error_test.go

Documentation: go/parser

     1  // Copyright 2012 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  // This file implements a parser test harness. The files in the testdata
     6  // directory are parsed and the errors reported are compared against the
     7  // error messages expected in the test files. The test files must end in
     8  // .src rather than .go so that they are not disturbed by gofmt runs.
     9  //
    10  // Expected errors are indicated in the test files by putting a comment
    11  // of the form /* ERROR "rx" */ immediately following an offending token.
    12  // The harness will verify that an error matching the regular expression
    13  // rx is reported at that source position.
    14  //
    15  // For instance, the following test file indicates that a "not declared"
    16  // error should be reported for the undeclared variable x:
    17  //
    18  //	package p
    19  //	func f() {
    20  //		_ = x /* ERROR "not declared" */ + 1
    21  //	}
    22  
    23  package parser
    24  
    25  import (
    26  	"go/internal/typeparams"
    27  	"go/scanner"
    28  	"go/token"
    29  	"os"
    30  	"path/filepath"
    31  	"regexp"
    32  	"strings"
    33  	"testing"
    34  )
    35  
    36  const testdata = "testdata"
    37  
    38  // getFile assumes that each filename occurs at most once
    39  func getFile(fset *token.FileSet, filename string) (file *token.File) {
    40  	fset.Iterate(func(f *token.File) bool {
    41  		if f.Name() == filename {
    42  			if file != nil {
    43  				panic(filename + " used multiple times")
    44  			}
    45  			file = f
    46  		}
    47  		return true
    48  	})
    49  	return file
    50  }
    51  
    52  func getPos(fset *token.FileSet, filename string, offset int) token.Pos {
    53  	if f := getFile(fset, filename); f != nil {
    54  		return f.Pos(offset)
    55  	}
    56  	return token.NoPos
    57  }
    58  
    59  // ERROR comments must be of the form /* ERROR "rx" */ and rx is
    60  // a regular expression that matches the expected error message.
    61  // The special form /* ERROR HERE "rx" */ must be used for error
    62  // messages that appear immediately after a token, rather than at
    63  // a token's position.
    64  //
    65  var errRx = regexp.MustCompile(`^/\* *ERROR *(HERE)? *"([^"]*)" *\*/$`)
    66  
    67  // expectedErrors collects the regular expressions of ERROR comments found
    68  // in files and returns them as a map of error positions to error messages.
    69  //
    70  func expectedErrors(fset *token.FileSet, filename string, src []byte) map[token.Pos]string {
    71  	errors := make(map[token.Pos]string)
    72  
    73  	var s scanner.Scanner
    74  	// file was parsed already - do not add it again to the file
    75  	// set otherwise the position information returned here will
    76  	// not match the position information collected by the parser
    77  	s.Init(getFile(fset, filename), src, nil, scanner.ScanComments)
    78  	var prev token.Pos // position of last non-comment, non-semicolon token
    79  	var here token.Pos // position immediately after the token at position prev
    80  
    81  	for {
    82  		pos, tok, lit := s.Scan()
    83  		switch tok {
    84  		case token.EOF:
    85  			return errors
    86  		case token.COMMENT:
    87  			s := errRx.FindStringSubmatch(lit)
    88  			if len(s) == 3 {
    89  				pos := prev
    90  				if s[1] == "HERE" {
    91  					pos = here
    92  				}
    93  				errors[pos] = s[2]
    94  			}
    95  		case token.SEMICOLON:
    96  			// don't use the position of auto-inserted (invisible) semicolons
    97  			if lit != ";" {
    98  				break
    99  			}
   100  			fallthrough
   101  		default:
   102  			prev = pos
   103  			var l int // token length
   104  			if tok.IsLiteral() {
   105  				l = len(lit)
   106  			} else {
   107  				l = len(tok.String())
   108  			}
   109  			here = prev + token.Pos(l)
   110  		}
   111  	}
   112  }
   113  
   114  // compareErrors compares the map of expected error messages with the list
   115  // of found errors and reports discrepancies.
   116  //
   117  func compareErrors(t *testing.T, fset *token.FileSet, expected map[token.Pos]string, found scanner.ErrorList) {
   118  	t.Helper()
   119  	for _, error := range found {
   120  		// error.Pos is a token.Position, but we want
   121  		// a token.Pos so we can do a map lookup
   122  		pos := getPos(fset, error.Pos.Filename, error.Pos.Offset)
   123  		if msg, found := expected[pos]; found {
   124  			// we expect a message at pos; check if it matches
   125  			rx, err := regexp.Compile(msg)
   126  			if err != nil {
   127  				t.Errorf("%s: %v", error.Pos, err)
   128  				continue
   129  			}
   130  			if match := rx.MatchString(error.Msg); !match {
   131  				t.Errorf("%s: %q does not match %q", error.Pos, error.Msg, msg)
   132  				continue
   133  			}
   134  			// we have a match - eliminate this error
   135  			delete(expected, pos)
   136  		} else {
   137  			// To keep in mind when analyzing failed test output:
   138  			// If the same error position occurs multiple times in errors,
   139  			// this message will be triggered (because the first error at
   140  			// the position removes this position from the expected errors).
   141  			t.Errorf("%s: unexpected error: %s", error.Pos, error.Msg)
   142  		}
   143  	}
   144  
   145  	// there should be no expected errors left
   146  	if len(expected) > 0 {
   147  		t.Errorf("%d errors not reported:", len(expected))
   148  		for pos, msg := range expected {
   149  			t.Errorf("%s: %s\n", fset.Position(pos), msg)
   150  		}
   151  	}
   152  }
   153  
   154  func checkErrors(t *testing.T, filename string, input interface{}, mode Mode, expectErrors bool) {
   155  	t.Helper()
   156  	src, err := readSource(filename, input)
   157  	if err != nil {
   158  		t.Error(err)
   159  		return
   160  	}
   161  
   162  	fset := token.NewFileSet()
   163  	_, err = ParseFile(fset, filename, src, mode)
   164  	found, ok := err.(scanner.ErrorList)
   165  	if err != nil && !ok {
   166  		t.Error(err)
   167  		return
   168  	}
   169  	found.RemoveMultiples()
   170  
   171  	expected := map[token.Pos]string{}
   172  	if expectErrors {
   173  		// we are expecting the following errors
   174  		// (collect these after parsing a file so that it is found in the file set)
   175  		expected = expectedErrors(fset, filename, src)
   176  	}
   177  
   178  	// verify errors returned by the parser
   179  	compareErrors(t, fset, expected, found)
   180  }
   181  
   182  func TestErrors(t *testing.T) {
   183  	list, err := os.ReadDir(testdata)
   184  	if err != nil {
   185  		t.Fatal(err)
   186  	}
   187  	for _, d := range list {
   188  		name := d.Name()
   189  		if !d.IsDir() && !strings.HasPrefix(name, ".") && (strings.HasSuffix(name, ".src") || strings.HasSuffix(name, ".go2")) {
   190  			mode := DeclarationErrors | AllErrors
   191  			if strings.HasSuffix(name, ".go2") {
   192  				if !typeparams.Enabled {
   193  					continue
   194  				}
   195  			} else {
   196  				mode |= typeparams.DisallowParsing
   197  			}
   198  			checkErrors(t, filepath.Join(testdata, name), nil, mode, true)
   199  		}
   200  	}
   201  }
   202
View as plain text