Fix #1610 unexpected field-error related to a well-formatted value ex…

…ample of a schema's boolean field using frictionless validate (#1615)

- fixes #1610

This PR fixes the `field-error` which occured doing `frictionless
validate data.csv --schema schema.json` with a `TableSchema` `schema`
containing a `BooleanField` customised with 'trueValues' or
'falseValues' and 'example' value , for example:
```
schema.json
----
{
  "$schema": "https://frictionlessdata.io/schemas/table-schema.json",
  "fields": [
    {
      "name": "IsTrue",
      "type": "boolean",
      "trueValues": ["yes"],
      "falseValues": ["no"],
      "example": "yes"
    }
  ]
}
```
```
data.csv
----
isTrue
yes
no
```

This PR add tests cases to ensure that example value is correctly
evaluated according to customized 'trueValues' or 'falseValues', as
expected.

---------

Co-authored-by: Pierre Camilleri <[email protected]>

frictionless/fields/__spec__/test_boolean.py

@@ -1,6 +1,8 @@
 import pytest
 
-from frictionless import Field
+from frictionless import Field, Schema
+from frictionless.errors.metadata import SchemaError
+from frictionless.exception import FrictionlessException
 
 # General
 
@@ -32,12 +34,70 @@
         ("default", "3.14", None, {}),
         ("default", "", None, {}),
         ("default", "Yes", None, {"trueValues": ["yes"]}),
+        ("default", "true", None, {"trueValues": ["yes"]}),
+        ("default", "True", None, {"trueValues": ["yes"]}),
+        ("default", "TRUE", None, {"trueValues": ["yes"]}),
+        ("default", "1", None, {"trueValues": ["yes"]}),
         ("default", "No", None, {"falseValues": ["no"]}),
+        ("default", "false", None, {"falseValues": ["no"]}),
+        ("default", "False", None, {"falseValues": ["no"]}),
+        ("default", "FALSE", None, {"falseValues": ["no"]}),
+        ("default", "0", None, {"falseValues": ["no"]}),
     ],
 )
 def test_boolean_read_cell(format, source, target, options):
     descriptor = {"name": "name", "type": "boolean", "format": format}
     descriptor.update(options)
     field = Field.from_descriptor(descriptor)
-    cell, notes = field.read_cell(source)
+    cell, _ = field.read_cell(source)
     assert cell == target
+
+    schema_descriptor = {"fields": [{"name": "IsTrue", "type": "boolean"}]}
+    schema_descriptor["fields"][0].update(options)
+    schema = Schema.from_descriptor(schema_descriptor)
+    fields = schema.fields
+    cell, _ = fields[0].read_cell(source)
+    assert cell == target
+
+
+@pytest.mark.parametrize(
+    "source, target, options",
+    [
+        (True, True, {"trueValues": ["yes"], "example": "yes"}),
+        ("yes", True, {"trueValues": ["yes"], "example": "yes"}),
+        ("true", None, {"trueValues": ["yes"], "example": "yes"}),
+        (False, False, {"falseValues": ["no"], "example": "no"}),
+        ("no", False, {"falseValues": ["no"], "example": "no"}),
+        ("false", None, {"falseValues": ["no"], "example": "no"}),
+    ],
+)
+def test_boolean_from_schema_descriptor_with_valid_example_fix_issue_1610(
+    source, target, options
+):
+    schema_descriptor = {
+        "$schema": "https://frictionlessdata.io/schemas/table-schema.json",
+        "fields": [{"name": "IsTrue", "type": "boolean"}],
+    }
+    schema_descriptor["fields"][0].update(options)
+    schema = Schema.from_descriptor(schema_descriptor)
+    fields = schema.fields
+    cell, _ = fields[0].read_cell(source)
+    assert cell == target
+
+
+def test_boolean_from_schema_descriptor_with_invalid_example_fix_issue_1610():
+    schema_descriptor = {
+        "$schema": "https://frictionlessdata.io/schemas/table-schema.json",
+        "fields": [
+            {
+                "name": "IsTrue",
+                "type": "boolean",
+                "falseValues": ["no"],
+                "example": "invalid",
+            }
+        ],
+    }
+    with pytest.raises(FrictionlessException) as excinfo:
+        Schema.from_descriptor(schema_descriptor)
+    err = excinfo.value.error
+    assert isinstance(err, SchemaError)

frictionless/schema/field.py

@@ -50,7 +50,9 @@ class Field(Metadata):
     For example: "default","array" etc.
     """
 
-    missing_values: List[str] = attrs.field(factory=settings.DEFAULT_MISSING_VALUES.copy)
+    missing_values: List[str] = attrs.field(
+        factory=settings.DEFAULT_MISSING_VALUES.copy
+    )
     """
     List of string values to be set as missing values in the field. If any of string in missing values
     is found in the field value then it is set as None.
@@ -260,13 +262,23 @@ def metadata_validate(cls, descriptor: IDescriptor):  # type: ignore
         if example:
             type = descriptor.get("type")
             Class = system.select_field_class(type)
+
             field = Class(
-                name=descriptor.get("name", "example"),
-                format=descriptor.get("format", "default"),  # type: ignore
+                name=descriptor.get("name"),  # type: ignore
+                format=descriptor.get("format", "default"),
             )
+
+            if type == "boolean":
+                # 'example' value must be compared to customized 'trueValues' and 'falseValues'
+                if "trueValues" in descriptor.keys():
+                    field.true_values = descriptor["trueValues"]
+                if "falseValues" in descriptor.keys():
+                    field.false_values = descriptor["falseValues"]
             _, notes = field.read_cell(example)
             if notes is not None:
-                note = f'example value "{example}" for field "{field.name}" is not valid'
+                note = (
+                    f'example value "{example}" for field "{field.name}" is not valid'
+                )
                 yield errors.FieldError(note=note)
 
         # Misleading