From 2b0cc04c8def113d176cbc95630b665bdb05d6d9 Mon Sep 17 00:00:00 2001
From: Rami Abdelrazzaq <ramiabdelrazzaq@gmail.com>
Date: Sun, 21 Jun 2026 17:57:06 -0500
Subject: [PATCH] Fix issue #702: Handle CSV with only header row in
 --detect-types (#707)

When inserting a CSV file that contains only a header row (no data rows),
the --detect-types option would crash with an AssertionError because it
tried to transform a table that didn't exist.

This fix adds a check to ensure the table exists before attempting to
apply type transformations. The fix is applied in two places:
1. insert_upsert_implementation() for the insert command
2. memory() command for CSV/TSV files

Added test case: test_insert_csv_headers_only

Co-authored-by: Test User <test@example.com>
---
 sqlite_utils/cli.py      |  4 ++--
 tests/test_cli_insert.py | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/sqlite_utils/cli.py b/sqlite_utils/cli.py
index 1c3ce8d..2f6268f 100644
--- a/sqlite_utils/cli.py
+++ b/sqlite_utils/cli.py
@@ -1177,7 +1177,7 @@ def insert_upsert_implementation(
                 )
             else:
                 raise
-        if tracker is not None:
+        if tracker is not None and db.table(table).exists():
             db.table(table).transform(types=tracker.types)
 
         # Clean up open file-like objects
@@ -2034,7 +2034,7 @@ def memory(
                 rows = (_flatten(row) for row in rows)
 
             db.table(file_table).insert_all(rows, alter=True)
-            if tracker is not None:
+            if tracker is not None and db.table(file_table).exists():
                 db.table(file_table).transform(types=tracker.types)
             # Add convenient t / t1 / t2 views
             view_names = ["t{}".format(i + 1)]
diff --git a/tests/test_cli_insert.py b/tests/test_cli_insert.py
index 9f21b00..5812851 100644
--- a/tests/test_cli_insert.py
+++ b/tests/test_cli_insert.py
@@ -597,3 +597,21 @@ def test_insert_streaming_batch_size_1(db_path):
     proc.stdin.close()
     proc.wait()
     assert proc.returncode == 0
+
+
+def test_insert_csv_headers_only(tmpdir):
+    """Test that CSV with only header row (no data) works with --detect-types (issue #702)"""
+    db_path = str(tmpdir / "test.db")
+    csv_path = str(tmpdir / "headers_only.csv")
+    with open(csv_path, "w") as fp:
+        fp.write("id,name,age\n")
+    # Should not crash with --detect-types (which is now the default)
+    result = CliRunner().invoke(
+        cli.cli,
+        ["insert", db_path, "data", csv_path, "--csv"],
+        catch_exceptions=False,
+    )
+    assert result.exit_code == 0
+    # Table should not exist since there were no data rows
+    db = Database(db_path)
+    assert not db["data"].exists()