Go: Add SemVer type to track valid semantic versions

Author: mbg

go/extractor/util/BUILD.bazel

@@ -0,0 +1,109 @@
+package util
+
+import (
+	"log"
+	"strings"
+
+	"golang.org/x/mod/semver"
+)
+
+// A type used to represent values known to be valid semantic versions.
+type SemVer interface {
+	String() string
+	// Compares this semantic version against the `other`. Returns the following values:
+	//
+	// 0 if both versions are equal.
+	//
+	// -1 if this version is older than the `other`.
+	//
+	// 1 if this version is newer than the `other`.
+	Compare(other SemVer) int
+	// Returns true if this version is newer than the `other`, or false otherwise.
+	IsNewerThan(other SemVer) bool
+	// Returns true if this version is equal to `other` or newer, or false otherwise.
+	IsAtLeast(other SemVer) bool
+	// Returns true if this version is older than the `other`, or false otherwise.
+	IsOlderThan(other SemVer) bool
+	// Returns true if this version is equal to `other` or older, or false otherwise.
+	IsAtMost(other SemVer) bool
+	// Returns the `major.minor` version prefix of the semantic version. For example, "v1.2.3" becomes "v1.2".
+	MajorMinor() SemVer
+}
+
+// The internal representation used for values known to be valid semantic versions.
+//
+// NOTE: Not exported to prevent invalid values from being constructed.
+type semVer string
+
+// Converts the semantic version to a string representation.
+func (ver semVer) String() string {
+	return string(ver)
+}
+
+// Represents `v0.0.0`.
+func Zero() SemVer {
+	return semVer("v0.0.0")
+}
+
+// Constructs a [SemVer] from the given `version` string. The input can be any valid version string
+// that we commonly deal with. This includes ordinary version strings such as "1.2.3", ones with
+// the "go" prefix, and ones with the "v" prefix. Go's non-semver-compliant release candidate
+// versions are also automatically corrected from e.g. "go1.20rc1" to "v1.20-rc1". If given
+// the empty string, this function return `nil`. Otherwise, for invalid version strings, the function
+// prints a message to the log and exits the process.
+func NewSemVer(version string) SemVer {
+	// If the input is the empty string, return nil f
+	if version == "" {
+		return nil
+	}
+
+	// Drop a "go" prefix, if there is one.
+	version = strings.TrimPrefix(version, "go")
+
+	// Go versions don't follow the SemVer format, but the only exception we normally care about
+	// is release candidates; so this is a horrible hack to convert e.g. `1.22rc1` into `1.22-rc1`
+	// which is compatible with the SemVer specification.
+	rcIndex := strings.Index(version, "rc")
+	if rcIndex != -1 {
+		version = semver.Canonical("v"+version[:rcIndex]) + "-" + version[rcIndex:]
+	}
+
+	// Add the "v" prefix that is required by the `semver` package.
+	if !strings.HasPrefix(version, "v") {
+		version = "v" + version
+	}
+
+	// Convert the remaining version string to a canonical semantic version,
+	// and check that this was successful.
+	canonical := semver.Canonical(version)
+
+	if canonical == "" {
+		log.Fatalf("%s is not a valid version string\n", version)
+	}
+
+	return semVer(canonical)
+}
+
+func (ver semVer) Compare(other SemVer) int {
+	return semver.Compare(string(ver), string(other.String()))
+}
+
+func (ver semVer) IsNewerThan(other SemVer) bool {
+	return ver.Compare(other) > 0
+}
+
+func (ver semVer) IsAtLeast(other SemVer) bool {
+	return ver.Compare(other) >= 0
+}
+
+func (ver semVer) IsOlderThan(other SemVer) bool {
+	return ver.Compare(other) < 0
+}
+
+func (ver semVer) IsAtMost(other SemVer) bool {
+	return ver.Compare(other) <= 0
+}
+
+func (ver semVer) MajorMinor() SemVer {
+	return semVer(semver.MajorMinor(string(ver)))
+}

go/extractor/util/semver.go

@@ -0,0 +1,60 @@
+package util
+
+import "testing"
+
+func TestNewSemVer(t *testing.T) {
+	type TestPair struct {
+		Input    string
+		Expected string
+	}
+
+	// Check the special case for the empty string.
+	result := NewSemVer("")
+	if result != nil {
+		t.Errorf("Expected NewSemVer(\"\") to return nil, but got \"%s\".", result)
+	}
+
+	testData := []TestPair{
+		{"0", "v0.0.0"},
+		{"1.0", "v1.0.0"},
+		{"1.0.2", "v1.0.2"},
+		{"1.20", "v1.20.0"},
+		{"1.22.3", "v1.22.3"},
+	}
+
+	// Check that we get what we expect for each of the test cases.
+	for _, pair := range testData {
+		result := NewSemVer(pair.Input)
+
+		if result.String() != pair.Expected {
+			t.Errorf("Expected NewSemVer(\"%s\") to return \"%s\", but got \"%s\".", pair.Input, pair.Expected, result)
+		}
+	}
+
+	// And again, but this time prefixed with "v"
+	for _, pair := range testData {
+		result := NewSemVer("v" + pair.Input)
+
+		if result.String() != pair.Expected {
+			t.Errorf("Expected NewSemVer(\"v%s\") to return \"%s\", but got \"%s\".", pair.Input, pair.Expected, result)
+		}
+	}
+
+	// And again, but this time prefixed with "go"
+	for _, pair := range testData {
+		result := NewSemVer("go" + pair.Input)
+
+		if result.String() != pair.Expected {
+			t.Errorf("Expected NewSemVer(\"go%s\") to return \"%s\", but got \"%s\".", pair.Input, pair.Expected, result)
+		}
+	}
+
+	// And again, but this time with an "rc1" suffix.
+	for _, pair := range testData {
+		result := NewSemVer(pair.Input + "rc1")
+
+		if result.String() != pair.Expected+"-rc1" {
+			t.Errorf("Expected NewSemVer(\"%src1\") to return \"%s\", but got \"%s\".", pair.Input, pair.Expected+"-rc1", result)
+		}
+	}
+}