fix(gradle): run the unpacked wrapper distribution when gradle-wrapper.jar is missing

A *.jar rule in .gitignore often leaves gradle/wrapper/gradle-wrapper.jar out of
the repository, and gradlew then fails with only "could not find or load main
class org.gradle.wrapper.GradleWrapperMain". When the jar is missing, the
distribution named by gradle-wrapper.properties is run from the Gradle user
home's wrapper/dists if the wrapper already unpacked it; otherwise the wrapper
runs as before and its failure is summarised as the missing jar with what to do.

crates/ide-build/src/sync.rs

@@ -270,6 +270,13 @@ fn run(
 
 /// The first error lines of a failed build, for the tool window.
 pub(crate) fn error_summary(text: &str) -> String {
+    // The JVM's "could not find or load main class" (localized) when `gradlew` has no jar.
+    if text.contains("org.gradle.wrapper.GradleWrapperMain") {
+        return "gradle/wrapper/gradle-wrapper.jar is missing (often excluded by a `*.jar` rule in .gitignore). \
+                Restore it, run `gradle wrapper` with an installed Gradle, or choose Distribution: Local installation \
+                in Settings › Build, Execution, Deployment › Gradle."
+            .to_owned();
+    }
     let lines: Vec<&str> = text
         .lines()
         .filter(|l| {
@@ -909,6 +916,8 @@ mod tests {
         let text = "[INFO] x\n[ERROR] Failed to execute goal\n[ERROR] \n[ERROR] Re-run Maven using -X\n";
         assert_eq!(error_summary(text), "Failed to execute goal");
         assert_eq!(error_summary("one\nlast line\n\n"), "last line");
+        let missing_jar = "错误: 找不到或无法加载主类 org.gradle.wrapper.GradleWrapperMain\n";
+        assert!(error_summary(missing_jar).starts_with("gradle/wrapper/gradle-wrapper.jar is missing"));
     }
 
     #[test]

crates/ide-sdk/src/apply.rs

@@ -323,6 +323,18 @@ fn resolve_gradle_command(root: &Path, build_dir: &Path, s: &Settings, use_wrapp
     }
     let wrapper = build_dir.join(if cfg!(windows) { "gradlew.bat" } else { "gradlew" });
     if use_wrapper && wrapper.is_file() {
+        // `gradlew` can't start without its jar, which `.gitignore`s with `*.jar` often leave
+        // out: run the distribution the wrapper already unpacked instead.
+        if build_dir.join("gradle/wrapper/gradle-wrapper.jar").is_file() {
+            return wrapper;
+        }
+        let home = setting_path(root, &g.user_home)
+            .or_else(|| std::env::var_os("GRADLE_USER_HOME").map(PathBuf::from))
+            .or_else(|| Some(crate::home_dir()?.join(".gradle")));
+        if let Some(gradle) = home.and_then(|home| unpacked_wrapper_distribution(build_dir, &home)) {
+            return gradle;
+        }
+        // Nothing to run instead: the wrapper's failure explains what is missing.
         return wrapper;
     }
     pinned::pinned_install(build_dir, Tool::Gradle)
@@ -330,6 +342,21 @@ fn resolve_gradle_command(root: &Path, build_dir: &Path, s: &Settings, use_wrapp
         .unwrap_or_else(|| name.into())
 }
 
+/// `bin/gradle` of the distribution `gradle/wrapper/gradle-wrapper.properties` names, once the
+/// wrapper has unpacked it in `<gradle_user_home>/wrapper/dists` (and marked it complete).
+fn unpacked_wrapper_distribution(build_dir: &Path, gradle_user_home: &Path) -> Option<PathBuf> {
+    let properties = std::fs::read_to_string(build_dir.join("gradle/wrapper/gradle-wrapper.properties")).ok()?;
+    let url = properties.lines().find_map(|line| line.trim().strip_prefix("distributionUrl="))?;
+    let zip = url.trim().replace("\\:", ":").rsplit('/').next()?.to_owned();
+    let name = zip.strip_suffix(".zip")?;
+    let gradle = if cfg!(windows) { "gradle.bat" } else { "gradle" };
+    // One directory per distribution URL hash, each holding the unpacked `gradle-<version>`.
+    let hashes = std::fs::read_dir(gradle_user_home.join("wrapper/dists").join(name)).ok()?;
+    hashes.flatten().map(|e| e.path()).filter(|dir| dir.join(format!("{zip}.ok")).is_file()).find_map(|dir| {
+        std::fs::read_dir(&dir).ok()?.flatten().map(|e| e.path().join("bin").join(gradle)).find(|p| p.is_file())
+    })
+}
+
 fn gradle_run_jdk<'a>(
     release: Option<u32>,
     configured: Option<&'a crate::java::Jdk>,

crates/ide-sdk/src/tests.rs

@@ -1866,6 +1866,37 @@ fn max_java_picks_an_older_jdk() {
     assert_eq!(free.env["JAVA_HOME"], j25.home.to_string_lossy());
 }
 
+/// #3086: `gradle-wrapper.jar` excluded by a `*.jar` rule in `.gitignore`: `gradlew` can't
+/// start, so the distribution the wrapper already unpacked runs instead.
+#[test]
+fn gradle_wrapper_without_its_jar_runs_the_unpacked_distribution() {
+    use crate::apply::gradle_command;
+    let tmp = tempfile::tempdir().unwrap();
+    let root = tmp.path();
+    let plain = if cfg!(windows) { "gradle.bat" } else { "gradle" };
+    let wrapper = root.join(if cfg!(windows) { "gradlew.bat" } else { "gradlew" });
+    std::fs::write(&wrapper, "").unwrap();
+    std::fs::create_dir_all(root.join("gradle/wrapper")).unwrap();
+    std::fs::write(
+        root.join("gradle/wrapper/gradle-wrapper.properties"),
+        "distributionUrl=https\\://services.gradle.org/distributions/gradle-4.10-bin.zip\n",
+    )
+    .unwrap();
+    let mut settings = Settings::default();
+    settings.languages.java.gradle.user_home = "user-home".into();
+    let hash = root.join("user-home/wrapper/dists/gradle-4.10-bin/7ddd1b3f");
+    let gradle = hash.join("gradle-4.10/bin").join(plain);
+    std::fs::create_dir_all(gradle.parent().unwrap()).unwrap();
+    std::fs::write(&gradle, "").unwrap();
+    // Not marked complete: possibly half unpacked.
+    assert_eq!(gradle_command(root, root, &settings), wrapper);
+    std::fs::write(hash.join("gradle-4.10-bin.zip.ok"), "").unwrap();
+    assert_eq!(gradle_command(root, root, &settings), gradle);
+    // With its jar the wrapper runs as usual.
+    std::fs::write(root.join("gradle/wrapper/gradle-wrapper.jar"), "").unwrap();
+    assert_eq!(gradle_command(root, root, &settings), wrapper);
+}
+
 #[test]
 fn gradle_settings_precedence() {
     use crate::apply::{gradle_command, gradle_env};