[io.ascii.cds] Fix reading of multi-line CDS descriptions where the continued line starts with a number

astropy/io/ascii/cds.py

@@ -15,7 +15,7 @@
 import re
 from contextlib import suppress
 
-from astropy.units import Unit
+from astropy.units import Unit, UnitsWarning, UnrecognizedUnit
 
 from . import core, fixedwidth
 
@@ -130,11 +130,30 @@
                 if unit == "---":
                     col.unit = None  # "---" is the marker for no unit in CDS/MRT table
                 else:
-                    col.unit = Unit(unit, format="cds", parse_strict="warn")
+                    try:
+                        col.unit = Unit(unit, format="cds", parse_strict="warn")
+                    except UnitsWarning:
+                        # catch when warnings are turned into errors so we can check
+                        # whether this line is likely a multi-line description (see below)
+                        col.unit = UnrecognizedUnit(unit)
                 col.description = (match.group("descr") or "").strip()
                 col.raw_type = match.group("format")
-                col.type = self.get_col_type(col)
-
+                try:
+                    col.type = self.get_col_type(col)
+                except ValueError:
+                    # If parsing the format fails and the unit is unrecognized,
+                    # then this line is likely a continuation of the previous col's
+                    # description that happens to start with a number
+                    if isinstance(col.unit, UnrecognizedUnit):
+                        if len(cols[-1].description) > 0:
+                            cols[-1].description += " "
+                        cols[-1].description += line.strip()
+                        continue
+                else:
+                    if col.unit is not None:
+                        # Because we may have ignored a UnitsWarning turned into an error
+                        # we do this again so it can be raised again if it is a real error
+                        col.unit = Unit(unit, format="cds", parse_strict="warn")
                 match = re.match(
                     # Matches limits specifier (eg []) that may or may not be
                     # present
@@ -173,6 +192,8 @@
                 cols.append(col)
             else:  # could be a continuation of the previous col's description
                 if cols:
+                    if len(cols[-1].description) > 0:
+                        cols[-1].description += " "
                     cols[-1].description += line.strip()
                 else:
                     raise ValueError(f'Line "{line}" not parsable as CDS header')

astropy/io/ascii/tests/data/cds/description/ReadMe

@@ -54,7 +54,8 @@ Byte-by-byte Description of file: table.dat
       24  I1    ---       ion       ?=0
                                     - Ionization stage (1 for neutral element)
   26- 30  F5.2  eV        chiEx     Excitation potential
-  32- 37  F6.2  ---       loggf     Logarithm of the oscillator strength
+  32- 37  F6.2  ---       loggf     log10 of the gf value - logarithm base
+                                    10 of stat. weight times oscillator strength 
   39- 43  F5.1  0.1pm     EW        ?=-9.9 Equivalent width (in mA)
   46- 49  F4.1  0.1pm   e_EW        ?=-9.9 rms uncertainty on EW
   51- 56  F6.3  ---       Q         ?=-9.999 DAOSPEC quality parameter Q

astropy/io/ascii/tests/test_cds_header_from_readme.py

@@ -37,14 +37,19 @@ def test_description():
         assert_equal(len(table), 2)
         assert_equal(table["Cluster"].description, "Cluster name")
         assert_equal(table["Star"].description, "")
-        assert_equal(table["Wave"].description, "wave? Wavelength in Angstroms")
+        assert_equal(table["Wave"].description, "wave ? Wavelength in Angstroms")
         assert_equal(table["El"].description, "a")
         assert_equal(
             table["ion"].description, "- Ionization stage (1 for neutral element)"
         )
+        assert_equal(
+            table["loggf"].description,
+            "log10 of the gf value - logarithm base 10 of stat. weight times "
+            "oscillator strength",
+        )
         assert_equal(table["EW"].description, "Equivalent width (in mA)")
         assert_equal(
-            table["Q"].description, "DAOSPEC quality parameter Q(large values are bad)"
+            table["Q"].description, "DAOSPEC quality parameter Q (large values are bad)"
         )
 
 
@@ -229,7 +234,7 @@ def test_cds_no_whitespace():
     assert_equal(r.header.cols[7].null, "-9.9")
     assert_equal(
         r.header.cols[10].description,
-        "DAOSPEC quality parameter Q(large values are bad)",
+        "DAOSPEC quality parameter Q (large values are bad)",
     )
     assert_equal(r.header.cols[10].null, "-9.999")
 

docs/changes/io.ascii/15617.bugfix.rst

@@ -0,0 +1 @@
+Reading of CDS header files with multi-line descriptions where the continued line started with a number was broken. This is now fixed.