Documentation
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Overview ¶
Package constraint implements parsing and evaluation of build constraint lines. See https://golang.org/cmd/go/#hdr-Build_constraints for documentation about build constraints themselves.
This package parses both the original “// +build” syntax and the “//go:build” syntax that was added in Go 1.17. See https://golang.org/design/draft-gobuild for details about the “//go:build” syntax.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func GoVersion ¶ added in go1.21.0
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 ¶
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 ¶
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 ¶
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.
Types ¶
type Expr ¶
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
}
An Expr is a build tag constraint expression. The underlying concrete type is *AndExpr, *OrExpr, *NotExpr, or *TagExpr.
type NotExpr ¶
type NotExpr struct {
X Expr
}
A NotExpr represents the expression !X (the negation of X).
type SyntaxError ¶
type SyntaxError struct {
Offset int // byte offset in input where error was detected
Err string // description of error
}
A SyntaxError reports a syntax error in a parsed build expression.
func (*SyntaxError) Error ¶
func (e *SyntaxError) Error() string
Source Files