add overloads to load a custom scalafix version

Author: bjaglin

scalafix-interfaces/src/main/java/scalafix/interfaces/Scalafix.java

@@ -136,7 +136,98 @@ static Scalafix fetchAndClassloadInstance(String requestedScalaVersion) throws S
      */
     static Scalafix fetchAndClassloadInstance(String requestedScalaVersion, List<Repository> repositories)
             throws ScalafixException {
+        Properties properties = new Properties();
+        String propertiesPath = "scalafix-interfaces.properties";
+        try {
+            InputStream stream = Scalafix.class.getClassLoader().getResourceAsStream(propertiesPath);
+            properties.load(stream);
+            return fetchAndClassloadInstance(properties, requestedScalaVersion, repositories);
+        } catch (Exception e) {
+            System.err.println(
+                "Failed to load '" + propertiesPath +  "' from local artifact, " +
+                "falling back to fetching the latest scalafix version...");
+
+            String latestVersion;
+            try {
+                latestVersion = ScalafixCoursier.latestScalafixProperties(repositories);
+            } catch (Exception ee) {
+                throw new ScalafixException(
+                    "Failed to lookup latest scalafix version", ee);
+            }   
+            return fetchAndClassloadInstance(latestVersion, requestedScalaVersion, repositories);
+        }
+    }
+
+    /**
+     * Fetch JARs containing an implementation of {@link Scalafix} using Coursier and classload an instance of it via
+     * runtime reflection.
+     * <p>
+     * The custom classloader optionally provided with {@link ScalafixArguments#withToolClasspath} to compile and
+     * classload external rules must have the classloader of the returned instance as ancestor to share a common
+     * loaded instance of `scalafix-core`, and therefore have been compiled against the requested Scala version.
+     *
+     * @param scalafixVersion    Fetch a specific, implementation of {@link Scalafix}. Must be binary-compatible.
+     * @param requestedScalaVersion A full Scala version (i.e. "3.3.4") or a major.minor one (i.e. "3.3") to infer
+     *                              the major.minor Scala version that should be available in the classloader of the
+     *                              returned instance. To be able to run advanced semantic rules using the Scala
+     *                              Presentation Compiler such as ExplicitResultTypes, this must be source-compatible
+     *                              with the version that the target classpath is built with, as provided with
+     *                              {@link ScalafixArguments#withScalaVersion}.
+     * @return An implementation of the {@link Scalafix} interface.
+     * @throws ScalafixException in case of errors during artifact resolution/fetching.
+     */
+    static Scalafix fetchAndClassloadInstance(String scalafixVersion,  String requestedScalaVersion )
+            throws ScalafixException {
+        return fetchAndClassloadInstance(scalafixVersion, requestedScalaVersion, Repository.defaults());
+    }
+
+    /**
+     * Fetch JARs containing an implementation of {@link Scalafix} from the provided repositories using Coursier and
+     * classload an instance of it via runtime reflection.
+     * <p>
+     * The custom classloader optionally provided with {@link ScalafixArguments#withToolClasspath} to compile and
+     * classload external rules must have the classloader of the returned instance as ancestor to share a common
+     * loaded instance of `scalafix-core`, and therefore have been compiled against the requested Scala version.
+     *
+     * @param scalafixVersion    Fetch a specific, implementation of {@link Scalafix}. Must be binary-compatible.
+     * @param requestedScalaVersion A full Scala version (i.e. "3.3.4") or a major.minor one (i.e. "3.3") to infer
+     *                              the major.minor Scala version that should be available in the classloader of the
+     *                              returned instance. To be able to run advanced semantic rules using the Scala
+     *                              Presentation Compiler such as ExplicitResultTypes, this must be source-compatible
+     *                              with the version that the target classpath is built with, as provided with
+     *                              {@link ScalafixArguments#withScalaVersion}.
+     * @param repositories       Maven/Ivy repositories to fetch the JARs from.
+     * @return An implementation of the {@link Scalafix} interface.
+     * @throws ScalafixException in case of errors during artifact resolution/fetching.
+     */
+    static Scalafix fetchAndClassloadInstance(
+        String scalafixVersion,
+        String requestedScalaVersion,
+        List<Repository> repositories
+    ) throws ScalafixException {
+        Properties properties = new Properties();
+        String propertiesPath = "scalafix-interfaces.properties";
+        try {
+            List<URL> jars = ScalafixCoursier.scalafixPropertiesJars(repositories, scalafixVersion);
+            URLClassLoader classLoader =
+                new URLClassLoader(jars.stream().toArray(URL[]::new), null);
+            
+            InputStream stream = classLoader.getResourceAsStream(propertiesPath);
+            properties.load(stream);
+        } catch (Exception e) {
+            throw new ScalafixException(
+                "Failed to fetch '" + propertiesPath + "' for scalafix version " + scalafixVersion,
+                e);
+        }
 
+        return fetchAndClassloadInstance(properties, requestedScalaVersion, repositories);
+    }
+
+    private static Scalafix fetchAndClassloadInstance(
+        Properties properties,
+        String requestedScalaVersion,
+        List<Repository> repositories
+    ) throws ScalafixException {
         String requestedScalaMajorMinorOrMajorVersion =
             requestedScalaVersion.replaceAll("^(\\d+\\.\\d+).*", "$1");
 
@@ -161,34 +252,10 @@ static Scalafix fetchAndClassloadInstance(String requestedScalaVersion, List<Rep
             throw new IllegalArgumentException("Unsupported scala version " + requestedScalaVersion);
         }
 
-        Properties properties = new Properties();
-        String propertiesPath = "scalafix-interfaces.properties";
-        try {
-            InputStream stream = Scalafix.class.getClassLoader().getResourceAsStream(propertiesPath);
-            properties.load(stream);
-        } catch (Exception e) {
-            System.err.println(
-                "Failed to load '" + propertiesPath +  "' from local artifact, " +
-                "falling back to fetching the latest scalafix version...");
-
-            try {
-                List<URL> jars = ScalafixCoursier.latestScalafixPropertiesJars(repositories);
-                URLClassLoader classLoader =
-                    new URLClassLoader(jars.stream().toArray(URL[]::new), null);
-                
-                InputStream stream = classLoader.getResourceAsStream(propertiesPath);
-                properties.load(stream);
-            } catch (Exception ee) {
-                throw new ScalafixException(
-                    "Failed to load '" + propertiesPath + "' from local & remote artifacts",
-                    ee);
-            }
-        }
-
         String scalafixVersion = properties.getProperty("scalafixVersion");
         String scalaVersion = properties.getProperty(scalaVersionKey);
         if (scalafixVersion == null || scalaVersion == null)
-            throw new ScalafixException("Failed to lookup versions from '" + propertiesPath + "'");
+            throw new ScalafixException("Failed to lookup versions from properties file");
 
         List<URL> jars = ScalafixCoursier.scalafixCliJars(repositories, scalafixVersion, scalaVersion);
         ClassLoader parent = new ScalafixInterfacesClassloader(Scalafix.class.getClassLoader());

scalafix-interfaces/src/main/java/scalafix/internal/interfaces/ScalafixCoursier.java

@@ -59,20 +59,26 @@ private static List<URL> toURLs(FetchResult result) throws ScalafixException {
         return urls;
     }
 
-    public static List<URL> latestScalafixPropertiesJars(
+    public static String latestScalafixProperties(
             List<Repository> repositories
     ) throws ScalafixException {
         Module module = Module.of("ch.epfl.scala", "scalafix-properties");
         String allowedVersion = System.getProperty("scalafix-properties.version");
-        String version = versions(repositories, module)
+        return versions(repositories, module)
                 .getAvailable()
                 .stream()
                 // Ignore RC & SNAPSHOT versions, except if explicitly requested
                 .filter(v -> !v.contains("-") || v.equals(allowedVersion))
                 .reduce((older, newer) -> newer)
                 .orElseThrow(() -> new ScalafixException("Could not find any stable version for " + module)); 
+    }
 
-        Dependency scalafixProperties = Dependency.of(module, version);
+    public static List<URL> scalafixPropertiesJars(
+            List<Repository> repositories,
+            String scalafixVersion
+    ) throws ScalafixException {
+        Module module = Module.of("ch.epfl.scala", "scalafix-properties");
+        Dependency scalafixProperties = Dependency.of(module, scalafixVersion);
         return toURLs(fetch(repositories, Collections.singletonList(scalafixProperties), ResolutionParams.create()));
     }