more error reporting in format.py

2 files changed, 61 insertions, 27 deletions

diff --git a/format.py b/format.py
index e97fac2..d43f835 100755
--- a/format.py
+++ b/format.py
@@ -91,17 +91,18 @@ def default_slice(val, hi, lo):
     >>> default_slice(('label[31:0]', 'imm12'), 11, 0)
     Traceback (most recent call last):
         ...
-    AssertionError: expected 12 bit slice
+    AssertionError: expected 12 bit slice, got label[31:0] (32 bit)
     """
     parsed = subv.parse_reference(val)
     if 'hi' not in parsed:
       parsed['hi'] = hi
       parsed['lo'] = lo
 
+    ref = '{label}[{hi}:{lo}]'.format(**parsed)
+
     p_size = parsed['hi'] - parsed['lo'] + 1
-    assert parsed['size'] == p_size, "expected {} bit slice".format(parsed['size'])
+    assert parsed['size'] == p_size, "expected {} bit slice, got {} ({} bit)".format(parsed['size'], ref, p_size)
 
-    ref = '{label}[{hi}:{lo}]'.format(**parsed)
     return (ref, *val[1:])
 
 def slice_bit_or_ref(val, hi, lo):
@@ -155,7 +156,7 @@ def pack_u(instr):
     >>> pack_u([(0x37, 'lui'), (5, 'rd', 't0'), ('pos[31:0]', 'imm20')])
     Traceback (most recent call last):
         ...
-    AssertionError: expected 20 bit slice
+    AssertionError: expected 20 bit slice, got pos[31:0] (32 bit)
     """
     (op, rd, imm) = instr
     op = bits.u(subv.untag(op), 7)
@@ -283,27 +284,43 @@ instr_map = {
 
 def format(iter):
     segment = None
-    for line in iter:
-        line = subv.parse(line)
-
-        if segment == 'code' and line['type'] == 'instr':
-            op = line['instr'][0]
-            assert len(op) == 2, 'instruction without op label: {}'.format(op)
-
-            (op, label) = op
-            if label not in instr_map:
-                raise ValueError("unknown instruction label: {}".format(label))
-            (formatter, expected) = instr_map[label]
-            if op != expected:
-                raise ValueError("opcode {} doesn't match label {} (expected {})"
-                                 .format(op, label, expected))
-
-            line['instr'] = formatter(line['instr'])
-            yield subv.format(line)
-        else:
-            if line['type'] == 'segment':
-                segment = line['segment'][0]
-            yield line['raw']
+    for line_no, raw_line in enumerate(iter, start=1):
+        try:
+            line = subv.parse(raw_line)
+        except AssertionError as e:
+            message = '''
+failed to format line:
+<input>:{}  {}
+parsed as {}
+            '''.strip().format(line_no, raw_line.strip())
+            raise Exception(message) from e
+
+        try:
+            if segment == 'code' and line['type'] == 'instr':
+                op = line['instr'][0]
+                assert len(op) == 2, 'instruction without op label: {}'.format(op)
+
+                (op, label) = op
+                if label not in instr_map:
+                    raise ValueError("unknown instruction label: {}".format(label))
+                (formatter, expected) = instr_map[label]
+                if op != expected:
+                    raise ValueError("opcode {} doesn't match label {} (expected {})"
+                                     .format(op, label, expected))
+
+                line['instr'] = formatter(line['instr'])
+                yield subv.format(line)
+            else:
+                if line['type'] == 'segment':
+                    segment = line['segment'][0]
+                yield line['raw']
+        except AssertionError as e:
+            message = '''
+failed to format line:
+<input>:{}  {}
+parsed as {}
+            '''.strip().format(line_no, raw_line.strip(), subv.dump(line))
+            raise Exception(message) from e
 
 if __name__ == '__main__':
     import sys
diff --git a/subv.py b/subv.py
index 107f0e9..43bfa35 100644
--- a/subv.py
+++ b/subv.py
@@ -223,12 +223,16 @@ def untag(part, expect=None):
     return part[0]
 
 def format_part(part):
-    """ oppposite of parse_part.
+    """ opposite of parse_part.
 
     >>> format_part((0,))
     '00'
     >>> format_part((0x00,))
     '00'
+    >>> format_part((16,))
+    '10'
+    >>> format_part((0x10,))
+    '10'
 
     >>> format_part(('label', 'tag*'))
     'label/tag*'
@@ -245,7 +249,7 @@ def format_part(part):
     return '/'.join([str(p) for p in part])
 
 def format(line):
-    """ oppposite of parse.
+    """ opposite of parse.
 
     >>> format({
     ...     'type': 'instr',
@@ -262,6 +266,19 @@ def format(line):
     else:
       raise NotImplementedError()
 
+def dump(line):
+    """ debug-friendly string representation of parsed lines.
+
+    >>> dump({
+    ...     'type': 'instr',
+    ...     'instr': [(255, 'op'), (0, 'subop', 'add'), (1, 'rd', 'x1'), ('label[11:0]', 'imm12')],
+    ...     'comment': "this does things."
+    ... })
+    "instr[(255, 'op'), (0, 'subop', 'add'), (1, 'rd', 'x1'), ('label[11:0]', 'imm12')]"
+    """
+
+    return '{}{}'.format(line['type'], line[line['type']])
+
 def join_all(gen):
     res = '\n'.join(gen)
     return res