Update vendored copy of pkgdb_to_bzl.py

* add `package_configuration.py` module

package_configuration.py

@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+
+import collections
+import types
+
+def unfold_fields(lines):
+    """Unfold fields that were split over multiple lines.
+
+    Returns:
+        A list of strings. Each string represents one field (a name/value pair
+        separated by a colon).
+
+    >>> unfold_fields("foo  \n   bar  \n   baz  \nbiz   \nboz   ")
+    ['foo     bar     baz  ', 'biz   ', 'boz   ']
+    """
+    fields = []
+    for line in lines:
+        if line.startswith(" "):
+            fields[-1] += line
+        elif line.strip():
+            fields.append(line)
+    return fields
+
+PackageConfiguration = collections.namedtuple("PackageConfiguration", [
+    "name",
+    "version",
+    "id",
+    "include_dirs",
+    "library_dirs",
+    "dynamic_library_dirs",
+    "hs_libraries",
+    "depends",
+    "ld_options",
+    "extra_libraries",
+    "haddock_interfaces",
+    "haddock_html",
+])
+
+def parse_package_configuration(lines):
+    """Parses a single package configuration.
+
+    Returns:
+      An instance of `PackageConfiguration`.
+    """
+    pkg = types.SimpleNamespace(
+        include_dirs = [],
+        library_dirs = [],
+        dynamic_library_dirs = [],
+        depends = [],
+        hs_libraries = [],
+        ld_options = [],
+        extra_libraries = [],
+        haddock_interfaces = [],
+        haddock_html = None,
+    )
+    for field in unfold_fields(lines):
+        key, value = field.split(":", 1)
+        value = value.strip()
+        if key == "name":
+            pkg.name = value
+        elif key == "version":
+            pkg.version = value
+        elif key == "id":
+            pkg.id = value
+        elif key == "include-dirs":
+            pkg.include_dirs += value.split()
+        elif key == "library-dirs":
+            pkg.library_dirs += value.split()
+        elif key == "dynamic-library-dirs":
+            pkg.dynamic_library_dirs += value.split()
+        elif key == "hs-libraries":
+            pkg.hs_libraries += value.split()
+        elif key == "depends":
+            pkg.depends += value.split()
+        elif key == "ld-options":
+            pkg.ld_options += [opt.strip('"') for opt in value.split()]
+        elif key == "extra-libraries":
+            pkg.extra_libraries += value.split()
+        elif key == "haddock-interfaces":
+            pkg.haddock_interfaces += value.split()
+        elif key == "haddock-html":
+            pkg.haddock_html = value
+
+    return PackageConfiguration(**pkg.__dict__)
+
+def split_records(lines):
+    """Iterator over lists of lines separated by `---`.
+
+    Skips empty records.
+    """
+    separator = "---"
+    record = []
+    for line in lines:
+        if line.rstrip() == separator:
+            yield record
+            record = []
+        else:
+            record.append(line)
+    if record:
+        yield record
+
+def parse_package_database_dump(lines):
+    """Parse the output of ghc-pkg dump.
+
+    Assumes that records are separated by `---`.
+
+    Returns:
+      Iterable of `PackageConfiguration`.
+    """
+    return (
+        parse_package_configuration(record)
+        for record in split_records(lines)
+    )