fix issue with getReplacement when version is empty string

It is possible that JakartaPackageAlignmentPlugin will call
getReplacement with an empty string for the version. Previously, this
code would erroneously return a replacement version because the
comparator for ComparableVersion returns -1 when an empty string is
compared with the maximum Jakarta version.

To address that, only look for a replacement when the version is
non-null and non-empty.

Fixes #25

jakarta-package-alignment-mappings/src/main/java/com/palantir/gradle/jakartapackagealignment/VersionMappings.java

@@ -28,6 +28,14 @@ public final class VersionMappings {
     private VersionMappings() {}
 
     public static Optional<MavenCoordinate> getReplacement(String group, String name, String version) {
+        // https://github.com/palantir/jakarta-package-alignment/issues/25
+        // we must have non-null, non-empty version, otherwise the version comparison below
+        // can return the incorrect result
+        // this can happen if getReplacement is called from a ModuleComponentSelector that only has the group/name set
+        if (version == null || version.isEmpty()) {
+            return Optional.empty();
+        }
+
         String key = group + ":" + name;
         VersionMapping mapping = mappings.get(key);
 

jakarta-package-alignment/src/test/groovy/com/palantir/gradle/jakartapackagealignment/JakartaPackageAlignmentPluginIntegrationSpec.groovy

@@ -20,6 +20,7 @@ import groovy.transform.CompileStatic
 import nebula.test.IntegrationSpec
 import nebula.test.dependencies.DependencyGraph
 import nebula.test.dependencies.GradleDependencyGenerator
+import nebula.test.functional.ExecutionResult
 
 /**
  * Integration tests for {@link JakartaPackageAlignmentPlugin}.
@@ -110,4 +111,41 @@ class JakartaPackageAlignmentPluginIntegrationSpec extends IntegrationSpec {
         versionsLockFile.text.contains("jakarta.servlet:jakarta.servlet-api:5.0.0")
         !versionsLockFile.text.contains("javax.servlet:javax.servlet-api")
     }
+
+    def "leaves usage of acceptable versions untouched, but still replaces bad versions"() {
+        setup:
+        mavenRepo = generateMavenRepo(
+                "org:direct-dep:1.0.0 -> org:transitive-dep:1.2.3",
+                "org:transitive-dep:1.2.3 -> jakarta.ws.rs:jakarta.ws.rs-api:2.1.6",
+                "org:direct-dep:2.0.0 -> org:transitive-dep:2.0.0",
+                "org:transitive-dep:2.0.0 -> jakarta.servlet:jakarta.servlet-api:5.0.0",
+                "jakarta.ws.rs:jakarta.ws.rs-api:3.1.0",
+                "jakarta.ws.rs:jakarta.ws.rs-api:2.1.6",
+                "javax.ws.rs:javax.ws.rs-api:2.1.1"
+        )
+
+        buildFile << """
+            dependencies {
+                implementation "org:direct-dep"
+                implementation "jakarta.ws.rs:jakarta.ws.rs-api"
+            }
+        """.stripIndent()
+
+        // no idea why stripIndent isnt working here, maybe the encoding on this file is weird?
+        versionsProps << """org:direct-dep = 1.0.0\njakarta.ws.rs:jakarta.ws.rs-api = 3.1.0""".stripIndent()
+
+        when:
+        runTasksSuccessfully("--write-locks")
+        ExecutionResult result = runTasksSuccessfully("dependencies", "--configuration", "runtimeClasspath")
+
+        then:
+        def versionsLockFile = new File(projectDir, "versions.lock")
+        fileExists("versions.lock")
+        versionsLockFile.text.contains("jakarta.ws.rs:jakarta.ws.rs-api:3.1.0")
+        versionsLockFile.text.contains("javax.ws.rs:javax.ws.rs-api:2.1.1")
+        !versionsLockFile.text.contains("jakarta.ws.rs:jakarta.ws.rs-api:2.1.6")
+
+        result.standardOutput.contains("jakarta.ws.rs:jakarta.ws.rs-api -> 3.1.0")
+        result.standardOutput.contains("jakarta.ws.rs:jakarta.ws.rs-api:2.1.6 -> javax.ws.rs:javax.ws.rs-api:2.1.1")
+    }
 }