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Source file src/regexp/syntax/parse_test.go

Documentation: regexp/syntax

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package syntax
     6  
     7  import (
     8  	"fmt"
     9  	"strings"
    10  	"testing"
    11  	"unicode"
    12  )
    13  
    14  type parseTest struct {
    15  	Regexp string
    16  	Dump   string
    17  }
    18  
    19  var parseTests = []parseTest{
    20  	// Base cases
    21  	{`a`, `lit{a}`},
    22  	{`a.`, `cat{lit{a}dot{}}`},
    23  	{`a.b`, `cat{lit{a}dot{}lit{b}}`},
    24  	{`ab`, `str{ab}`},
    25  	{`a.b.c`, `cat{lit{a}dot{}lit{b}dot{}lit{c}}`},
    26  	{`abc`, `str{abc}`},
    27  	{`a|^`, `alt{lit{a}bol{}}`},
    28  	{`a|b`, `cc{0x61-0x62}`},
    29  	{`(a)`, `cap{lit{a}}`},
    30  	{`(a)|b`, `alt{cap{lit{a}}lit{b}}`},
    31  	{`a*`, `star{lit{a}}`},
    32  	{`a+`, `plus{lit{a}}`},
    33  	{`a?`, `que{lit{a}}`},
    34  	{`a{2}`, `rep{2,2 lit{a}}`},
    35  	{`a{2,3}`, `rep{2,3 lit{a}}`},
    36  	{`a{2,}`, `rep{2,-1 lit{a}}`},
    37  	{`a*?`, `nstar{lit{a}}`},
    38  	{`a+?`, `nplus{lit{a}}`},
    39  	{`a??`, `nque{lit{a}}`},
    40  	{`a{2}?`, `nrep{2,2 lit{a}}`},
    41  	{`a{2,3}?`, `nrep{2,3 lit{a}}`},
    42  	{`a{2,}?`, `nrep{2,-1 lit{a}}`},
    43  	// Malformed { } are treated as literals.
    44  	{`x{1001`, `str{x{1001}`},
    45  	{`x{9876543210`, `str{x{9876543210}`},
    46  	{`x{9876543210,`, `str{x{9876543210,}`},
    47  	{`x{2,1`, `str{x{2,1}`},
    48  	{`x{1,9876543210`, `str{x{1,9876543210}`},
    49  	{``, `emp{}`},
    50  	{`|`, `emp{}`}, // alt{emp{}emp{}} but got factored
    51  	{`|x|`, `alt{emp{}lit{x}emp{}}`},
    52  	{`.`, `dot{}`},
    53  	{`^`, `bol{}`},
    54  	{`$`, `eol{}`},
    55  	{`\|`, `lit{|}`},
    56  	{`\(`, `lit{(}`},
    57  	{`\)`, `lit{)}`},
    58  	{`\*`, `lit{*}`},
    59  	{`\+`, `lit{+}`},
    60  	{`\?`, `lit{?}`},
    61  	{`{`, `lit{{}`},
    62  	{`}`, `lit{}}`},
    63  	{`\.`, `lit{.}`},
    64  	{`\^`, `lit{^}`},
    65  	{`\$`, `lit{$}`},
    66  	{`\\`, `lit{\}`},
    67  	{`[ace]`, `cc{0x61 0x63 0x65}`},
    68  	{`[abc]`, `cc{0x61-0x63}`},
    69  	{`[a-z]`, `cc{0x61-0x7a}`},
    70  	{`[a]`, `lit{a}`},
    71  	{`\-`, `lit{-}`},
    72  	{`-`, `lit{-}`},
    73  	{`\_`, `lit{_}`},
    74  	{`abc`, `str{abc}`},
    75  	{`abc|def`, `alt{str{abc}str{def}}`},
    76  	{`abc|def|ghi`, `alt{str{abc}str{def}str{ghi}}`},
    77  
    78  	// Posix and Perl extensions
    79  	{`[[:lower:]]`, `cc{0x61-0x7a}`},
    80  	{`[a-z]`, `cc{0x61-0x7a}`},
    81  	{`[^[:lower:]]`, `cc{0x0-0x60 0x7b-0x10ffff}`},
    82  	{`[[:^lower:]]`, `cc{0x0-0x60 0x7b-0x10ffff}`},
    83  	{`(?i)[[:lower:]]`, `cc{0x41-0x5a 0x61-0x7a 0x17f 0x212a}`},
    84  	{`(?i)[a-z]`, `cc{0x41-0x5a 0x61-0x7a 0x17f 0x212a}`},
    85  	{`(?i)[^[:lower:]]`, `cc{0x0-0x40 0x5b-0x60 0x7b-0x17e 0x180-0x2129 0x212b-0x10ffff}`},
    86  	{`(?i)[[:^lower:]]`, `cc{0x0-0x40 0x5b-0x60 0x7b-0x17e 0x180-0x2129 0x212b-0x10ffff}`},
    87  	{`\d`, `cc{0x30-0x39}`},
    88  	{`\D`, `cc{0x0-0x2f 0x3a-0x10ffff}`},
    89  	{`\s`, `cc{0x9-0xa 0xc-0xd 0x20}`},
    90  	{`\S`, `cc{0x0-0x8 0xb 0xe-0x1f 0x21-0x10ffff}`},
    91  	{`\w`, `cc{0x30-0x39 0x41-0x5a 0x5f 0x61-0x7a}`},
    92  	{`\W`, `cc{0x0-0x2f 0x3a-0x40 0x5b-0x5e 0x60 0x7b-0x10ffff}`},
    93  	{`(?i)\w`, `cc{0x30-0x39 0x41-0x5a 0x5f 0x61-0x7a 0x17f 0x212a}`},
    94  	{`(?i)\W`, `cc{0x0-0x2f 0x3a-0x40 0x5b-0x5e 0x60 0x7b-0x17e 0x180-0x2129 0x212b-0x10ffff}`},
    95  	{`[^\\]`, `cc{0x0-0x5b 0x5d-0x10ffff}`},
    96  	//	{ `\C`, `byte{}` },  // probably never
    97  
    98  	// Unicode, negatives, and a double negative.
    99  	{`\p{Braille}`, `cc{0x2800-0x28ff}`},
   100  	{`\P{Braille}`, `cc{0x0-0x27ff 0x2900-0x10ffff}`},
   101  	{`\p{^Braille}`, `cc{0x0-0x27ff 0x2900-0x10ffff}`},
   102  	{`\P{^Braille}`, `cc{0x2800-0x28ff}`},
   103  	{`\pZ`, `cc{0x20 0xa0 0x1680 0x2000-0x200a 0x2028-0x2029 0x202f 0x205f 0x3000}`},
   104  	{`[\p{Braille}]`, `cc{0x2800-0x28ff}`},
   105  	{`[\P{Braille}]`, `cc{0x0-0x27ff 0x2900-0x10ffff}`},
   106  	{`[\p{^Braille}]`, `cc{0x0-0x27ff 0x2900-0x10ffff}`},
   107  	{`[\P{^Braille}]`, `cc{0x2800-0x28ff}`},
   108  	{`[\pZ]`, `cc{0x20 0xa0 0x1680 0x2000-0x200a 0x2028-0x2029 0x202f 0x205f 0x3000}`},
   109  	{`\p{Lu}`, mkCharClass(unicode.IsUpper)},
   110  	{`[\p{Lu}]`, mkCharClass(unicode.IsUpper)},
   111  	{`(?i)[\p{Lu}]`, mkCharClass(isUpperFold)},
   112  	{`\p{Any}`, `dot{}`},
   113  	{`\p{^Any}`, `cc{}`},
   114  
   115  	// Hex, octal.
   116  	{`[\012-\234]\141`, `cat{cc{0xa-0x9c}lit{a}}`},
   117  	{`[\x{41}-\x7a]\x61`, `cat{cc{0x41-0x7a}lit{a}}`},
   118  
   119  	// More interesting regular expressions.
   120  	{`a{,2}`, `str{a{,2}}`},
   121  	{`\.\^\$\\`, `str{.^$\}`},
   122  	{`[a-zABC]`, `cc{0x41-0x43 0x61-0x7a}`},
   123  	{`[^a]`, `cc{0x0-0x60 0x62-0x10ffff}`},
   124  	{`[α-ε☺]`, `cc{0x3b1-0x3b5 0x263a}`}, // utf-8
   125  	{`a*{`, `cat{star{lit{a}}lit{{}}`},
   126  
   127  	// Test precedences
   128  	{`(?:ab)*`, `star{str{ab}}`},
   129  	{`(ab)*`, `star{cap{str{ab}}}`},
   130  	{`ab|cd`, `alt{str{ab}str{cd}}`},
   131  	{`a(b|c)d`, `cat{lit{a}cap{cc{0x62-0x63}}lit{d}}`},
   132  
   133  	// Test flattening.
   134  	{`(?:a)`, `lit{a}`},
   135  	{`(?:ab)(?:cd)`, `str{abcd}`},
   136  	{`(?:a+b+)(?:c+d+)`, `cat{plus{lit{a}}plus{lit{b}}plus{lit{c}}plus{lit{d}}}`},
   137  	{`(?:a+|b+)|(?:c+|d+)`, `alt{plus{lit{a}}plus{lit{b}}plus{lit{c}}plus{lit{d}}}`},
   138  	{`(?:a|b)|(?:c|d)`, `cc{0x61-0x64}`},
   139  	{`a|.`, `dot{}`},
   140  	{`.|a`, `dot{}`},
   141  	{`(?:[abc]|A|Z|hello|world)`, `alt{cc{0x41 0x5a 0x61-0x63}str{hello}str{world}}`},
   142  	{`(?:[abc]|A|Z)`, `cc{0x41 0x5a 0x61-0x63}`},
   143  
   144  	// Test Perl quoted literals
   145  	{`\Q+|*?{[\E`, `str{+|*?{[}`},
   146  	{`\Q+\E+`, `plus{lit{+}}`},
   147  	{`\Qab\E+`, `cat{lit{a}plus{lit{b}}}`},
   148  	{`\Q\\E`, `lit{\}`},
   149  	{`\Q\\\E`, `str{\\}`},
   150  
   151  	// Test Perl \A and \z
   152  	{`(?m)^`, `bol{}`},
   153  	{`(?m)$`, `eol{}`},
   154  	{`(?-m)^`, `bot{}`},
   155  	{`(?-m)$`, `eot{}`},
   156  	{`(?m)\A`, `bot{}`},
   157  	{`(?m)\z`, `eot{\z}`},
   158  	{`(?-m)\A`, `bot{}`},
   159  	{`(?-m)\z`, `eot{\z}`},
   160  
   161  	// Test named captures
   162  	{`(?P<name>a)`, `cap{name:lit{a}}`},
   163  
   164  	// Case-folded literals
   165  	{`[Aa]`, `litfold{A}`},
   166  	{`[\x{100}\x{101}]`, `litfold{Ā}`},
   167  	{`[Δδ]`, `litfold{Δ}`},
   168  
   169  	// Strings
   170  	{`abcde`, `str{abcde}`},
   171  	{`[Aa][Bb]cd`, `cat{strfold{AB}str{cd}}`},
   172  
   173  	// Factoring.
   174  	{`abc|abd|aef|bcx|bcy`, `alt{cat{lit{a}alt{cat{lit{b}cc{0x63-0x64}}str{ef}}}cat{str{bc}cc{0x78-0x79}}}`},
   175  	{`ax+y|ax+z|ay+w`, `cat{lit{a}alt{cat{plus{lit{x}}lit{y}}cat{plus{lit{x}}lit{z}}cat{plus{lit{y}}lit{w}}}}`},
   176  
   177  	// Bug fixes.
   178  	{`(?:.)`, `dot{}`},
   179  	{`(?:x|(?:xa))`, `cat{lit{x}alt{emp{}lit{a}}}`},
   180  	{`(?:.|(?:.a))`, `cat{dot{}alt{emp{}lit{a}}}`},
   181  	{`(?:A(?:A|a))`, `cat{lit{A}litfold{A}}`},
   182  	{`(?:A|a)`, `litfold{A}`},
   183  	{`A|(?:A|a)`, `litfold{A}`},
   184  	{`(?s).`, `dot{}`},
   185  	{`(?-s).`, `dnl{}`},
   186  	{`(?:(?:^).)`, `cat{bol{}dot{}}`},
   187  	{`(?-s)(?:(?:^).)`, `cat{bol{}dnl{}}`},
   188  
   189  	// RE2 prefix_tests
   190  	{`abc|abd`, `cat{str{ab}cc{0x63-0x64}}`},
   191  	{`a(?:b)c|abd`, `cat{str{ab}cc{0x63-0x64}}`},
   192  	{`abc|abd|aef|bcx|bcy`,
   193  		`alt{cat{lit{a}alt{cat{lit{b}cc{0x63-0x64}}str{ef}}}` +
   194  			`cat{str{bc}cc{0x78-0x79}}}`},
   195  	{`abc|x|abd`, `alt{str{abc}lit{x}str{abd}}`},
   196  	{`(?i)abc|ABD`, `cat{strfold{AB}cc{0x43-0x44 0x63-0x64}}`},
   197  	{`[ab]c|[ab]d`, `cat{cc{0x61-0x62}cc{0x63-0x64}}`},
   198  	{`.c|.d`, `cat{dot{}cc{0x63-0x64}}`},
   199  	{`x{2}|x{2}[0-9]`,
   200  		`cat{rep{2,2 lit{x}}alt{emp{}cc{0x30-0x39}}}`},
   201  	{`x{2}y|x{2}[0-9]y`,
   202  		`cat{rep{2,2 lit{x}}alt{lit{y}cat{cc{0x30-0x39}lit{y}}}}`},
   203  	{`a.*?c|a.*?b`,
   204  		`cat{lit{a}alt{cat{nstar{dot{}}lit{c}}cat{nstar{dot{}}lit{b}}}}`},
   205  
   206  	// Valid repetitions.
   207  	{`((((((((((x{2}){2}){2}){2}){2}){2}){2}){2}){2}))`, ``},
   208  	{`((((((((((x{1}){2}){2}){2}){2}){2}){2}){2}){2}){2})`, ``},
   209  }
   210  
   211  const testFlags = MatchNL | PerlX | UnicodeGroups
   212  
   213  func TestParseSimple(t *testing.T) {
   214  	testParseDump(t, parseTests, testFlags)
   215  }
   216  
   217  var foldcaseTests = []parseTest{
   218  	{`AbCdE`, `strfold{ABCDE}`},
   219  	{`[Aa]`, `litfold{A}`},
   220  	{`a`, `litfold{A}`},
   221  
   222  	// 0x17F is an old English long s (looks like an f) and folds to s.
   223  	// 0x212A is the Kelvin symbol and folds to k.
   224  	{`A[F-g]`, `cat{litfold{A}cc{0x41-0x7a 0x17f 0x212a}}`}, // [Aa][A-z...]
   225  	{`[[:upper:]]`, `cc{0x41-0x5a 0x61-0x7a 0x17f 0x212a}`},
   226  	{`[[:lower:]]`, `cc{0x41-0x5a 0x61-0x7a 0x17f 0x212a}`},
   227  }
   228  
   229  func TestParseFoldCase(t *testing.T) {
   230  	testParseDump(t, foldcaseTests, FoldCase)
   231  }
   232  
   233  var literalTests = []parseTest{
   234  	{"(|)^$.[*+?]{5,10},\\", "str{(|)^$.[*+?]{5,10},\\}"},
   235  }
   236  
   237  func TestParseLiteral(t *testing.T) {
   238  	testParseDump(t, literalTests, Literal)
   239  }
   240  
   241  var matchnlTests = []parseTest{
   242  	{`.`, `dot{}`},
   243  	{"\n", "lit{\n}"},
   244  	{`[^a]`, `cc{0x0-0x60 0x62-0x10ffff}`},
   245  	{`[a\n]`, `cc{0xa 0x61}`},
   246  }
   247  
   248  func TestParseMatchNL(t *testing.T) {
   249  	testParseDump(t, matchnlTests, MatchNL)
   250  }
   251  
   252  var nomatchnlTests = []parseTest{
   253  	{`.`, `dnl{}`},
   254  	{"\n", "lit{\n}"},
   255  	{`[^a]`, `cc{0x0-0x9 0xb-0x60 0x62-0x10ffff}`},
   256  	{`[a\n]`, `cc{0xa 0x61}`},
   257  }
   258  
   259  func TestParseNoMatchNL(t *testing.T) {
   260  	testParseDump(t, nomatchnlTests, 0)
   261  }
   262  
   263  // Test Parse -> Dump.
   264  func testParseDump(t *testing.T, tests []parseTest, flags Flags) {
   265  	for _, tt := range tests {
   266  		re, err := Parse(tt.Regexp, flags)
   267  		if err != nil {
   268  			t.Errorf("Parse(%#q): %v", tt.Regexp, err)
   269  			continue
   270  		}
   271  		if tt.Dump == "" {
   272  			// It parsed. That's all we care about.
   273  			continue
   274  		}
   275  		d := dump(re)
   276  		if d != tt.Dump {
   277  			t.Errorf("Parse(%#q).Dump() = %#q want %#q", tt.Regexp, d, tt.Dump)
   278  		}
   279  	}
   280  }
   281  
   282  // dump prints a string representation of the regexp showing
   283  // the structure explicitly.
   284  func dump(re *Regexp) string {
   285  	var b strings.Builder
   286  	dumpRegexp(&b, re)
   287  	return b.String()
   288  }
   289  
   290  var opNames = []string{
   291  	OpNoMatch:        "no",
   292  	OpEmptyMatch:     "emp",
   293  	OpLiteral:        "lit",
   294  	OpCharClass:      "cc",
   295  	OpAnyCharNotNL:   "dnl",
   296  	OpAnyChar:        "dot",
   297  	OpBeginLine:      "bol",
   298  	OpEndLine:        "eol",
   299  	OpBeginText:      "bot",
   300  	OpEndText:        "eot",
   301  	OpWordBoundary:   "wb",
   302  	OpNoWordBoundary: "nwb",
   303  	OpCapture:        "cap",
   304  	OpStar:           "star",
   305  	OpPlus:           "plus",
   306  	OpQuest:          "que",
   307  	OpRepeat:         "rep",
   308  	OpConcat:         "cat",
   309  	OpAlternate:      "alt",
   310  }
   311  
   312  // dumpRegexp writes an encoding of the syntax tree for the regexp re to b.
   313  // It is used during testing to distinguish between parses that might print
   314  // the same using re's String method.
   315  func dumpRegexp(b *strings.Builder, re *Regexp) {
   316  	if int(re.Op) >= len(opNames) || opNames[re.Op] == "" {
   317  		fmt.Fprintf(b, "op%d", re.Op)
   318  	} else {
   319  		switch re.Op {
   320  		default:
   321  			b.WriteString(opNames[re.Op])
   322  		case OpStar, OpPlus, OpQuest, OpRepeat:
   323  			if re.Flags&NonGreedy != 0 {
   324  				b.WriteByte('n')
   325  			}
   326  			b.WriteString(opNames[re.Op])
   327  		case OpLiteral:
   328  			if len(re.Rune) > 1 {
   329  				b.WriteString("str")
   330  			} else {
   331  				b.WriteString("lit")
   332  			}
   333  			if re.Flags&FoldCase != 0 {
   334  				for _, r := range re.Rune {
   335  					if unicode.SimpleFold(r) != r {
   336  						b.WriteString("fold")
   337  						break
   338  					}
   339  				}
   340  			}
   341  		}
   342  	}
   343  	b.WriteByte('{')
   344  	switch re.Op {
   345  	case OpEndText:
   346  		if re.Flags&WasDollar == 0 {
   347  			b.WriteString(`\z`)
   348  		}
   349  	case OpLiteral:
   350  		for _, r := range re.Rune {
   351  			b.WriteRune(r)
   352  		}
   353  	case OpConcat, OpAlternate:
   354  		for _, sub := range re.Sub {
   355  			dumpRegexp(b, sub)
   356  		}
   357  	case OpStar, OpPlus, OpQuest:
   358  		dumpRegexp(b, re.Sub[0])
   359  	case OpRepeat:
   360  		fmt.Fprintf(b, "%d,%d ", re.Min, re.Max)
   361  		dumpRegexp(b, re.Sub[0])
   362  	case OpCapture:
   363  		if re.Name != "" {
   364  			b.WriteString(re.Name)
   365  			b.WriteByte(':')
   366  		}
   367  		dumpRegexp(b, re.Sub[0])
   368  	case OpCharClass:
   369  		sep := ""
   370  		for i := 0; i < len(re.Rune); i += 2 {
   371  			b.WriteString(sep)
   372  			sep = " "
   373  			lo, hi := re.Rune[i], re.Rune[i+1]
   374  			if lo == hi {
   375  				fmt.Fprintf(b, "%#x", lo)
   376  			} else {
   377  				fmt.Fprintf(b, "%#x-%#x", lo, hi)
   378  			}
   379  		}
   380  	}
   381  	b.WriteByte('}')
   382  }
   383  
   384  func mkCharClass(f func(rune) bool) string {
   385  	re := &Regexp{Op: OpCharClass}
   386  	lo := rune(-1)
   387  	for i := rune(0); i <= unicode.MaxRune; i++ {
   388  		if f(i) {
   389  			if lo < 0 {
   390  				lo = i
   391  			}
   392  		} else {
   393  			if lo >= 0 {
   394  				re.Rune = append(re.Rune, lo, i-1)
   395  				lo = -1
   396  			}
   397  		}
   398  	}
   399  	if lo >= 0 {
   400  		re.Rune = append(re.Rune, lo, unicode.MaxRune)
   401  	}
   402  	return dump(re)
   403  }
   404  
   405  func isUpperFold(r rune) bool {
   406  	if unicode.IsUpper(r) {
   407  		return true
   408  	}
   409  	c := unicode.SimpleFold(r)
   410  	for c != r {
   411  		if unicode.IsUpper(c) {
   412  			return true
   413  		}
   414  		c = unicode.SimpleFold(c)
   415  	}
   416  	return false
   417  }
   418  
   419  func TestFoldConstants(t *testing.T) {
   420  	last := rune(-1)
   421  	for i := rune(0); i <= unicode.MaxRune; i++ {
   422  		if unicode.SimpleFold(i) == i {
   423  			continue
   424  		}
   425  		if last == -1 && minFold != i {
   426  			t.Errorf("minFold=%#U should be %#U", minFold, i)
   427  		}
   428  		last = i
   429  	}
   430  	if maxFold != last {
   431  		t.Errorf("maxFold=%#U should be %#U", maxFold, last)
   432  	}
   433  }
   434  
   435  func TestAppendRangeCollapse(t *testing.T) {
   436  	// AppendRange should collapse each of the new ranges
   437  	// into the earlier ones (it looks back two ranges), so that
   438  	// the slice never grows very large.
   439  	// Note that we are not calling cleanClass.
   440  	var r []rune
   441  	for i := rune('A'); i <= 'Z'; i++ {
   442  		r = appendRange(r, i, i)
   443  		r = appendRange(r, i+'a'-'A', i+'a'-'A')
   444  	}
   445  	if string(r) != "AZaz" {
   446  		t.Errorf("appendRange interlaced A-Z a-z = %s, want AZaz", string(r))
   447  	}
   448  }
   449  
   450  var invalidRegexps = []string{
   451  	`(`,
   452  	`)`,
   453  	`(a`,
   454  	`a)`,
   455  	`(a))`,
   456  	`(a|b|`,
   457  	`a|b|)`,
   458  	`(a|b|))`,
   459  	`(a|b`,
   460  	`a|b)`,
   461  	`(a|b))`,
   462  	`[a-z`,
   463  	`([a-z)`,
   464  	`[a-z)`,
   465  	`([a-z]))`,
   466  	`x{1001}`,
   467  	`x{9876543210}`,
   468  	`x{2,1}`,
   469  	`x{1,9876543210}`,
   470  	"\xff", // Invalid UTF-8
   471  	"[\xff]",
   472  	"[\\\xff]",
   473  	"\\\xff",
   474  	`(?P<name>a`,
   475  	`(?P<name>`,
   476  	`(?P<name`,
   477  	`(?P<x y>a)`,
   478  	`(?P<>a)`,
   479  	`[a-Z]`,
   480  	`(?i)[a-Z]`,
   481  	`a{100000}`,
   482  	`a{100000,}`,
   483  	"((((((((((x{2}){2}){2}){2}){2}){2}){2}){2}){2}){2})",
   484  	`\Q\E*`,
   485  }
   486  
   487  var onlyPerl = []string{
   488  	`[a-b-c]`,
   489  	`\Qabc\E`,
   490  	`\Q*+?{[\E`,
   491  	`\Q\\E`,
   492  	`\Q\\\E`,
   493  	`\Q\\\\E`,
   494  	`\Q\\\\\E`,
   495  	`(?:a)`,
   496  	`(?P<name>a)`,
   497  }
   498  
   499  var onlyPOSIX = []string{
   500  	"a++",
   501  	"a**",
   502  	"a?*",
   503  	"a+*",
   504  	"a{1}*",
   505  	".{1}{2}.{3}",
   506  }
   507  
   508  func TestParseInvalidRegexps(t *testing.T) {
   509  	for _, regexp := range invalidRegexps {
   510  		if re, err := Parse(regexp, Perl); err == nil {
   511  			t.Errorf("Parse(%#q, Perl) = %s, should have failed", regexp, dump(re))
   512  		}
   513  		if re, err := Parse(regexp, POSIX); err == nil {
   514  			t.Errorf("Parse(%#q, POSIX) = %s, should have failed", regexp, dump(re))
   515  		}
   516  	}
   517  	for _, regexp := range onlyPerl {
   518  		if _, err := Parse(regexp, Perl); err != nil {
   519  			t.Errorf("Parse(%#q, Perl): %v", regexp, err)
   520  		}
   521  		if re, err := Parse(regexp, POSIX); err == nil {
   522  			t.Errorf("Parse(%#q, POSIX) = %s, should have failed", regexp, dump(re))
   523  		}
   524  	}
   525  	for _, regexp := range onlyPOSIX {
   526  		if re, err := Parse(regexp, Perl); err == nil {
   527  			t.Errorf("Parse(%#q, Perl) = %s, should have failed", regexp, dump(re))
   528  		}
   529  		if _, err := Parse(regexp, POSIX); err != nil {
   530  			t.Errorf("Parse(%#q, POSIX): %v", regexp, err)
   531  		}
   532  	}
   533  }
   534  
   535  func TestToStringEquivalentParse(t *testing.T) {
   536  	for _, tt := range parseTests {
   537  		re, err := Parse(tt.Regexp, testFlags)
   538  		if err != nil {
   539  			t.Errorf("Parse(%#q): %v", tt.Regexp, err)
   540  			continue
   541  		}
   542  		if tt.Dump == "" {
   543  			// It parsed. That's all we care about.
   544  			continue
   545  		}
   546  		d := dump(re)
   547  		if d != tt.Dump {
   548  			t.Errorf("Parse(%#q).Dump() = %#q want %#q", tt.Regexp, d, tt.Dump)
   549  			continue
   550  		}
   551  
   552  		s := re.String()
   553  		if s != tt.Regexp {
   554  			// If ToString didn't return the original regexp,
   555  			// it must have found one with fewer parens.
   556  			// Unfortunately we can't check the length here, because
   557  			// ToString produces "\\{" for a literal brace,
   558  			// but "{" is a shorter equivalent in some contexts.
   559  			nre, err := Parse(s, testFlags)
   560  			if err != nil {
   561  				t.Errorf("Parse(%#q.String() = %#q): %v", tt.Regexp, s, err)
   562  				continue
   563  			}
   564  			nd := dump(nre)
   565  			if d != nd {
   566  				t.Errorf("Parse(%#q) -> %#q; %#q vs %#q", tt.Regexp, s, d, nd)
   567  			}
   568  
   569  			ns := nre.String()
   570  			if s != ns {
   571  				t.Errorf("Parse(%#q) -> %#q -> %#q", tt.Regexp, s, ns)
   572  			}
   573  		}
   574  	}
   575  }
   576  

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