Fixes #21: pre-releases not API compatible

CHANGELOG.md

@@ -1,3 +1,12 @@
+# Release 1.1.2 (unreleased)
+
+## Fixed
+- Issue #21: Per the SemVer spec (section 9) a pre-release is unstable and
+  might not satisfy the intended compatibility. The change here ignores pre-releases
+  on constraint checks (e.g., ~ or ^) when a pre-release is not part of the
+  constraint. For example, `^1.2.3` will ignore pre-releases while
+  `^1.2.3-alpha` will include them.
+
 # Release 1.1.1 (2016-06-30)
 
 ## Changed

README.md

@@ -78,6 +78,15 @@ The basic comparisons are:
 * `>=`: greater than or equal to
 * `<=`: less than or equal to
 
+_Note, according to the Semantic Version specification pre-releases may not be
+API compliant with their release counterpart. It says,_
+
+> _A pre-release version indicates that the version is unstable and might not satisfy the intended compatibility requirements as denoted by its associated normal version._
+
+_SemVer comparisons without a pre-release value will skip pre-release versions.
+For example, `>1.2.3` will skip pre-releases when looking at a list of values
+while `>1.2.3-alpha.1` will evaluate pre-releases._
+
 ## Hyphen Range Comparisons
 
 There are multiple methods to handle ranges and the first is hyphens ranges.

constraints.go

@@ -155,6 +155,14 @@ type constraint struct {
 
 // Check if a version meets the constraint
 func (c *constraint) check(v *Version) bool {
+
+	// If there is a pre-release on the version but the constraint isn't looking
+	// for them assume that pre-releases are not compatible. See issue 21 for
+	// more details.
+	if v.Prerelease() != "" && c.con.Prerelease() == "" {
+		return false
+	}
+
 	return c.function(v, c)
 }
 

constraints_test.go

@@ -152,6 +152,8 @@ func TestConstraintsCheck(t *testing.T) {
 		{"4.1.x", "4.1.3", true},
 		{"1.x", "1.4", true},
 		{"!=4.1", "4.1.0", false},
+		{"!=4.1-alpha", "4.1.0-alpha", false},
+		{"!=4.1-alpha", "4.1.0", true},
 		{"!=4.1", "5.1.0", true},
 		{"!=4.x", "5.1.0", true},
 		{"!=4.x", "4.1.0", false},
@@ -168,9 +170,12 @@ func TestConstraintsCheck(t *testing.T) {
 		{"<1.1.x", "1.1.500", true},
 		{"<1.2.x", "1.1.1", true},
 		{">=1.1", "4.1.0", true},
+		{">=1.1", "4.1.0-beta", false},
 		{">=1.1", "1.1.0", true},
 		{">=1.1", "0.0.9", false},
 		{"<=1.1", "0.1.0", true},
+		{"<=1.1", "0.1.0-alpha", false},
+		{"<=1.1-a", "0.1.0-alpha", true},
 		{"<=1.1", "1.1.0", true},
 		{"<=1.x", "1.1.0", true},
 		{"<=2.x", "3.1.0", false},
@@ -190,11 +195,18 @@ func TestConstraintsCheck(t *testing.T) {
 		{"^1.x", "1.1.1", true},
 		{"^2.x", "1.1.1", false},
 		{"^1.x", "2.1.1", false},
+		{"^1.x", "1.1.1-beta1", false},
+		{"^1.1.2-alpha", "1.2.1-beta1", true},
+		{"^1.2.x-alpha", "1.1.1-beta1", false},
 		{"~*", "2.1.1", true},
 		{"~1.x", "2.1.1", false},
 		{"~1.x", "1.3.5", true},
 		{"~1.x", "1.4", true},
 		{"~1.1", "1.1.1", true},
+		{"~1.1", "1.1.1-alpha", false},
+		{"~1.1-alpha", "1.1.1-beta", true},
+		{"~1.1.1-beta", "1.1.1-alpha", false},
+		{"~1.1.1-beta", "1.1.1", true},
 		{"~1.2.3", "1.2.5", true},
 		{"~1.2.3", "1.2.2", false},
 		{"~1.2.3", "1.3.2", false},
@@ -309,13 +321,20 @@ func TestConstraintsValidate(t *testing.T) {
 		{"1.1 - 2", "1.1.1", true},
 		{"1.1-3", "4.3.2", false},
 		{"^1.1", "1.1.1", true},
+		{"^1.1", "1.1.1-alpha", false},
+		{"^1.1.1-alpha", "1.1.1-beta", true},
+		{"^1.1.1-beta", "1.1.1-alpha", false},
 		{"^1.1", "4.3.2", false},
 		{"^1.x", "1.1.1", true},
 		{"^2.x", "1.1.1", false},
 		{"^1.x", "2.1.1", false},
 		{"~*", "2.1.1", true},
 		{"~1.x", "2.1.1", false},
 		{"~1.x", "1.3.5", true},
+		{"~1.x", "1.3.5-beta", false},
+		{"~1.3.6-alpha", "1.3.5-beta", false},
+		{"~1.3.5-alpha", "1.3.5-beta", true},
+		{"~1.3.5-beta", "1.3.5-alpha", false},
 		{"~1.x", "1.4", true},
 		{"~1.1", "1.1.1", true},
 		{"~1.2.3", "1.2.5", true},