summaryrefslogtreecommitdiffstats
path: root/bitbake/lib/bb/pysh/pyshyacc.py
blob: e8e80aac45d0c1174ee5748df7063871da3d851c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
# pyshyacc.py - PLY grammar definition for pysh
#
# Copyright 2007 Patrick Mezard
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

"""PLY grammar file.
"""
import os.path
import sys

import pyshlex
tokens = pyshlex.tokens

from ply import yacc
import sherrors
    
class IORedirect:
    def __init__(self, op, filename, io_number=None):
        self.op = op
        self.filename = filename
        self.io_number = io_number
        
class HereDocument:
    def __init__(self, op, name, content, io_number=None):
        self.op = op
        self.name = name
        self.content = content
        self.io_number = io_number

def make_io_redirect(p):
    """Make an IORedirect instance from the input 'io_redirect' production."""
    name, io_number, io_target = p
    assert name=='io_redirect'
    
    if io_target[0]=='io_file':
        io_type, io_op, io_file = io_target
        return IORedirect(io_op, io_file, io_number)
    elif io_target[0]=='io_here':
        io_type, io_op, io_name, io_content = io_target
        return HereDocument(io_op, io_name, io_content, io_number)
    else:
        assert False, "Invalid IO redirection token %s" % repr(io_type)
        
class SimpleCommand:
    """
    assigns contains (name, value) pairs.
    """
    def __init__(self, words, redirs, assigns):
        self.words = list(words)
        self.redirs = list(redirs)
        self.assigns = list(assigns)

class Pipeline:
    def __init__(self, commands, reverse_status=False):
        self.commands = list(commands)
        assert self.commands    #Grammar forbids this
        self.reverse_status = reverse_status
        
class AndOr:
    def __init__(self, op, left, right):
        self.op = str(op)
        self.left = left
        self.right = right
        
class ForLoop:
    def __init__(self, name, items, cmds):
        self.name = str(name)
        self.items = list(items)
        self.cmds = list(cmds)
        
class WhileLoop:
    def __init__(self, condition, cmds):
        self.condition = list(condition)
        self.cmds = list(cmds)
        
class UntilLoop:
    def __init__(self, condition, cmds):
        self.condition = list(condition)
        self.cmds = list(cmds)

class FunDef:
    def __init__(self, name, body):
        self.name = str(name)
        self.body = body
        
class BraceGroup:
    def __init__(self, cmds):
        self.cmds = list(cmds)
        
class IfCond:
    def __init__(self, cond, if_cmds, else_cmds):
        self.cond = list(cond)
        self.if_cmds = if_cmds
        self.else_cmds = else_cmds

class Case:
    def __init__(self, name, items):
        self.name = name
        self.items = items
        
class SubShell:
    def __init__(self, cmds):
        self.cmds = cmds

class RedirectList:
    def __init__(self, cmd, redirs):
        self.cmd = cmd
        self.redirs = list(redirs)
        
def get_production(productions, ptype):
    """productions must be a list of production tuples like (name, obj) where
    name is the production string identifier.
    Return the first production named 'ptype'. Raise KeyError if None can be
    found.
    """
    for production in productions:
        if production is not None and production[0]==ptype:
            return production
    raise KeyError(ptype)
    
#-------------------------------------------------------------------------------
# PLY grammar definition
#-------------------------------------------------------------------------------

def p_multiple_commands(p):
    """multiple_commands : newline_sequence
                         | complete_command
                         | multiple_commands complete_command"""
    if len(p)==2:
        if p[1] is not None:
            p[0] = [p[1]]
        else:
            p[0] = []
    else:
        p[0] = p[1] + [p[2]]

def p_complete_command(p):
    """complete_command : list separator
                        | list"""
    if len(p)==3 and p[2] and p[2][1] == '&':
        p[0] = ('async', p[1])
    else:
        p[0] = p[1]
                 
def p_list(p):
    """list : list separator_op and_or
            |                   and_or"""
    if len(p)==2:
        p[0] = [p[1]]
    else:
        #if p[2]!=';':
        #    raise NotImplementedError('AND-OR list asynchronous execution is not implemented')
        p[0] = p[1] + [p[3]]
       
def p_and_or(p):
    """and_or : pipeline
              | and_or AND_IF linebreak pipeline
              | and_or OR_IF  linebreak pipeline"""
    if len(p)==2:
        p[0] = p[1]
    else:
        p[0] = ('and_or', AndOr(p[2], p[1], p[4]))
        
def p_maybe_bang_word(p):
    """maybe_bang_word : Bang"""
    p[0] = ('maybe_bang_word', p[1])
            
def p_pipeline(p):
    """pipeline : pipe_sequence
                | bang_word pipe_sequence"""
    if len(p)==3:
        p[0] = ('pipeline', Pipeline(p[2][1:], True))
    else:
        p[0] = ('pipeline', Pipeline(p[1][1:]))

def p_pipe_sequence(p):
    """pipe_sequence : command
                     | pipe_sequence PIPE linebreak command"""
    if len(p)==2:
        p[0] = ['pipe_sequence', p[1]]
    else:
        p[0] = p[1] + [p[4]]

def p_command(p):
    """command : simple_command
               | compound_command
               | compound_command redirect_list
               | function_definition"""
        
    if p[1][0] in ( 'simple_command', 
                    'for_clause',
                    'while_clause',
                    'until_clause',
                    'case_clause',
                    'if_clause',
                    'function_definition',
                    'subshell',
                    'brace_group',):
        if len(p) == 2:
            p[0] = p[1]
        else:
            p[0] = ('redirect_list', RedirectList(p[1], p[2][1:]))
    else:
        raise NotImplementedError('%s command is not implemented' % repr(p[1][0]))

def p_compound_command(p):
    """compound_command : brace_group
                        | subshell
                        | for_clause
                        | case_clause
                        | if_clause
                        | while_clause
                        | until_clause"""
    p[0] = p[1]

def p_subshell(p):
    """subshell : LPARENS compound_list RPARENS"""
    p[0] = ('subshell', SubShell(p[2][1:]))

def p_compound_list(p):
    """compound_list : term
                     | newline_list term
                     |              term separator
                     | newline_list term separator"""
    productions = p[1:]           
    try:
        sep = get_production(productions, 'separator')
        if sep[1]!=';':
            raise NotImplementedError()
    except KeyError:
        pass
    term = get_production(productions, 'term')
    p[0] = ['compound_list'] + term[1:]

def p_term(p):
    """term : term separator and_or
            |                and_or"""
    if len(p)==2:
        p[0] = ['term', p[1]]
    else:
        if p[2] is not None and p[2][1] == '&':
            p[0] = ['term', ('async', p[1][1:])] + [p[3]]
        else:
            p[0] = p[1] + [p[3]]
            
def p_maybe_for_word(p):
    # Rearrange 'For' priority wrt TOKEN. See p_for_word
    """maybe_for_word : For"""
    p[0] = ('maybe_for_word', p[1])

def p_for_clause(p):
    """for_clause : for_word name linebreak                            do_group
                  | for_word name linebreak in          sequential_sep do_group
                  | for_word name linebreak in wordlist sequential_sep do_group"""
    productions = p[1:]
    do_group = get_production(productions, 'do_group')
    try:
        items = get_production(productions, 'in')[1:]
    except KeyError:
        raise NotImplementedError('"in" omission is not implemented')
        
    try:
        items = get_production(productions, 'wordlist')[1:]
    except KeyError:
        items = []
        
    name = p[2]
    p[0] = ('for_clause', ForLoop(name, items, do_group[1:]))

def p_name(p):
    """name : token""" #Was NAME instead of token
    p[0] = p[1]

def p_in(p):
    """in : In"""
    p[0] = ('in', p[1])

def p_wordlist(p):
    """wordlist : wordlist token
                |          token"""
    if len(p)==2:
        p[0] = ['wordlist', ('TOKEN', p[1])]
    else:
        p[0] = p[1] + [('TOKEN', p[2])]

def p_case_clause(p):
    """case_clause : Case token linebreak in linebreak case_list    Esac
                   | Case token linebreak in linebreak case_list_ns Esac
                   | Case token linebreak in linebreak              Esac"""
    if len(p) < 8:
        items = []
    else:
        items = p[6][1:]
    name = p[2]
    p[0] = ('case_clause', Case(name, [c[1] for c in items]))
       
def p_case_list_ns(p):
    """case_list_ns : case_list case_item_ns
                    |           case_item_ns"""
    p_case_list(p)
      
def p_case_list(p):
    """case_list : case_list case_item
                 |           case_item"""
    if len(p)==2:
        p[0] = ['case_list', p[1]]
    else:
        p[0] = p[1] + [p[2]]
        
def p_case_item_ns(p):
    """case_item_ns :         pattern RPARENS               linebreak
                    |         pattern RPARENS compound_list linebreak
                    | LPARENS pattern RPARENS               linebreak
                    | LPARENS pattern RPARENS compound_list linebreak"""
    p_case_item(p)
                 
def p_case_item(p):
    """case_item :         pattern RPARENS linebreak     DSEMI linebreak
                 |         pattern RPARENS compound_list DSEMI linebreak
                 | LPARENS pattern RPARENS linebreak     DSEMI linebreak
                 | LPARENS pattern RPARENS compound_list DSEMI linebreak"""
    if len(p) < 7:
        name = p[1][1:]
    else:
        name = p[2][1:]

    try:
        cmds = get_production(p[1:], "compound_list")[1:]
    except KeyError:
        cmds = []

    p[0] = ('case_item', (name, cmds))
                 
def p_pattern(p):
    """pattern :              token
               | pattern PIPE token"""
    if len(p)==2:
        p[0] = ['pattern', ('TOKEN', p[1])]
    else:
        p[0] = p[1] + [('TOKEN', p[2])]

def p_maybe_if_word(p):
    # Rearrange 'If' priority wrt TOKEN. See p_if_word
    """maybe_if_word : If"""
    p[0] = ('maybe_if_word', p[1])

def p_maybe_then_word(p):
    # Rearrange 'Then' priority wrt TOKEN. See p_then_word
    """maybe_then_word : Then"""
    p[0] = ('maybe_then_word', p[1])
                 
def p_if_clause(p):
    """if_clause : if_word compound_list then_word compound_list else_part Fi
                 | if_word compound_list then_word compound_list           Fi"""
    else_part = []
    if len(p)==7:
        else_part = p[5]
    p[0] = ('if_clause', IfCond(p[2][1:], p[4][1:], else_part))
                 
def p_else_part(p):
    """else_part : Elif compound_list then_word compound_list else_part
                 | Elif compound_list then_word compound_list
                 | Else compound_list"""
    if len(p)==3:
        p[0] = p[2][1:]
    else:
        else_part = []
        if len(p)==6:
            else_part = p[5]
        p[0] = ('elif', IfCond(p[2][1:], p[4][1:], else_part))
                 
def p_while_clause(p):
    """while_clause : While compound_list do_group"""
    p[0] = ('while_clause', WhileLoop(p[2][1:], p[3][1:]))
    
def p_maybe_until_word(p):
    # Rearrange 'Until' priority wrt TOKEN. See p_until_word
    """maybe_until_word : Until"""
    p[0] = ('maybe_until_word', p[1])
           
def p_until_clause(p):
    """until_clause : until_word compound_list do_group"""
    p[0] = ('until_clause', UntilLoop(p[2][1:], p[3][1:]))
                 
def p_function_definition(p):
    """function_definition : fname LPARENS RPARENS linebreak function_body"""
    p[0] = ('function_definition', FunDef(p[1], p[5]))
                 
def p_function_body(p):
    """function_body : compound_command
                     | compound_command redirect_list"""
    if len(p)!=2:
        raise NotImplementedError('functions redirections lists are not implemented')    
    p[0] = p[1]    

def p_fname(p):
    """fname : TOKEN""" #Was NAME instead of token
    p[0] = p[1]

def p_brace_group(p):
    """brace_group : Lbrace compound_list Rbrace"""
    p[0] = ('brace_group', BraceGroup(p[2][1:]))

def p_maybe_done_word(p):
    #See p_assignment_word for details.
    """maybe_done_word : Done"""
    p[0] = ('maybe_done_word', p[1])

def p_maybe_do_word(p):
    """maybe_do_word : Do"""
    p[0] = ('maybe_do_word', p[1])

def p_do_group(p):
    """do_group : do_word compound_list done_word"""
    #Do group contains a list of AndOr
    p[0] = ['do_group'] + p[2][1:]

def p_simple_command(p):
    """simple_command : cmd_prefix cmd_word cmd_suffix
                      | cmd_prefix cmd_word
                      | cmd_prefix
                      | cmd_name cmd_suffix
                      | cmd_name"""
    words, redirs, assigns = [], [], []
    for e in p[1:]:
        name = e[0]
        if name in ('cmd_prefix', 'cmd_suffix'):
            for sube in e[1:]:
                subname = sube[0]
                if subname=='io_redirect':
                    redirs.append(make_io_redirect(sube))
                elif subname=='ASSIGNMENT_WORD':
                    assigns.append(sube)
                else:
                    words.append(sube)
        elif name in ('cmd_word', 'cmd_name'):
            words.append(e)
            
    cmd = SimpleCommand(words, redirs, assigns)
    p[0] = ('simple_command', cmd)

def p_cmd_name(p):
    """cmd_name : TOKEN"""
    p[0] = ('cmd_name', p[1])
    
def p_cmd_word(p):
    """cmd_word : token"""
    p[0] = ('cmd_word', p[1])

def p_maybe_assignment_word(p):
    #See p_assignment_word for details.
    """maybe_assignment_word : ASSIGNMENT_WORD"""
    p[0] = ('maybe_assignment_word', p[1])
    
def p_cmd_prefix(p):
    """cmd_prefix :            io_redirect
                  | cmd_prefix io_redirect
                  |            assignment_word
                  | cmd_prefix assignment_word"""
    try:
        prefix = get_production(p[1:], 'cmd_prefix')
    except KeyError:
        prefix = ['cmd_prefix']
        
    try:
        value = get_production(p[1:], 'assignment_word')[1]
        value = ('ASSIGNMENT_WORD', value.split('=', 1))
    except KeyError:        
        value = get_production(p[1:], 'io_redirect')
    p[0] = prefix + [value]
                                  
def p_cmd_suffix(p):
    """cmd_suffix   :            io_redirect
                    | cmd_suffix io_redirect
                    |            token
                    | cmd_suffix token
                    |            maybe_for_word
                    | cmd_suffix maybe_for_word
                    |            maybe_done_word
                    | cmd_suffix maybe_done_word
                    |            maybe_do_word
                    | cmd_suffix maybe_do_word
                    |            maybe_until_word
                    | cmd_suffix maybe_until_word
                    |            maybe_assignment_word
                    | cmd_suffix maybe_assignment_word
                    |            maybe_if_word
                    | cmd_suffix maybe_if_word
                    |            maybe_then_word
                    | cmd_suffix maybe_then_word
                    |            maybe_bang_word
                    | cmd_suffix maybe_bang_word"""
    try:
        suffix = get_production(p[1:], 'cmd_suffix')
        token = p[2]
    except KeyError:
        suffix = ['cmd_suffix']
        token = p[1]
        
    if isinstance(token, tuple):
        if token[0]=='io_redirect':
            p[0] = suffix + [token]
        else:
            #Convert maybe_*  to TOKEN if necessary
            p[0] = suffix + [('TOKEN', token[1])]
    else:
        p[0] = suffix + [('TOKEN', token)]
                 
def p_redirect_list(p):
    """redirect_list : io_redirect
                     | redirect_list io_redirect"""
    if len(p) == 2:
        p[0] = ['redirect_list', make_io_redirect(p[1])]
    else:
        p[0] = p[1] + [make_io_redirect(p[2])]
    
def p_io_redirect(p):
    """io_redirect :           io_file
                   | IO_NUMBER io_file
                   |           io_here
                   | IO_NUMBER io_here"""
    if len(p)==3:
        p[0] = ('io_redirect', p[1], p[2])
    else:
        p[0] = ('io_redirect', None, p[1])
    
def p_io_file(p):
    #Return the tuple (operator, filename)
    """io_file : LESS      filename
               | LESSAND   filename
               | GREATER   filename
               | GREATAND  filename
               | DGREAT    filename
               | LESSGREAT filename
               | CLOBBER   filename"""
    #Extract the filename from the file
    p[0] = ('io_file', p[1], p[2][1])

def p_filename(p):
    #Return the filename
    """filename : TOKEN"""
    p[0] = ('filename', p[1])
        
def p_io_here(p):
    """io_here : DLESS here_end
               | DLESSDASH here_end"""
    p[0] = ('io_here', p[1], p[2][1], p[2][2])

def p_here_end(p):
    """here_end : HERENAME TOKEN"""
    p[0] = ('here_document', p[1], p[2])
    
def p_newline_sequence(p):
    # Nothing in the grammar can handle leading NEWLINE productions, so add
    # this one with the lowest possible priority relatively to newline_list.
    """newline_sequence : newline_list"""
    p[0] = None
    
def p_newline_list(p):
    """newline_list : NEWLINE
                    | newline_list NEWLINE"""
    p[0] = None
                    
def p_linebreak(p):
    """linebreak : newline_list
                 | empty"""
    p[0] = None

def p_separator_op(p):                 
    """separator_op : COMMA
                    | AMP"""
    p[0] = p[1]

def p_separator(p):
    """separator : separator_op linebreak
                 | newline_list"""
    if len(p)==2:
        #Ignore newlines
        p[0] = None
    else:
        #Keep the separator operator
        p[0] = ('separator', p[1])
                 
def p_sequential_sep(p):
    """sequential_sep : COMMA linebreak
                      | newline_list"""
    p[0] = None

# Low priority TOKEN => for_word conversion.
# Let maybe_for_word be used as a token when necessary in higher priority
# rules. 
def p_for_word(p):
    """for_word : maybe_for_word"""
    p[0] = p[1]

def p_if_word(p):
    """if_word : maybe_if_word"""
    p[0] = p[1]

def p_then_word(p):
    """then_word : maybe_then_word"""
    p[0] = p[1]

def p_done_word(p):
    """done_word : maybe_done_word"""
    p[0] = p[1]

def p_do_word(p):
    """do_word : maybe_do_word"""
    p[0] = p[1]
    
def p_until_word(p):
    """until_word : maybe_until_word"""
    p[0] = p[1]
    
def p_assignment_word(p):
    """assignment_word : maybe_assignment_word"""
    p[0] = ('assignment_word', p[1][1])
    
def p_bang_word(p):
    """bang_word : maybe_bang_word"""
    p[0] = ('bang_word', p[1][1])

def p_token(p):
    """token : TOKEN
             | Fi"""
    p[0] = p[1]

def p_empty(p):
    'empty :'
    p[0] = None
    
# Error rule for syntax errors
def p_error(p):
    msg = []
    w = msg.append
    w('%r\n' % p)
    w('followed by:\n')
    for i in range(5):
        n = yacc.token()
        if not n:
            break
        w('  %r\n' % n)
    raise sherrors.ShellSyntaxError(''.join(msg))

# Build the parser
try:
    import pyshtables
except ImportError:
    outputdir = os.path.dirname(__file__)
    if not os.access(outputdir, os.W_OK):
        outputdir = ''
    yacc.yacc(tabmodule = 'pyshtables', outputdir = outputdir, debug = 0)
else:
    yacc.yacc(tabmodule = 'pysh.pyshtables', write_tables = 0, debug = 0)


def parse(input, eof=False, debug=False):
    """Parse a whole script at once and return the generated AST and unconsumed
    data in a tuple.
    
    NOTE: eof is probably meaningless for now, the parser being unable to work
    in pull mode. It should be set to True.
    """
    lexer = pyshlex.PLYLexer()
    remaining = lexer.add(input, eof)
    if lexer.is_empty():
        return [], remaining
    if debug:
        debug = 2
    return yacc.parse(lexer=lexer, debug=debug), remaining

#-------------------------------------------------------------------------------
# AST rendering helpers
#-------------------------------------------------------------------------------    

def format_commands(v):
    """Return a tree made of strings and lists. Make command trees easier to
    display.
    """
    if isinstance(v, list):
        return [format_commands(c) for c in v]
    if isinstance(v, tuple):
        if len(v)==2 and isinstance(v[0], str) and not isinstance(v[1], str):
            if v[0] == 'async':
                return ['AsyncList', map(format_commands, v[1])]
            else:
                #Avoid decomposing tuples like ('pipeline', Pipeline(...))
                return format_commands(v[1])
        return format_commands(list(v))
    elif isinstance(v, IfCond):
        name = ['IfCond']
        name += ['if', map(format_commands, v.cond)]
        name += ['then', map(format_commands, v.if_cmds)]
        name += ['else', map(format_commands, v.else_cmds)]
        return name
    elif isinstance(v, ForLoop):
        name = ['ForLoop']
        name += [repr(v.name)+' in ', map(str, v.items)]
        name += ['commands', map(format_commands, v.cmds)]
        return name
    elif isinstance(v, AndOr):
        return [v.op, format_commands(v.left), format_commands(v.right)]
    elif isinstance(v, Pipeline):
        name = 'Pipeline'
        if v.reverse_status:
            name = '!' + name
        return [name, format_commands(v.commands)]
    elif isinstance(v, Case):
        name = ['Case']
        name += [v.name, format_commands(v.items)]
    elif isinstance(v, SimpleCommand):
        name = ['SimpleCommand']
        if v.words:                
            name += ['words', map(str, v.words)]
        if v.assigns:
            assigns = [tuple(a[1]) for a in v.assigns]
            name += ['assigns', map(str, assigns)]
        if v.redirs:
            name += ['redirs', map(format_commands, v.redirs)]
        return name
    elif isinstance(v, RedirectList):
        name = ['RedirectList']
        if v.redirs:
            name += ['redirs', map(format_commands, v.redirs)]
        name += ['command', format_commands(v.cmd)]
        return name
    elif isinstance(v, IORedirect):
        return ' '.join(map(str, (v.io_number, v.op, v.filename)))
    elif isinstance(v, HereDocument):
        return ' '.join(map(str, (v.io_number, v.op, repr(v.name), repr(v.content))))
    elif isinstance(v, SubShell):
        return ['SubShell', map(format_commands, v.cmds)]
    else:
        return repr(v)
             
def print_commands(cmds, output=sys.stdout):
    """Pretty print a command tree."""
    def print_tree(cmd, spaces, output):
        if isinstance(cmd, list):
            for c in cmd:
                print_tree(c, spaces + 3, output)              
        else:
            print >>output, ' '*spaces + str(cmd)
    
    formatted = format_commands(cmds)
    print_tree(formatted, 0, output)
    
    
def stringify_commands(cmds): 
    """Serialize a command tree as a string.
    
    Returned string is not pretty and is currently used for unit tests only.
    """   
    def stringify(value):
        output = []
        if isinstance(value, list):
            formatted = []
            for v in value:
                formatted.append(stringify(v))
            formatted = ' '.join(formatted)
            output.append(''.join(['<', formatted, '>']))
        else:
            output.append(value)
        return ' '.join(output)
            
    return stringify(format_commands(cmds))
    
        
def visit_commands(cmds, callable):
    """Visit the command tree and execute callable on every Pipeline and 
    SimpleCommand instances.
    """
    if isinstance(cmds, (tuple, list)):
        map(lambda c: visit_commands(c,callable), cmds)
    elif isinstance(cmds, (Pipeline, SimpleCommand)):
        callable(cmds)