version.go

     1  // Copyright 2023 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 version provides operations on [Go versions]
     6  // in [Go toolchain name syntax]: strings like
     7  // "go1.20", "go1.21.0", "go1.22rc2", and "go1.23.4-bigcorp".
     8  //
     9  // [Go versions]: https://go.dev/doc/toolchain#version
    10  // [Go toolchain name syntax]: https://go.dev/doc/toolchain#name
    11  package version // import "go/version"
    12  
    13  import (
    14  	"internal/gover"
    15  	"strings"
    16  )
    17  
    18  // stripGo converts from a "go1.21-bigcorp" version to a "1.21" version.
    19  // If v does not start with "go", stripGo returns the empty string (a known invalid version).
    20  func stripGo(v string) string {
    21  	v, _, _ = strings.Cut(v, "-") // strip -bigcorp suffix.
    22  	if len(v) < 2 || v[:2] != "go" {
    23  		return ""
    24  	}
    25  	return v[2:]
    26  }
    27  
    28  // Lang returns the Go language version for version x.
    29  // If x is not a valid version, Lang returns the empty string.
    30  // For example:
    31  //
    32  //	Lang("go1.21rc2") = "go1.21"
    33  //	Lang("go1.21.2") = "go1.21"
    34  //	Lang("go1.21") = "go1.21"
    35  //	Lang("go1") = "go1"
    36  //	Lang("bad") = ""
    37  //	Lang("1.21") = ""
    38  func Lang(x string) string {
    39  	v := gover.Lang(stripGo(x))
    40  	if v == "" {
    41  		return ""
    42  	}
    43  	if strings.HasPrefix(x[2:], v) {
    44  		return x[:2+len(v)] // "go"+v without allocation
    45  	} else {
    46  		return "go" + v
    47  	}
    48  }
    49  
    50  // Compare returns -1, 0, or +1 depending on whether
    51  // x < y, x == y, or x > y, interpreted as Go versions.
    52  // The versions x and y must begin with a "go" prefix: "go1.21" not "1.21".
    53  // Invalid versions, including the empty string, compare less than
    54  // valid versions and equal to each other.
    55  // The language version "go1.21" compares less than the
    56  // release candidate and eventual releases "go1.21rc1" and "go1.21.0".
    57  func Compare(x, y string) int {
    58  	return gover.Compare(stripGo(x), stripGo(y))
    59  }
    60  
    61  // IsValid reports whether the version x is valid.
    62  func IsValid(x string) bool {
    63  	return gover.IsValid(stripGo(x))
    64  }
    65
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