Add CSV Dialect pydantic class

.github/workflows/ci_template.yml

@@ -9,7 +9,7 @@ on:
         type: string
       python-version:
         description: 'Python version'
-        default: '["3.12"]'
+        default: '["3.9", "3.12"]'
         type: string
 
 jobs:

.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+    "python.testing.pytestArgs": ["--no-cov"],
+    "python.testing.unittestEnabled": false,
+    "python.testing.pytestEnabled": true
+}

csvy/validators.py

@@ -0,0 +1,127 @@
+import csv
+from typing import Optional, Type, TypeVar
+
+from pydantic import BaseModel, Field
+
+# Create a generic variable that can be 'Parent', or any subclass.
+T = TypeVar("T", bound="CSVDialectValidator")
+
+
+class CSVDialectValidator(BaseModel):
+    """Implements a validator for CSV Dialects.
+
+    This class is used to validate the CSV Dialects in the CSVY file. It is based on the
+    `csv.Dialect` class from the Python Standard Library. It does not include the
+    'quoting' attribute, as it is not serializable as JSON or easy to understand by
+    other tools, but rather a python specific thing.
+
+    Attributes:
+        delimiter: A one-character string used to separate fields.
+        doublequote: Controls how instances of quotechar appearing inside a field should
+            themselves be quoted. When True, the character is doubled. When False, the
+            escapechar is used as a prefix to the quotechar. It defaults to True.
+        escapechar: A one-character string used by the writer to escape the delimiter.
+            It defaults to None.
+        lineterminator: The string used to terminate lines produced by the writer. It
+            defaults to '\\r\\n'.
+        quotechar: A one-character string used to quote fields containing special
+            characters, such as the delimiter or quotechar, or which contain new-line
+            characters. It defaults to '"'.
+        skipinitialspace: When True, whitespace immediately following the delimiter is
+            ignored. It defaults to False.
+    """
+
+    delimiter: str = Field(default=",")
+    doublequote: bool = Field(default=True)
+    escapechar: Optional[str] = Field(default=None)
+    lineterminator: str = Field(default="\r\n")
+    quotechar: str = Field(default='"')
+    skipinitialspace: bool = Field(default=False)
+
+    def to_dialect(self) -> csv.Dialect:
+        """Converts the validator to a custom csv.Dialect object.
+
+        This method converts the validator to a custom csv.Dialect object that can be
+        used to read or write CSV files with the specified dialect.
+
+        For 'quoting', the default value is used, as it is not serializable.
+
+        Returns:
+            A custom csv.Dialect object with the specified attributes.
+        """
+        dialect = type(
+            "CustomDialect",
+            (csv.Dialect,),
+            {
+                "delimiter": self.delimiter,
+                "doublequote": self.doublequote,
+                "escapechar": self.escapechar,
+                "lineterminator": self.lineterminator,
+                "quotechar": self.quotechar,
+                "skipinitialspace": self.skipinitialspace,
+                "quoting": csv.QUOTE_MINIMAL,  # This is not serializable.
+            },
+        )
+        return dialect()
+
+    @classmethod
+    def excel(cls: Type[T]) -> T:
+        """Returns a validator for the Excel CSV Dialect.
+
+        This method returns a validator for the Excel CSV Dialect, which is a common
+        dialect used in Excel files.
+
+        Returns:
+            A validator for the Excel CSV Dialect.
+        """
+        excel = csv.excel()
+        return cls(
+            delimiter=excel.delimiter,
+            doublequote=excel.doublequote,
+            escapechar=excel.escapechar,
+            lineterminator=excel.lineterminator,
+            quotechar=excel.quotechar,
+            skipinitialspace=excel.skipinitialspace,
+        )
+
+    @classmethod
+    def excel_tab(cls: Type[T]) -> T:
+        """Returns a validator for the Excel Tab CSV Dialect.
+
+        This method returns a validator for the Excel Tab CSV Dialect, which is a common
+        dialect used in Excel files with tab delimiters.
+
+        `excel` has not parameter `strict` so that one is ignored.
+
+        Returns:
+            A validator for the Excel Tab CSV Dialect.
+        """
+        excel_tab = csv.excel_tab()
+        return cls(
+            delimiter=excel_tab.delimiter,
+            doublequote=excel_tab.doublequote,
+            escapechar=excel_tab.escapechar,
+            lineterminator=excel_tab.lineterminator,
+            quotechar=excel_tab.quotechar,
+            skipinitialspace=excel_tab.skipinitialspace,
+        )
+
+    @classmethod
+    def unix_dialect(cls: Type[T]) -> T:
+        """Returns a validator for the Unix CSV Dialect.
+
+        This method returns a validator for the Unix CSV Dialect, which is a common
+        dialect used in Unix files.
+
+        Returns:
+            A validator for the Unix CSV Dialect.
+        """
+        unix = csv.unix_dialect()
+        return cls(
+            delimiter=unix.delimiter,
+            doublequote=unix.doublequote,
+            escapechar=unix.escapechar,
+            lineterminator=unix.lineterminator,
+            quotechar=unix.quotechar,
+            skipinitialspace=unix.skipinitialspace,
+        )