--convert function can now modify row in place, closes #371

sqlite_utils/cli.py

@@ -824,7 +824,7 @@ def insert_upsert_implementation(
                 except TypeError:
                     raise click.ClickException("--convert must return dict or iterator")
         else:
-            docs = (fn(doc) for doc in docs)
+            docs = (fn(doc) or doc for doc in docs)
 
     extra_kwargs = {"ignore": ignore, "replace": replace, "truncate": truncate}
     if not_null:
@@ -2225,11 +2225,7 @@ def convert(
     try:
         fn = _compile_code(code, imports)
     except SyntaxError as e:
-        raise click.ClickException(
-            "Syntax error in code:\n\n{}\n\n{}".format(
-                textwrap.indent(e.text.strip(), "    "), e.msg
-            )
-        )
+        raise click.ClickException(str(e))
     if dry_run:
         # Pull first 20 values for first column and preview them
         db.conn.create_function("preview_transform", 1, lambda v: fn(v) if v else v)

sqlite_utils/utils.py

@@ -293,15 +293,25 @@ def _compile_code(code, imports, variable="value"):
         pass
 
     # Try compiling their code as a function instead
-
-    # If single line and no 'return', add the return
+    body_variants = [code]
+    # If single line and no 'return', try adding the return
     if "\n" not in code and not code.strip().startswith("return "):
-        code = "return {}".format(code)
+        body_variants.insert(0, "return {}".format(code))
 
-    new_code = ["def fn({}):".format(variable)]
-    for line in code.split("\n"):
-        new_code.append("    {}".format(line))
-    code_o = compile("\n".join(new_code), "<string>", "exec")
+    code_o = None
+    for variant in body_variants:
+        new_code = ["def fn({}):".format(variable)]
+        for line in variant.split("\n"):
+            new_code.append("    {}".format(line))
+        try:
+            code_o = compile("\n".join(new_code), "<string>", "exec")
+            break
+        except SyntaxError:
+            # Try another variant, e.g. for 'return row["column"] = 1'
+            continue
+
+    if code_o is None:
+        raise SyntaxError("Could not compile code")
 
     for import_ in imports:
         globals[import_.split(".")[0]] = __import__(import_)