Send console errors to stderr instead of stdout (#1792)

- fixes #1749

---

`print_error` and `print_exception` rendered onto whatever console the
command passed in, and every command builds a plain stdout `Console()`.
So the reporter's case does this:

```
$ frictionless describe doesnotexist.csv --json > out.txt 2> err.txt
before:  stdout 324 bytes (the red error panel), stderr 0 bytes
after:   stdout 0 bytes,                          stderr 324 bytes
```

Both helpers now print to a module-level `Console(stderr=True)`,
including the `debug=True` path, which called
`console.print_exception()` and would otherwise have kept leaking
tracebacks to stdout.

There is one call site in there that must **not**
move:

`extract.py:233` calls `print_error(console, note="No rows found",
title="Empty")` from inside the table-rendering loop, after
`console.rule("[bold]Tables")` and followed by `continue`. That is
report content on a **successful** run (exit 0) using `print_error`
purely for the red panel styling. Sending it to stderr would tear it out
of the sequence of tables it sits between. So it moves to a new
`print_panel` helper that renders on the passed console. Verified:
`frictionless extract empty.csv` still prints "No rows found" to stdout,
exit 0, with stderr empty.

**Tests.** Five console tests asserted error text on `result.stdout`;
they now assert on `result.stderr`, which is precisely the behaviour
under change:

- `test_describe.py::test_console_describe_error_not_found`
-
`test_transform.py::test_console_transform_error_not_found_source_issue_814`
- `test_validate.py::test_console_validate_single_invalid_resource_221`
- `test_extract.py::test_console_extract_single_invalid_resource`
-
`test_extract.py::test_console_extract_single_valid_resource_invalid_package`

Two new tests pin the separation directly: an error run must leave
stdout completely empty while stderr carries the message, and a
successful `--json` run must still produce parseable JSON on stdout with
stderr empty. Reverting the source while keeping the tests fails the
first of those; the second passes either way, deliberately, so it
catches over-correction.

---------

Co-authored-by: Pierre Camilleri <pierre.camilleri@multi.coop>
Co-authored-by: Pierre Camilleri <22995923+pierrecamilleri@users.noreply.github.com>

Author: DMZ22

frictionless/console/commands/__spec__/conftest.py

@@ -0,0 +1,16 @@
+from __future__ import annotations
+
+from typer.testing import CliRunner
+
+
+def create_runner() -> CliRunner:
+    """Build a runner capturing stdout and stderr separately.
+
+    click >= 8.2 always separates the two streams and dropped the "mix_stderr"
+    argument, while earlier versions merge them unless it is passed. Python 3.9
+    is stuck on click 8.1 because 8.2 requires Python 3.10.
+    """
+    try:
+        return CliRunner(mix_stderr=False)  # type: ignore[call-arg]
+    except TypeError:
+        return CliRunner()

frictionless/console/commands/__spec__/test_describe.py

@@ -2,12 +2,13 @@
 
 import pytest
 import yaml
-from typer.testing import CliRunner
 
 from frictionless import Detector, Dialect, describe, formats, platform
 from frictionless.console import console
 
-runner = CliRunner()
+from .conftest import create_runner
+
+runner = create_runner()
 
 
 # General
@@ -106,8 +107,8 @@ def test_console_describe_json():
 def test_console_describe_error_not_found():
     actual = runner.invoke(console, "describe data/bad.csv")
     assert actual.exit_code == 1
-    assert actual.stdout.count("[Errno 2]")
-    assert actual.stdout.count("data/bad.csv")
+    assert actual.stderr.count("[Errno 2]")
+    assert actual.stderr.count("data/bad.csv")
 
 
 def test_console_describe_basepath():
@@ -199,3 +200,17 @@ def test_console_describe_package_with_glob_having_one_incorrect_dialect_1126():
     assert output["resources"][1]["schema"] == {
         "fields": [{"type": "string", "name": "# Author: the scientist"}]
     }
+
+
+def test_console_describe_error_goes_to_stderr_not_stdout_issue_1749():
+    actual = runner.invoke(console, "describe data/bad.csv --json")
+    assert actual.exit_code == 1
+    assert "[Errno 2]" in actual.stderr
+    assert actual.stdout == ""
+
+
+def test_console_describe_success_still_writes_to_stdout_issue_1749():
+    actual = runner.invoke(console, "describe data/table.csv --json")
+    assert actual.exit_code == 0
+    assert json.loads(actual.stdout)
+    assert actual.stderr == ""

frictionless/console/commands/__spec__/test_extract.py

@@ -2,12 +2,13 @@
 
 import pytest
 import yaml
-from typer.testing import CliRunner
 
 from frictionless import Detector, Dialect, extract, formats, platform
 from frictionless.console import console
 
-runner = CliRunner()
+from .conftest import create_runner
+
+runner = create_runner()
 
 
 # General
@@ -275,15 +276,15 @@ def test_console_extract_single_invalid_resource():
         console, "extract data/datapackage.json --resource-name number-twoo"
     )
     assert actual.exit_code == 1
-    assert actual.stdout.count("number-twoo")
+    assert actual.stderr.count("number-twoo")
 
 
 def test_console_extract_single_valid_resource_invalid_package():
     actual = runner.invoke(
         console, "extract data/bad/datapackage.json --resource-name number-two"
     )
     assert actual.exit_code == 1
-    assert actual.stdout.count("No such file or directory")
+    assert actual.stderr.count("No such file or directory")
 
 
 def test_console_extract_single_resource_yaml():

frictionless/console/commands/__spec__/test_transform.py

@@ -1,8 +1,8 @@
-from typer.testing import CliRunner
-
 from frictionless.console import console
 
-runner = CliRunner()
+from .conftest import create_runner
+
+runner = create_runner()
 
 
 def test_console_transform():
@@ -35,5 +35,5 @@ def test_console_transform_error_not_found_source_issue_814():
         "transform data/bad.csv --pipeline data/issue-814.yaml",
     )
     assert result.exit_code == 1
-    assert result.stdout.count("[Errno 2]")
-    assert result.stdout.count("bad.csv")
+    assert result.stderr.count("[Errno 2]")
+    assert result.stderr.count("bad.csv")

frictionless/console/commands/__spec__/test_validate.py

@@ -2,12 +2,13 @@
 
 import pytest
 import yaml
-from typer.testing import CliRunner
 
 from frictionless import Detector, Dialect, validate
 from frictionless.console import console
 
-runner = CliRunner()
+from .conftest import create_runner
+
+runner = create_runner()
 
 
 # General
@@ -222,7 +223,7 @@ def test_console_validate_single_invalid_resource_221():
         console, "validate data/datapackage.json --resource-name number-twoo"
     )
     assert actual.exit_code == 1
-    assert actual.stdout.count("number-twoo")
+    assert actual.stderr.count("number-twoo")
 
 
 def test_console_validate_multipart_resource_1140():

frictionless/console/commands/convert.py

@@ -63,7 +63,7 @@ def console_convert(
     source = helpers.create_source(source, path=path)
     if not source and not path:
         note = 'Providing "source" or "path" is required'
-        helpers.print_error(console, note=note)
+        helpers.print_error(note=note)
         raise typer.Exit(code=1)
 
     try:
@@ -124,7 +124,7 @@ def console_convert(
                 )
 
     except Exception as exception:
-        helpers.print_exception(console, debug=debug, exception=exception)
+        helpers.print_exception(debug=debug, exception=exception)
         raise typer.Exit(code=1)
 
     # Print result

frictionless/console/commands/describe.py

@@ -76,7 +76,7 @@ def console_describe(
     source = helpers.create_source(source, path=path)
     if not source and not path:
         note = 'Providing "source" or "path" is required'
-        helpers.print_error(console, note=note)
+        helpers.print_error(note=note)
         raise typer.Exit(code=1)
 
     try:
@@ -121,7 +121,7 @@ def console_describe(
             stats=stats,
         )
     except Exception as exception:
-        helpers.print_exception(console, debug=debug, exception=exception)
+        helpers.print_exception(debug=debug, exception=exception)
         raise typer.Exit(code=1)
 
     # Json mode

frictionless/console/commands/explore.py

@@ -4,7 +4,6 @@
 from typing import List
 
 import typer
-from rich.console import Console
 
 from ...resource import Resource
 from ...system import system
@@ -29,8 +28,6 @@ def console_explore(
     Please read the commands reference:
     - https://www.visidata.org/man/
     """
-    console = Console()
-
     # Setup system
     if trusted:
         system.trusted = trusted
@@ -41,7 +38,7 @@ def console_explore(
     source = helpers.create_source(source, path=path)
     if not source and not path:
         note = 'Providing "source" or "path" is required'
-        helpers.print_error(console, note=note)
+        helpers.print_error(note=note)
         raise typer.Exit(code=1)
 
     # Get paths
@@ -55,7 +52,7 @@ def console_explore(
         resources = resource.list(name=name)
         paths = [resource.normpath for resource in resources if resource.normpath]
     except Exception as exception:
-        helpers.print_exception(console, debug=debug, exception=exception)
+        helpers.print_exception(debug=debug, exception=exception)
         raise typer.Exit(code=1)
 
     # Enter editor

frictionless/console/commands/extract.py

@@ -90,7 +90,7 @@ def console_extract(
     source = helpers.create_source(source, path=path)
     if not source and not path:
         note = 'Providing "source" or "path" is required'
-        helpers.print_error(console, note=note)
+        helpers.print_error(note=note)
         raise typer.Exit(code=1)
 
     try:
@@ -173,7 +173,7 @@ def console_extract(
         # List resources
         resources = resource.list()
     except Exception as exception:
-        helpers.print_exception(console, debug=debug, exception=exception)
+        helpers.print_exception(debug=debug, exception=exception)
         raise typer.Exit(code=1)
 
     # Yaml mode
@@ -191,7 +191,7 @@ def console_extract(
     # No data
     if not data:
         note = "No tabular data have been found in the source"
-        helpers.print_error(console, note=note)
+        helpers.print_error(note=note)
         raise typer.Exit(code=1)
 
     # TODO: rework
@@ -230,7 +230,7 @@ def console_extract(
     for title, items in data.items():
         # Empty
         if not items:
-            helpers.print_error(console, note="No rows found", title="Empty")
+            helpers.print_panel(console, note="No rows found", title="Empty")
             continue
 
         # General

frictionless/console/commands/index.py

@@ -41,7 +41,7 @@ def console_index(
     source = helpers.create_source(source, path=path)
     if not source and not path:
         note = 'Providing "source" or "path" is required'
-        helpers.print_error(console, note=note)
+        helpers.print_error(note=note)
         raise typer.Exit(code=1)
 
     # Index resource
@@ -71,7 +71,7 @@ def console_index(
                 )
             )
     except Exception as exception:
-        helpers.print_exception(console, debug=debug, exception=exception)
+        helpers.print_exception(debug=debug, exception=exception)
         raise typer.Exit(code=1)
 
     # Print result