From fce0eb4623cf257b2bfb16f816011aafeec77d79 Mon Sep 17 00:00:00 2001
From: Test User <test@example.com>
Date: Sat, 7 Feb 2026 14:12:51 -0600
Subject: [PATCH] Fix issue #702: Handle CSV with only header row in
 --detect-types

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
---
 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 9b9ee20e7..1add5aa4f 100644
--- a/sqlite_utils/cli.py
+++ b/sqlite_utils/cli.py
@@ -1176,7 +1176,7 @@ 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
@@ -2033,7 +2033,7 @@ 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 9f21b0010..58128516a 100644
--- a/tests/test_cli_insert.py
+++ b/tests/test_cli_insert.py
@@ -597,3 +597,21 @@ def try_until(expected):
     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()