_wasm!(
     original,
     wasm_context,
     { WasmAstNode::ExportSnippet(original) },
-    { "TODO".into() },
+    { "export-snippet".into() },
     {
         Ok((
             Vec::new(),
             WasmExportSnippet {
-                additional_properties: AdditionalProperties::default(),
+                backend: original.backend.to_owned(),
+                value: original.contents.map(|s| s.to_owned()),
             },
         ))
     }