Disabling input_format_with_names_use_header discards all the input

[depressed-pho]

Describe the bug
When you set the setting input_format_with_names_use_header to 0, INSERT does not actually insert rows.

How to reproduce

• Which ClickHouse server version to use: git master a21fe0b492cbc8628126a3cd493b83e82abf9978, checked out on 2021-03-31
• Which interface to use: the native command-line client
• Non-default settings, if any: input_format_with_names_use_header = 0
• CREATE TABLE statements for all tables involved:

CREATE TABLE csvtest
(
    `t` String
)
ENGINE = MergeTree
ORDER BY t

• Sample data for all these tables
  test.csv:

t
testdata1
testdata2

• Queries to run that lead to unexpected result:

% clickhouse-client --input_format_with_names_use_header 0 --query "INSERT INTO csvtest FORMAT CSVWithNames" < test.csv

Expected behavior
Two rows ('testdata1'), ('testdata2') will be inserted to the table csvtest.

Error message and/or stacktrace
Nothing. It silently discards the input and inserts nothing to the table.

Additional context
It works as expected if you set input_format_with_names_use_header to 1.

[nikitamikhaylov]

What will be if you set input_format_parallel_parsing=0 ?

[depressed-pho]

I got the same result If I set both input_format_parallel_parsing and input_format_with_names_use_header to 0. That is, rows were still not inserted.