Lint vertical spacing in the code (#3224)

* Lint vertical spacing in the code

* Add some vertical spacing for readability

scripts/lint.py

@@ -0,0 +1,132 @@
+#!/usr/bin/env python
+"""
+Runs custom linting on Rust code.
+"""
+
+import argparse
+import os
+import re
+import sys
+
+
+def lint_file_path(filepath, args) -> int:
+    with open(filepath) as f:
+        lines_in = f.readlines()
+
+    errors, lines_out = lint_lines(filepath, lines_in)
+
+    for error in errors:
+        print(error)
+
+    if args.fix and lines_in != lines_out:
+        with open(filepath, 'w') as f:
+            f.writelines(lines_out)
+        print(f'{filepath} fixed.')
+
+    return len(errors)
+
+
+
+def lint_lines(filepath, lines_in):
+    last_line_was_empty = True
+
+    errors = []
+    lines_out = []
+
+    for line_nr, line in enumerate(lines_in):
+        line_nr = line_nr+1
+
+        # TODO: only # and /// on lines before a keyword
+
+        pattern = r'^\s*((///)|((pub(\(\w*\))? )?((impl|fn|struct|enum|union|trait)\b))).*$'
+        if re.match(pattern, line):
+            if not last_line_was_empty:
+                errors.append(
+                    f'{filepath}:{line_nr}: for readability, add newline before `{line.strip()}`')
+                lines_out.append("\n")
+        lines_out.append(line)
+
+        stripped = line.strip()
+        last_line_was_empty = stripped == '' or \
+            stripped.startswith('#') or \
+            stripped.startswith('//') or \
+            stripped.endswith('{') or \
+            stripped.endswith('(') or \
+            stripped.endswith('\\') or \
+            stripped.endswith('r"') or \
+            stripped.endswith(']')
+
+    return errors, lines_out
+
+
+def test_lint():
+    should_pass = [
+        "hello world",
+        """
+        /// docstring
+        foo
+
+        /// docstring
+        bar
+        """
+    ]
+
+    should_fail = [
+        """
+        /// docstring
+        foo
+        /// docstring
+        bar
+        """
+    ]
+
+    for code in should_pass:
+        errors, _ = lint_lines("test.py", code.split('\n'))
+        assert len(errors) == 0, f'expected this to pass:\n{code}\ngot: {errors}'
+
+    for code in should_fail:
+        errors, _ = lint_lines("test.py", code.split('\n'))
+        assert len(errors) > 0, f'expected this to fail:\n{code}'
+
+    pass
+
+
+def main():
+    test_lint() # Make sure we are bug free before we run!
+
+    parser = argparse.ArgumentParser(
+        description='Lint Rust code with custom linter.')
+    parser.add_argument('files', metavar='file', type=str, nargs='*',
+                        help='File paths. Empty = all files, recursively.')
+    parser.add_argument('--fix', dest='fix', action='store_true',
+                        help='Automatically fix the files')
+
+    args = parser.parse_args()
+
+    num_errors = 0
+
+    if args.files:
+        for filepath in args.files:
+            num_errors += lint_file_path(filepath, args)
+    else:
+        script_dirpath = os.path.dirname(os.path.realpath(__file__))
+        root_dirpath = os.path.abspath(f'{script_dirpath}/..')
+        os.chdir(root_dirpath)
+
+        exclude = set(['target', 'target_ra'])
+        for root, dirs, files in os.walk('.', topdown=True):
+            dirs[:] = [d for d in dirs if d not in exclude]
+            for filename in files:
+                if filename.endswith('.rs'):
+                    filepath = os.path.join(root, filename)
+                    num_errors += lint_file_path(filepath, args)
+
+    if num_errors == 0:
+        print(f"{sys.argv[0]} finished without error")
+        sys.exit(0)
+    else:
+        print(f"{sys.argv[0]} found {num_errors} errors.")
+        sys.exit(1)
+
+if __name__ == '__main__':
+    main()