fix: preserve configuration completion context

crates/config-source-wasm/src/lib.rs

@@ -101,9 +101,11 @@ pub fn complete_current(
         let utf8_byte_offset = utf16_to_utf8_offset(&source, utf16_offset)?;
         let result = session_environment(snapshot.clone())
             .complete_config(&entrypoint, &source, utf8_byte_offset, explicit)
-            .map_err(|error| JsValue::from_str(&format!("{error:?}")))?
+            .map_err(|error| JsValue::from_str(&format!("{error:?}")))?;
-            .map(|result| WasmCompletionResult {
+        let result = result
-                from: result.from,
+            .map(|result| {
+                Ok::<WasmCompletionResult, JsValue>(WasmCompletionResult {
+                    from: utf8_to_utf16_offset(&source, result.from)?,
                     items: result
                         .items
                         .into_iter()
@@ -114,7 +116,9 @@ pub fn complete_current(
                             priority: item.priority,
                         })
                         .collect(),
-            });
+                })
+            })
+            .transpose()?;
         encode(result)
     })
 }
@@ -177,6 +181,16 @@ fn utf16_to_utf8_offset(source: &str, utf16_offset: usize) -> Result<usize, JsVa
     }
 }
 
+fn utf8_to_utf16_offset(source: &str, utf8_offset: usize) -> Result<usize, JsValue> {
+    if utf8_offset > source.len() {
+        return Err(JsValue::from_str("UTF-8 offset is outside the source"));
+    }
+    if !source.is_char_boundary(utf8_offset) {
+        return Err(JsValue::from_str("UTF-8 offset splits a character"));
+    }
+    Ok(source[..utf8_offset].encode_utf16().count())
+}
+
 fn decode<T: serde::de::DeserializeOwned>(value: JsValue) -> Result<T, JsValue> {
     from_value(value).map_err(|error| JsValue::from_str(&error.to_string()))
 }

crates/config-source/src/lib.rs

@@ -1203,6 +1203,9 @@ impl SnapshotEnvironment {
         {
             let mut member_source = format!("{WORKSPACE_CONFIG_SCHEMA_GLOBAL}.");
             member_source.push_str(&context.schema_path.join("."));
+            if !context.schema_path.is_empty() && context.from == utf8_byte_offset {
+                member_source.push('.');
+            }
             let mut completion = LanguageService::new(self).complete(
                 entrypoint.as_str(),
                 &member_source,
@@ -1961,6 +1964,31 @@ mod tests {
                 .iter()
                 .any(|item| item.label == "default_profile")
         );
+
+        let blank_nested_source = "{ profile = {  } } as WorkspaceConfigSchema";
+        let blank_nested_cursor = blank_nested_source.find("{  }").unwrap() + 2;
+        let blank_nested = environment
+            .complete_config(
+                &path("main.dcdl"),
+                blank_nested_source,
+                blank_nested_cursor,
+                true,
+            )
+            .unwrap()
+            .unwrap();
+        assert_eq!(blank_nested.from, blank_nested_cursor);
+        assert!(
+            blank_nested
+                .items
+                .iter()
+                .any(|item| item.label == "default_profile")
+        );
+        assert!(
+            !blank_nested
+                .items
+                .iter()
+                .any(|item| item.label == "profile")
+        );
     }
 
     #[test]

web/workspace/src/lib/workspace/config-source/ConfigSourceEditor.svelte

@@ -328,10 +328,12 @@
     </header>
     <DecodalSourceEditor
       value={source}
-      readonly={!selectedPath || busy}
+      readonly={!selectedPath || busy || !analysisReady}
       fixedSchemaWrapper={mainSelected}
       onChange={(value) => source = value}
-      onComplete={(value, offset, explicit) => toolchain?.complete(selectedPath, value, offset, explicit) ?? Promise.resolve(null)}
+      onComplete={(value, offset, explicit) => analysisReady && toolchain
+        ? toolchain.complete(selectedPath, value, offset, explicit)
+        : Promise.resolve(null)}
     />
     <p class="config-source-status" aria-live="polite">{status}</p>
     {#if conflict}

web/workspace/test/config-source/wasm-parity.test.ts

@@ -299,6 +299,45 @@ Deno.test("generated WASM returns completion items for the editor adapter", () =
   assertEquals(result.items[0].kind, "file");
 });
 
+Deno.test("generated WASM completes blank nested schema positions after Unicode", () => {
+  const source =
+    '{ description = "日本語"; profile = {  }\n} as WorkspaceConfigSchema';
+  const cursor = source.indexOf("{  }") + 2;
+  set_snapshot({
+    ...snapshot,
+    entries: {
+      ...snapshot.entries,
+      "workspace.dcdl": {
+        ...snapshot.entries["workspace.dcdl"],
+        content: source,
+      },
+    },
+  });
+  set_schema_bundle({
+    contributions: [],
+    source: "{ profile = { default_profile = String; }; prompts = {}; }",
+    fingerprint: "sha256:test-schema",
+  });
+
+  const result = complete_current(
+    "workspace.dcdl",
+    source,
+    cursor,
+    true,
+  ) as {
+    from: number;
+    items: Array<{ label: string; kind: string }>;
+  };
+
+  assertEquals(result.from, cursor);
+  assertEquals(
+    result.items.some((item) => item.label === "default_profile"),
+    true,
+  );
+  assertEquals(result.items.some((item) => item.label === "profile"), false);
+  assertEquals(result.items.some((item) => item.label === "prompts"), false);
+});
+
 Deno.test("generated WASM completes asserted WorkspaceConfigSchema keys", () => {
   const bareSource = "{ pro }";
   const source = "{ pro } as WorkspaceConfigSchema";