Add new CSV transform subcommand #361

 * The goal of this would be to replace entirely the mapping feature
   and options.

Signed-off-by: Philippe Ombredanne <[email protected]>

Author: pombredanne

src/attributecode/cmd.py

@@ -494,6 +494,84 @@ def check(location, verbose):
     sys.exit(severe_errors_count)
 
 
+######################################################################
+# transform subcommand
+######################################################################
+
+def print_config_help(ctx, param, value):
+    if not value or ctx.resilient_parsing:
+        return
+    from attributecode.transform import tranformer_config_help
+    click.echo(tranformer_config_help)
+    ctx.exit()
+
+
+@about.command(cls=AboutCommand,
+    short_help='Transform a CSV by applying renamings, filters and checks.')
+
+@click.argument('location',
+    required=True,
+    callback=partial(validate_extensions, extensions=('.csv',)),
+    metavar='LOCATION',
+    type=click.Path(exists=True, dir_okay=False, readable=True, resolve_path=True))
+
+@click.argument('output',
+    required=True,
+    callback=partial(validate_extensions, extensions=('.csv',)),
+    metavar='OUTPUT',
+    type=click.Path(exists=False, dir_okay=False, writable=True, resolve_path=True))
+
+@click.option('-c', '--configuration',
+    metavar='FILE',
+    type=click.Path(exists=True, dir_okay=False, readable=True, resolve_path=True),
+    help='Path to an optional YAML configuration file. See --help-format for '
+         'format help.')
+
+@click.option('--help-format',
+    is_flag=True, is_eager=True, expose_value=False,
+    callback=print_config_help,
+    help='Show configuration file format help and exit.')
+
+@click.option('-q', '--quiet',
+    is_flag=True,
+    help='Do not print error or warning messages.')
+
+@click.option('--verbose',
+    is_flag=True,
+    help='Show all error and warning messages.')
+
+@click.help_option('-h', '--help')
+
+def transform(location, output, configuration, quiet, verbose):  # NOQA
+    """
+Transform the CSV file at LOCATION by applying renamings, filters and checks 
+and write a new CSV to OUTPUT.
+
+LOCATION: Path to a CSV file.
+
+OUTPUT: Path to CSV inventory file to create.
+    """
+    from attributecode.transform import transform_csv_to_csv
+    from attributecode.transform import Transformer
+
+    if not quiet:
+        print_version()
+        click.echo('Transforming CSV...')
+
+    if not configuration:
+        transformer = Transformer.default()
+    else:
+        transformer = Transformer.from_file(configuration)
+
+    errors = transform_csv_to_csv(location, output, transformer)
+
+    errors_count = report_errors(errors, quiet, verbose)
+    if not quiet:
+        msg = 'Transformed CSV written to {output}.'.format(**locals())
+        click.echo(msg)
+    sys.exit(errors_count)
+
+
 ######################################################################
 # Error management
 ######################################################################

src/attributecode/transform.py

@@ -0,0 +1,304 @@
+#!/usr/bin/env python
+# -*- coding: utf8 -*-
+# ============================================================================
+#  Copyright (c) 2013-2018 nexB Inc. http://www.nexb.com/ - All rights reserved.
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#      http://www.apache.org/licenses/LICENSE-2.0
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+# ============================================================================
+
+from __future__ import absolute_import
+from __future__ import print_function
+from __future__ import unicode_literals
+
+from collections import Counter
+from collections import OrderedDict
+import io
+
+import attr
+
+from attributecode import CRITICAL
+from attributecode import Error
+from attributecode import saneyaml
+from attributecode.util import python2
+
+if python2:  # pragma: nocover
+    from itertools import izip_longest as zip_longest  # NOQA
+
+    import backports.csv as csv  # NOQA
+else:  # pragma: nocover
+    from itertools import zip_longest  # NOQA
+
+    import csv  # NOQA
+
+
+def transform_csv_to_csv(location, output, transformer):
+    """
+    Read a CSV file at `location` and write a new CSV file at `output`. Apply
+    transformations using the `transformer` Tranformer.
+    Return a list of Error objects.
+    """
+    if not transformer:
+        raise ValueError('Cannot transform without Transformer')
+
+    rows = read_csv_rows(location)
+
+    column_names, data, errors = transform_data(rows, transformer)
+
+    if errors:
+        return errors
+    else:
+        write_csv(output, data, column_names)
+        return []
+
+
+def transform_data(rows, transformer):
+    """
+    Read a list of list of CSV-like data `rows` and apply transformations using the
+    `transformer` Tranformer.
+    Return a tuple of:
+       ([column names...], [transformed ordered mappings...], [Error objects..])
+    """
+
+    if not transformer:
+        return rows
+
+    errors = []
+    rows = iter(rows)
+    column_names = next(rows)
+    column_names = transformer.clean_columns(column_names)
+
+    dupes = check_duplicate_columns(column_names)
+
+    if dupes:
+        msg = 'Duplicated column name: {name}'
+        errors.extend(Error(CRITICAL, msg.format(name)) for name in dupes)
+        return column_names, [], errors
+
+    column_names = transformer.apply_renamings(column_names)
+
+    # convert to mappings using the renamed columns
+    data = [OrderedDict(zip_longest(column_names, row)) for row in rows]
+
+    if transformer.column_filters:
+        data = list(transformer.filter_columns(data))
+        column_names = [c for c in column_names if c in transformer.column_filters]
+
+    errors = transformer.check_required_columns(data)
+    if errors:
+        return column_names, data, errors
+
+    if transformer.row_filters:
+        data = list(transformer.filter_rows(data))
+
+    return column_names, data, errors
+
+
+tranformer_config_help = '''
+A transform configuration file is used to describe which transformations and
+validations to apply to a source CSV file. This is a simple text file using YAML
+format, using the same format as an .ABOUT file.
+
+The attributes that can be set in a configuration file are:
+
+* column_renamings:
+An optional mapping of source CSV column name to target CSV new column name that
+is used to rename CSV columns.
+
+For instance with this configuration the columns "Directory/Location" will be
+renamed to "about_resource" and "foo" to "bar":
+    renamings:
+        'Directory/Location' : about_resource
+        foo : bar
+
+The renaming is always applied first before other transforms and checks. All
+other column names referenced below are these that exist AFTER the renamings
+have been applied to the existing column names.
+
+* required_columns:
+An optional list of required column names that must have a value, beyond the
+standard columns names. If a source CSV does not have such a column or a row is
+missing a value for a required column, an error is reported.
+
+For instance with this configuration an error will be reported if the columns
+"name" and "version" are missing or if any row does not have a value set for
+these columns:
+    required_columns:
+        - name
+        - version
+
+* column_filters:
+An optional list of column names that should be kept in the transformed CSV. If
+this list is provided, all the columns from the source CSV that should be kept
+in the target CSV must be listed be even if they are standard or required
+columns. If this list is not provided, all source CSV columns are kept in the
+transformed target CSV.
+
+For instance with this configuration the target CSV will only contains the "name"
+and "version" columns and no other column:
+    column_filters:
+        - name
+        - version
+
+* row_filters:
+An optional list of mappings of <column name>: <value> that a source CSV row
+should match to be added to the transformed target CSV. If any column value of a
+row matches any such filter it is kept. Otherwise it is skipped. Filters are
+applied last after all renamings, checks and tranforms and can therefore onlu
+use remaining column names.
+
+For instance with this configuration the target CSV will only contain rows that
+have a "path" equal to "/root/user/lib":
+    row_filters:
+        path : /root/user/lib
+'''
+
+
+@attr.attributes
+class Transformer(object):
+    __doc__ = tranformer_config_help
+
+    column_renamings = attr.attrib(default=attr.Factory(dict))
+    required_columns = attr.attrib(default=attr.Factory(list))
+    column_filters = attr.attrib(default=attr.Factory(list))
+    row_filters = attr.attrib(default=attr.Factory(list))
+
+    # TODO: populate these!
+    # a list of all the standard columns from AboutCode toolkit
+    standard_columns = attr.attrib(default=attr.Factory(list), init=False)
+    # a list of the subset of standard columns that are essential and MUST be
+    # present for AboutCode toolkit to work
+    essential_columns = attr.attrib(default=attr.Factory(list), init=False)
+
+    @classmethod
+    def default(cls):
+        """
+        Return a default Transformer with built-in transforms.
+        """
+        return cls(
+            column_renamings={},
+            required_columns=[],
+            column_filters=[],
+            row_filters=[],
+        )
+
+    @classmethod
+    def from_file(cls, location):
+        """
+        Load and return a Transformer instance from a YAML configuration file at
+        `location`.
+        """
+        with io.open(location, encoding='utf-8') as conf:
+            data = saneyaml.load(conf.read())
+        return cls(
+            column_renamings=data.get('column_renamings', {}),
+            required_columns=data.get('required_columns', []),
+            column_filters=data.get('column_filters', []),
+            row_filters=data.get('row_filters', []),
+        )
+
+    def check_required_columns(self, data):
+        """
+        Return a list of Error for a `data` list of ordered mappings where a
+        mapping is missing a value for a required column name.
+        """
+        errors = []
+        required = set(self.essential_columns + self.required_columns)
+        if not required:
+            return []
+
+        for rn, item in enumerate(data):
+            missings = [rk for rk in required if not item.get(rk)]
+            if not missings:
+                continue
+
+            missings = ', '.join(missings)
+            msg = 'Row {rn} is missing required values for columns: {missings}'
+            errors.append(Error(CRITICAL, msg.format(**locals())))
+        return errors
+
+    def apply_renamings(self, column_names):
+        """
+        Return a tranformed list of `column_names` where columns are renamed
+        based on this Transformer configuration.
+        """
+        renamings = self.column_renamings
+        if not renamings:
+            return column_names
+        renamings = {n.lower(): rn.lower() for n, rn in renamings.items()}
+
+        renamed = []
+        for name in column_names:
+            name = name.lower()
+            new_name = renamings.get(name, name)
+            renamed.append(new_name)
+        return renamed
+
+    def clean_columns(self, column_names):
+        """
+        Apply standard cleanups to a list of columns and return these.
+        """
+        if not column_names:
+            return column_names
+        return [c.strip().lower() for c in column_names]
+
+    def filter_columns(self, data):
+        """
+        Yield transformed mappings from a `data` list of mappings keeping only
+        columns with a name in the `column_filters`of this Transformer.
+        Return the data unchanged if no `column_filters` exists.
+        """
+        column_filters = set(self.clean_columns(self.column_filters))
+        for entry in data:
+            items = ((k, v) for k, v in entry.items() if k in column_filters)
+            yield OrderedDict(items)
+
+    def filter_rows(self, data):
+        """
+        Yield a filtered list of mappings from a `data` list of mappings keeping
+        only items that match any one of the `row_filters` of this Transformer.
+        Return the data unchanged if no `row_filters` is avilable in this
+        Transformer.
+        """
+        filters = self.row_filters
+        for entry in data:
+            for filt in filters:
+                for filtered_column_name, filtered_column_value in filt.items():
+                    if entry.get(filtered_column_name) == filtered_column_value:
+                        yield entry
+
+
+def check_duplicate_columns(column_names):
+    """
+    Check that there are no duplicate in the `column_names` list of column name
+    strings, ignoring case. Return a list of unique duplicated column names.
+    """
+    counted = Counter(c.lower() for c in column_names)
+    return [column for column, count in sorted(counted.items()) if count > 1]
+
+
+def read_csv_rows(location):
+    """
+    Yield rows (as a list of values) from a CSV file at `location`.
+    """
+    with io.open(location, encoding='utf-8') as csvfile:
+        reader = csv.reader(csvfile)
+        for row in reader:
+            yield row
+
+
+def write_csv(location, data, column_names):  # NOQA
+    """
+    Write a CSV file at `location` the `data` list of ordered mappings using the
+    `column_names`.
+    """
+    with io.open(location, 'w', encoding='utf-8') as csvfile:
+        writer = csv.DictWriter(csvfile, fieldnames=column_names)
+        writer.writeheader()
+        writer.writerows(data)