Handle colons in section name

README.md

@@ -134,8 +134,8 @@ EOF
 A VRPLIB instance contains problem **specifications** and problem **data**. 
 - Specifications are key-value pairs separated by a colon. In the example above, `NAME` and `EDGE_WEIGHT_TYPE` are the two data specifications.
 - Data are explicit array-like values such as customer coordinates or service times. 
-Each data section should start with a header name that ends with `_SECTION`, e.g., `NODE_COORD_SECTION` and `SERVICE_TIME_SECTION`. It is then followed by rows of values and each row must start with an index representing the depot or customer. 
-There are two exceptions: values in `EDGE_WEIGHT_SECTION` and `DEPOT_SECTION` should not start with an index.
+Each data section should start with a header name that ends with `_SECTION`, e.g., `NODE_COORD_SECTION` and `SERVICE_TIME_SECTION`. Section names may also end with a colon, e.g., `DEMAND_SECTION:`. The name must be followed by rows of values and each row must start with an index representing the depot or customer. 
+There are two exceptions to this rule: values in `EDGE_WEIGHT_SECTION` and `DEPOT_SECTION` should not start with an index.
 
 Besides the rules outlined above, `vrplib` is not strict about the naming of specifications or sections. 
 This means that you can use `vrplib` to read VRPLIB instances with custom specifications like `MY_SPECIFICATION: SOME_VALUE` and custom section names like `MY_SECTION`.

tests/parse/test_parse_vrplib.py

@@ -1,4 +1,5 @@
 from pathlib import Path
+from textwrap import dedent
 
 import numpy as np
 from numpy.testing import assert_, assert_equal, assert_raises
@@ -275,3 +276,30 @@ def test_empty_text():
     """
     actual = parse_vrplib("")
     assert_equal(actual, {})
+
+
+def test_section_with_colon():
+    """
+    Tests if a section name containing a colon is parsed correctly.
+    See https://github.com/PyVRP/VRPLIB/issues/132 for details.
+    """
+    instance = dedent(
+        """
+        DIMENSION: 1
+        EDGE_WEIGHT_TYPE: EXACT_2D
+        NODE_COORD_SECTION:
+        1 1 1
+        DEMAND_SECTION :
+        1 10
+        DEPOT_SECTION
+        1
+        EOF
+        """
+    )
+
+    result = parse_vrplib(instance)  # should not raise
+    assert_equal(result["dimension"], 1)
+    assert_equal(result["edge_weight_type"], "EXACT_2D")
+    assert_equal(result["demand"], [10])
+    assert_equal(result["node_coord"], [[1, 1]])
+    assert_equal(result["depot"], [0])

vrplib/parse/parse_vrplib.py

@@ -71,14 +71,12 @@ def group_specifications_and_sections(lines: list[str]):
         if idx < end_section:  # Skip all lines of the current section
             continue
 
-        if ":" in line:
-            specs.append(line)
-        elif "_SECTION" in line:
-            start = lines.index(line)
+        if "_SECTION" in line:
+            start = idx
             end_section = start + 1
 
             for next_line in lines[start + 1 :]:
-                if ":" in next_line:
+                if ":" in next_line and "_SECTION" not in next_line:
                     raise ValueError("Specification presented after section.")
 
                 # The current section ends when a next section or an EOF token
@@ -89,6 +87,8 @@ def group_specifications_and_sections(lines: list[str]):
                 end_section += 1
 
             sections.append(lines[start:end_section])
+        elif ":" in line:
+            specs.append(line)
         else:
             msg = "Instance does not conform to the VRPLIB format."
             raise RuntimeError(msg)
@@ -111,7 +111,8 @@ def parse_section(
     """
     Parses the data section lines.
     """
-    name = lines[0].strip().removesuffix("_SECTION").lower()
+    # Some section names include colons, so we strip those as well.
+    name = lines[0].strip(" :").removesuffix("_SECTION").lower()
     rows = [[infer_type(n) for n in line.split()] for line in lines[1:]]
 
     if name == "edge_weight":