Look for the embedded binary only when it would run

FormatterProvider asks for the formatter on every file formatted, and
finding the embedded binary lists a directory. Most projects run the
Java-based formatter, or a binary of the user's own, and need no such
lookup, so FormatterSelection now takes the embedded binary as a
Supplier and asks only when nothing else decides.

Removing an earlier session's leftovers now happens once per IDE
session too: projects that open together would otherwise race to
delete the same directories and log each other's misses.

Author: abashev

open-java-format-idea-plugin/src/main/java/com/palantir/javaformat/intellij/EmbeddedNativeImage.java

@@ -69,6 +69,7 @@ final class EmbeddedNativeImage {
     private final AtomicReference<Activity> activity = new AtomicReference<>(new Activity.Idle());
     private final List<Runnable> listeners = new CopyOnWriteArrayList<>();
     private final AtomicBoolean noticeShown = new AtomicBoolean();
+    private final AtomicBoolean staleRemoved = new AtomicBoolean();
 
     EmbeddedNativeImage() {
         this(
@@ -243,10 +244,11 @@ Installed install(String version, ProgressIndicator indicator) throws IOExceptio
 
     /**
      * Removes what an earlier session could not: the binaries of other versions, one of which Windows may have held
-     * open while it formatted, and unfinished downloads. Never while a download is under way, whose file would go too.
+     * open while it formatted, and unfinished downloads. Once per IDE session, by the first project that opens, and
+     * never while a download is under way, whose file would go too.
      */
     void removeStale() {
-        if (!(activity.get() instanceof Activity.Downloading)) {
+        if (!(activity.get() instanceof Activity.Downloading) && staleRemoved.compareAndSet(false, true)) {
             removeAllBut(installed().map(Installed::version).orElse(""));
         }
     }

open-java-format-idea-plugin/src/main/java/com/palantir/javaformat/intellij/FormatterProvider.java

@@ -61,7 +61,7 @@ Optional<FormatterService> get(Project project, PalantirJavaFormatSettings setti
                 project,
                 settings.getImplementationClassPath(),
                 settings.injectedVersionIsOutdated(),
-                FormatterSelection.of(settings, embeddedNativeImage.get())));
+                FormatterSelection.of(settings, embeddedNativeImage)));
     }
 
     private static Optional<FormatterService> createFormatter(FormatterCacheKey cacheKey) {

open-java-format-idea-plugin/src/main/java/com/palantir/javaformat/intellij/FormatterSelection.java

@@ -16,6 +16,7 @@
 
 import java.nio.file.Path;
 import java.util.Optional;
+import java.util.function.Supplier;
 
 /**
  * Which formatter a project's settings run. FormatterProvider starts it, and the settings page shows it as the
@@ -25,15 +26,16 @@ sealed interface FormatterSelection {
 
     /**
      * A path of the user's own wins over the embedded binary. Without either, the Java-based formatter runs even with
-     * the native one switched on: the embedded binary may not be downloaded yet.
+     * the native one switched on: the embedded binary may not be downloaded yet. The embedded binary is looked for
+     * only when it would run, since that lists a directory and this runs for every file formatted.
      */
-    static FormatterSelection of(PalantirJavaFormatSettings settings, Optional<Path> embeddedNativeImage) {
+    static FormatterSelection of(PalantirJavaFormatSettings settings, Supplier<Optional<Path>> embeddedNativeImage) {
         if (!settings.useNativeImage()) {
             return new JavaBased(false);
         }
         return settings.getNativeImagePath()
                 .<FormatterSelection>map(path -> new NativeImage(path, false))
-                .or(() -> embeddedNativeImage.map(path -> new NativeImage(path, true)))
+                .or(() -> embeddedNativeImage.get().map(path -> new NativeImage(path, true)))
                 .orElseGet(() -> new JavaBased(true));
     }
 

open-java-format-idea-plugin/src/main/java/com/palantir/javaformat/intellij/PalantirJavaFormatConfigurable.java

@@ -235,7 +235,7 @@ private void showEmbeddedNativeImage() {
         embeddedAction.setVisible(line.action().isPresent());
         // What runs with the settings as applied: the embedded binary can arrive while the page is open.
         formatterType.setText(FormatterSelection.of(
-                        PalantirJavaFormatSettings.getInstance(project), embeddedNativeImage.installedPath())
+                        PalantirJavaFormatSettings.getInstance(project), embeddedNativeImage::installedPath)
                 .describe());
     }
 

open-java-format-idea-plugin/src/test/java/com/palantir/javaformat/intellij/FormatterSelectionTest.java

@@ -20,6 +20,7 @@
 import com.palantir.javaformat.intellij.FormatterSelection.NativeImage;
 import java.nio.file.Path;
 import java.util.Optional;
+import java.util.function.Supplier;
 import org.junit.jupiter.api.Test;
 
 final class FormatterSelectionTest {
@@ -34,28 +35,43 @@ void runsTheBinaryTheUserChose() {
         settings.setUseNativeImage(true);
         settings.setNativeImagePath(Optional.of(CUSTOM));
 
-        assertThat(FormatterSelection.of(settings, Optional.of(EMBEDDED))).isEqualTo(new NativeImage(CUSTOM, false));
+        assertThat(FormatterSelection.of(settings, () -> Optional.of(EMBEDDED)))
+                .isEqualTo(new NativeImage(CUSTOM, false));
     }
 
     @Test
     void runsTheEmbeddedBinaryWithoutAPathOfTheUsersOwn() {
         settings.setUseNativeImage(true);
 
-        assertThat(FormatterSelection.of(settings, Optional.of(EMBEDDED))).isEqualTo(new NativeImage(EMBEDDED, true));
+        assertThat(FormatterSelection.of(settings, () -> Optional.of(EMBEDDED)))
+                .isEqualTo(new NativeImage(EMBEDDED, true));
     }
 
     @Test
     void fallsBackToTheJavaBasedFormatterWithoutABinary() {
         settings.setUseNativeImage(true);
 
-        assertThat(FormatterSelection.of(settings, Optional.empty())).isEqualTo(new JavaBased(true));
+        assertThat(FormatterSelection.of(settings, Optional::empty)).isEqualTo(new JavaBased(true));
     }
 
     @Test
     void runsTheJavaBasedFormatterUnlessTheNativeOneIsOn() {
         settings.setNativeImagePath(Optional.of(CUSTOM));
 
-        assertThat(FormatterSelection.of(settings, Optional.of(EMBEDDED))).isEqualTo(new JavaBased(false));
+        assertThat(FormatterSelection.of(settings, () -> Optional.of(EMBEDDED))).isEqualTo(new JavaBased(false));
+    }
+
+    @Test
+    void looksForTheEmbeddedBinaryOnlyWhenItWouldRun() {
+        // It is asked for every file formatted, and most projects run the Java-based formatter.
+        Supplier<Optional<Path>> unasked = () -> {
+            throw new AssertionError("the embedded binary was looked for");
+        };
+        settings.setNativeImagePath(Optional.of(CUSTOM));
+
+        assertThat(FormatterSelection.of(settings, unasked)).isEqualTo(new JavaBased(false));
+        settings.setUseNativeImage(true);
+        assertThat(FormatterSelection.of(settings, unasked)).isEqualTo(new NativeImage(CUSTOM, false));
     }
 
     @Test