EDTF demo/validation notebook

src/undate/__init__.py

@@ -1 +1,6 @@
 __version__ = "0.3.0.dev0"
+
+from undate.date import DatePrecision
+from undate.undate import Undate, UndateInterval
+
+__all__ = ["Undate", "UndateInterval", "DatePrecision"]

src/undate/converters/edtf/converter.py

@@ -71,8 +71,14 @@ def _undate_to_string(self, undate: Undate) -> str:
         if undate.precision >= DatePrecision.YEAR:
             year = self._convert_missing_digits(undate.year, undate.MISSING_DIGIT)
             # years with more than 4 digits should be prefixed with Y
-            if year and len(year) > 4:
-                year = f"Y{year}"
+            # (don't count minus sign when checking digits)
+            if year and len(year.lstrip("-")) > 4:
+                negative_year = ""
+                if year.startswith("-"):
+                    negative_year = "-"
+                    year = year[1:]
+                year = f"{negative_year}Y{year}"
+
             # TODO: handle uncertain / approximate
             parts.append(year or EDTF_UNSPECIFIED_DIGIT * 4)
 
@@ -97,4 +103,4 @@ def _undate_to_string(self, undate: Undate) -> str:
             return "-".join(parts)
 
         # how can we have an empty string? probably shouldn't get here
-        return ""
+        raise ValueError("Failed to generate an EDTF string from %r", undate)

src/undate/converters/edtf/edtf.lark

@@ -14,7 +14,7 @@
 
 date: year | year "-" month | year "-" month "-" day
 
-year: INT
+year: INT | /\-/ INT
 month: /(0[1-9])|(1[0-2])/
 day: /([0-2][1-9])|(3[0-1])/
 
@@ -34,14 +34,15 @@ uncertain_approximate: "%"
 
 // The character 'X' may be used in place of one or more rightmost
 // digits to indicate that the value of that digit is unspecified
+// In Level 2, year may be completely unspecified.
 unspecified: /X/
-?year_unspecified: /\d+/ unspecified+
+?year_unspecified: /\d+/ unspecified+ | unspecified ~ 4
 ?month_unspecified: "0".."1"? unspecified ~ 1..2
 //?year_month_unspecified: year_l1 "-" month_unspecified
 ?day_unspecified: "0".."3"? unspecified ~ 1..2
 
 // 'Y' may be used at the beginning of the date string to signify that the date is a year, when (and only when) the year exceeds four digits, i.e. for years later than 9999 or earlier than -9999.
-year_fivedigitsplus: /Y\d{5,}/
+year_fivedigitsplus: /-?Y\d{5,}/
 ?year_l1: year_fivedigitsplus | year | year_unspecified
 
 // The values 21, 22, 23, 24 may be used used to signify

src/undate/converters/edtf/transformer.py

@@ -64,8 +64,26 @@ def day_unspecified(self, items):
     def date_level1(self, items):
         return self.date(items)
 
+    def year(self, items):
+        # when the year is negative, there are two tokens
+        if len(items) > 1 and items[0] == "-":
+            # an anonymous token for the - and the integer year
+            year = items[1]
+            return Tree(data="year", children=[-year])
+
+        return Tree(data="year", children=[items[0]])
+
     def year_fivedigitsplus(self, items):
         # strip off the leading Y and convert to integer
         token = items[0]
-        year = int(token.value.lstrip("Y"))
+        value = token.value
+        # check if year is negative
+        negative = False
+        if value.startswith("-"):
+            value = value[1:]
+            negative = True
+        year = int(value.lstrip("Y"))
+
+        if negative:
+            year = -year
         return Tree(data="year", children=[year])

src/undate/undate.py

@@ -58,9 +58,12 @@ def __init__(
         elif year:
             self.precision = DatePrecision.YEAR
 
-        # TODO: refactor partial date min/max calculations
+        # special case: treat year = XXXX as unknown/none
+        if year == "XXXX":
+            year = None
 
         if year is not None:
+            # could we / should we use str.isnumeric here?
             try:
                 year = int(year)
                 # update initial value since it is used to determine
@@ -113,7 +116,7 @@ def __init__(
             # if we have no day or partial day, calculate min / max
             min_day = 1
             # if we know year and month (or max month), calculate exactly
-            if year and month:
+            if year and month and isinstance(year, int):
                 _, max_day = monthrange(int(year), max_month)
             elif year is None and month:
                 # If we don't have year and month,

tests/test_converters/edtf/test_edtf_parser.py

@@ -12,7 +12,10 @@
     "1000-01/2000-05-01",
     # level 1
     "Y170000002",
+    "-Y170000002",
     "2001-21",  # spring 2001
+    # negative year
+    "-1985",
     # qualifiers
     "1984?",
     "2004-06~",
@@ -28,6 +31,12 @@
     "1985-04/..",
     "../1985-04-12",
     "/1985-04-12",
+    # level 2 unspecified digits
+    "156X-12-25",
+    "XXXX-12-XX",
+    "1XXX-12",
+    "1XXX-XX",
+    "1984-1X",
 ]
 
 

tests/test_converters/edtf/test_edtf_transformer.py

@@ -14,6 +14,9 @@
     ("1000-01/2000-05-01", UndateInterval(Undate(1000, 1), Undate(2000, 5, 1))),
     # level 1
     ("Y17000002", Undate(17000002)),
+    ("-Y17000002", Undate(-17000002)),
+    # negative year
+    ("-1985", Undate(-1985)),
     # "2001-21",  # spring 2001
     # qualifiers TODO - not yet supported by undate
     # "1984?",
@@ -30,6 +33,11 @@
     ("1985-04/..", UndateInterval(Undate(1985, 4), None)),
     ("../1985-04-12", UndateInterval(None, Undate(1985, 4, 12))),
     ("/1985-04-12", UndateInterval(None, Undate(1985, 4, 12))),
+    # level 2 unspecified digits
+    ("156X-12-25", Undate("156X", 12, 25)),
+    ("XXXX-12-XX", Undate("XXXX", 12, "XX")),
+    ("1XXX-XX", Undate("1XXX", "XX")),
+    ("1984-1X", Undate(1984, "1X")),
 ]
 
 

tests/test_converters/test_edtf.py

@@ -1,5 +1,6 @@
 import pytest
 from undate.converters.edtf import EDTFDateConverter
+from undate.date import DatePrecision
 from undate.undate import Undate, UndateInterval
 
 
@@ -52,5 +53,12 @@ def test_to_string(self):
 
         assert EDTFDateConverter().to_string(Undate(1991, "0X")) == "1991-0X"
         assert EDTFDateConverter().to_string(Undate(1991, None, 3)) == "1991-XX-03"
+        assert EDTFDateConverter().to_string(Undate(-1984)) == "-1984"
 
+        # if converter can't generate a string for the date,
+        # it should return a value error
+        empty_undate = Undate()
+        empty_undate.precision = DatePrecision.DECADE
+        with pytest.raises(ValueError):
+            EDTFDateConverter().to_string(empty_undate)
         # TODO: override missing digit and confirm replacement