func GoVersion(x Expr) string
GoVersion returns the minimum Go version implied by a given build expression. If the expression can be satisfied without any Go version tags, GoVersion returns an empty string.
For example:
GoVersion(linux && go1.22) = "go1.22" GoVersion((linux && go1.22) || (windows && go1.20)) = "go1.20" => go1.20 GoVersion(linux) = "" GoVersion(linux || (windows && go1.22)) = "" GoVersion(!go1.22) = ""
GoVersion assumes that any tag or negated tag may independently be true, so that its analysis can be purely structural, without SAT solving. “Impossible” subexpressions may therefore affect the result.
For example:
GoVersion((linux && !linux && go1.20) || go1.21) = "go1.20"
func IsGoBuild(line string) bool
IsGoBuild reports whether the line of text is a “//go:build” constraint. It only checks the prefix of the text, not that the expression itself parses.
func IsPlusBuild(line string) bool
IsPlusBuild reports whether the line of text is a “// +build” constraint. It only checks the prefix of the text, not that the expression itself parses.
func PlusBuildLines(x Expr) ([]string, error)
PlusBuildLines returns a sequence of “// +build” lines that evaluate to the build expression x. If the expression is too complex to convert directly to “// +build” lines, PlusBuildLines returns an error.
An AndExpr represents the expression X && Y.
type AndExpr struct {
X, Y Expr
}
func (x *AndExpr) Eval(ok func(tag string) bool) bool
func (x *AndExpr) String() string
An Expr is a build tag constraint expression. The underlying concrete type is *AndExpr, *OrExpr, *NotExpr, or *TagExpr.
type Expr interface {
// String returns the string form of the expression,
// using the boolean syntax used in //go:build lines.
String() string
// Eval reports whether the expression evaluates to true.
// It calls ok(tag) as needed to find out whether a given build tag
// is satisfied by the current build configuration.
Eval(ok func(tag string) bool) bool
// contains filtered or unexported methods
}
func Parse(line string) (Expr, error)
Parse parses a single build constraint line of the form “//go:build ...” or “// +build ...” and returns the corresponding boolean expression.
A NotExpr represents the expression !X (the negation of X).
type NotExpr struct {
X Expr
}
func (x *NotExpr) Eval(ok func(tag string) bool) bool
func (x *NotExpr) String() string
An OrExpr represents the expression X || Y.
type OrExpr struct {
X, Y Expr
}
func (x *OrExpr) Eval(ok func(tag string) bool) bool
func (x *OrExpr) String() string
A SyntaxError reports a syntax error in a parsed build expression.
type SyntaxError struct {
Offset int // byte offset in input where error was detected
Err string // description of error
}
func (e *SyntaxError) Error() string
A TagExpr is an Expr for the single tag Tag.
type TagExpr struct {
Tag string // for example, “linux” or “cgo”
}
func (x *TagExpr) Eval(ok func(tag string) bool) bool
func (x *TagExpr) String() string