1	#!/usr/bin/env bash
2
3	#### Lazy Evaluation of Alternative
4	i=0
5	x=x
6	echo ${x:-$((i++))}
7	echo $i
8	echo ${undefined:-$((i++))}
9	echo $i # i is one because the alternative was only evaluated once
10	## status: 0
11	## stdout-json: "x\n0\n0\n1\n"
12	## N-I dash status: 2
13	## N-I dash stdout-json: "x\n0\n"
14
15	#### Default value when empty
16	empty=''
17	echo ${empty:-is empty}
18	## stdout: is empty
19
20	#### Default value when unset
21	echo ${unset-is unset}
22	## stdout: is unset
23
24	#### Unquoted with array as default value
25	set -- '1 2' '3 4'
26	argv.py X${unset=x"$@"x}X
27	## stdout: ['Xx1', '2', '3', '4xX']
28
29	#### Quoted with array as default value
30	set -- '1 2' '3 4'
31	argv.py "X${unset=x"$@"x}X"
32	## stdout: ['Xx1 2 3 4xX']
33	## BUG bash stdout: ['Xx1', '2', '3', '4xX']
34
35	#### Assign default with array
36	# HMMMM osh stdout-json: "['Xx1 2', '3 4xX']\n['x1 2 3 4x']\n"
37	# I think OSH diverges here because VTest is different than VOp1?
38	# I parse all the arg words the same way.
39	set -- '1 2' '3 4'
40	argv.py X${unset=x"$@"x}X
41	argv.py "$unset"
42	## STDOUT:
43	['Xx1', '2', '3', '4xX']
44	['x1 2 3 4x']
45	## #END
46
47	#### Assign default value when empty
48	empty=''
49	${empty:=is empty}
50	echo $empty
51	## stdout: is empty
52
53	#### Assign default value when unset
54	${unset=is unset}
55	echo $unset
56	## stdout: is unset
57
58	#### Alternative value when empty
59	v=foo
60	empty=''
61	echo ${v:+v is not empty} ${empty:+is not empty}
62	## stdout: v is not empty
63
64	#### Alternative value when unset
65	v=foo
66	echo ${v+v is not unset} ${unset:+is not unset}
67	## stdout: v is not unset
68
69	#### Error when empty
70	empty=''
71	echo ${empty:?'is em'pty} # test eval of error
72	echo should not get here
73	## stdout-json: ""
74	## status: 1
75	## OK dash status: 2
76
77	#### Error when unset
78	echo ${unset?is empty}
79	echo should not get here
80	## stdout-json: ""
81	## status: 1
82	## OK dash status: 2
83
84	#### Error when unset
85	v=foo
86	echo ${v+v is not unset} ${unset:+is not unset}
87	## stdout: v is not unset