From 274c9c35cf6a7d93a5bdd96cc10d9f7e504eaa93 Mon Sep 17 00:00:00 2001
From: jk <47693+sectore@users.noreply.github.com>
Date: Tue, 23 Jun 2026 14:25:21 +0200
Subject: [PATCH 1/3] feat: `main` runnables, Stack/Cabal auto-detected

---
 Cargo.lock                      |  42 +++++---
 Cargo.toml                      |   3 +
 languages/haskell/runnables.scm |   9 ++
 languages/haskell/tasks.json    |  24 +++++
 tests/task_verification_test.rs | 169 ++++++++++++++++++++++++++++++++
 5 files changed, 232 insertions(+), 15 deletions(-)
 create mode 100644 languages/haskell/runnables.scm
 create mode 100644 languages/haskell/tasks.json
 create mode 100644 tests/task_verification_test.rs

diff --git a/Cargo.lock b/Cargo.lock
index d727ed3..6ba8eef 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -400,19 +400,13 @@ dependencies = [
 
 [[package]]
 name = "quote"
-version = "1.0.45"
+version = "1.0.46"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "41f2619966050689382d2b44f664f4bc593e129785a36d6ee376ddf37259b924"
+checksum = "dfbc457d0c7a0759a614551b11a6409e5951f6c7537be1f1b7682b9ae9230368"
 dependencies = [
  "proc-macro2",
 ]
 
-[[package]]
-name = "ryu"
-version = "1.0.20"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "28d3b2b1366ec20994f1fd18c3c594f05c5dd4bc44d8bb0c1c632c8d6829481f"
-
 [[package]]
 name = "semver"
 version = "1.0.26"
@@ -424,18 +418,28 @@ dependencies = [
 
 [[package]]
 name = "serde"
-version = "1.0.218"
+version = "1.0.228"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e8dfc9d19bdbf6d17e22319da49161d5d0108e4188e8b680aef6299eed22df60"
+checksum = "9a8e94ea7f378bd32cbbd37198a4a91436180c5bb472411e48b5ec2e2124ae9e"
+dependencies = [
+ "serde_core",
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_core"
+version = "1.0.228"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41d385c7d4ca58e59fc732af25c3983b67ac852c1a25000afe1175de458b67ad"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.218"
+version = "1.0.228"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f09503e191f4e797cb8aac08e9a4a4695c5edf6a2e70e376d961ddd5c969f82b"
+checksum = "d540f220d3187173da220f885ab66608367b6574e925011a9353e4badda91d79"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -444,14 +448,15 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.140"
+version = "1.0.150"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "20068b6e96dc6c9bd23e01df8827e6c7e1f2fddd43c21810382803c136b99373"
+checksum = "e8014e44b4736ed0538adeecded0fce2a272f22dc9578a7eb6b2d9993c74cfb9"
 dependencies = [
  "itoa",
  "memchr",
- "ryu",
  "serde",
+ "serde_core",
+ "zmij",
 ]
 
 [[package]]
@@ -740,6 +745,7 @@ dependencies = [
 name = "zed_haskell"
 version = "0.3.2"
 dependencies = [
+ "serde_json",
  "zed_extension_api",
 ]
 
@@ -796,3 +802,9 @@ dependencies = [
  "quote",
  "syn",
 ]
+
+[[package]]
+name = "zmij"
+version = "1.0.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b8848ee67ecc8aedbaf3e4122217aff892639231befc6a1b58d29fff4c2cabaa"
diff --git a/Cargo.toml b/Cargo.toml
index 2b4f363..8cddda7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,3 +11,6 @@ crate-type = ["cdylib"]
 
 [dependencies]
 zed_extension_api = "0.7.0"
+
+[dev-dependencies]
+serde_json = "1.0.150"
diff --git a/languages/haskell/runnables.scm b/languages/haskell/runnables.scm
new file mode 100644
index 0000000..4393954
--- /dev/null
+++ b/languages/haskell/runnables.scm
@@ -0,0 +1,9 @@
+; Detect the main function
+(declarations
+  [
+    (function name: (variable) @run) @_
+    (bind name: (variable) @run) @_
+  ]
+  (#eq? @run "main")
+  (#set! tag haskell-build)
+  (#set! tag haskell-run))
diff --git a/languages/haskell/tasks.json b/languages/haskell/tasks.json
new file mode 100644
index 0000000..eaf0aa9
--- /dev/null
+++ b/languages/haskell/tasks.json
@@ -0,0 +1,24 @@
+[
+  {
+    "label": "Run",
+    "command": "if [ -f stack.yaml ]; then stack run; elif [ -f cabal.project ] || ls *.cabal 2>/dev/null | grep -q .; then cabal run; else echo 'No Stack or Cabal found to run the code' >&2; exit 1; fi",
+    "tags": ["haskell-run"],
+    "shell": {
+      "with_arguments": {
+        "program": "/bin/sh",
+        "args": ["-c"]
+      }
+    }
+  },
+  {
+    "label": "Build",
+    "command": "if [ -f stack.yaml ]; then stack build; elif [ -f cabal.project ] || ls *.cabal 2>/dev/null | grep -q .; then cabal build; else echo 'No Stack or Cabal found to build the code' >&2; exit 1; fi",
+    "tags": ["haskell-build"],
+    "shell": {
+      "with_arguments": {
+        "program": "/bin/sh",
+        "args": ["-c"]
+      }
+    }
+  }
+]
diff --git a/tests/task_verification_test.rs b/tests/task_verification_test.rs
new file mode 100644
index 0000000..c62815e
--- /dev/null
+++ b/tests/task_verification_test.rs
@@ -0,0 +1,169 @@
+// Heavily inspired by the Java extension's task verification tests:
+// https://github.com/zed-extensions/java/blob/b6b8f9a5396b7f794d12a91ee4c703078ecc3e96/tests/task_verification_test.rs
+
+use serde_json::Value;
+use std::fs;
+use std::path::PathBuf;
+use std::process::Command;
+
+fn get_task_command_by_tag(tag: &str) -> String {
+    let tasks_json =
+        fs::read_to_string("languages/haskell/tasks.json").expect("Failed to read tasks.json");
+    let tasks: Value = serde_json::from_str(&tasks_json).expect("Failed to parse tasks.json");
+    for task in tasks.as_array().expect("tasks.json is not an array") {
+        if let Some(tags) = task["tags"].as_array() {
+            if tags.iter().any(|t| t.as_str() == Some(tag)) {
+                return task["command"]
+                    .as_str()
+                    .expect("command is not a string")
+                    .to_string();
+            }
+        }
+    }
+    panic!("Task with tag '{tag}' not found");
+}
+
+struct TestProject {
+    temp_dir: PathBuf,
+    bin_dir: PathBuf,
+    new_path: String,
+}
+
+impl TestProject {
+    fn new(name: &str) -> Self {
+        let temp_dir = std::env::temp_dir().join(format!("haskell_task_test_{name}"));
+        if temp_dir.exists() {
+            fs::remove_dir_all(&temp_dir).unwrap();
+        }
+        fs::create_dir_all(&temp_dir).unwrap();
+        let bin_dir = temp_dir.join("bin");
+        fs::create_dir_all(&bin_dir).unwrap();
+        let new_path = format!(
+            "{}:{}",
+            bin_dir.to_string_lossy(),
+            std::env::var("PATH").unwrap_or_default()
+        );
+        Self {
+            temp_dir,
+            bin_dir,
+            new_path,
+        }
+    }
+
+    fn with_stack(&self) {
+        fs::File::create(self.temp_dir.join("stack.yaml")).unwrap();
+        fs::File::create(self.temp_dir.join("myproject.cabal")).unwrap();
+        self.mock_bin("stack", "#!/bin/sh\necho \"STACK_CALLED: $@\"");
+    }
+
+    fn with_cabal(&self) {
+        fs::File::create(self.temp_dir.join("myproject.cabal")).unwrap();
+        self.mock_bin("cabal", "#!/bin/sh\necho \"CABAL_CALLED: $@\"");
+    }
+
+    fn with_cabal_project(&self) {
+        fs::File::create(self.temp_dir.join("cabal.project")).unwrap();
+        self.mock_bin("cabal", "#!/bin/sh\necho \"CABAL_CALLED: $@\"");
+    }
+
+    fn mock_bin(&self, name: &str, content: &str) {
+        let bin_path = self.bin_dir.join(name);
+        fs::write(&bin_path, content).unwrap();
+        #[cfg(unix)]
+        {
+            use std::os::unix::fs::PermissionsExt;
+            fs::set_permissions(&bin_path, fs::Permissions::from_mode(0o755)).unwrap();
+        }
+    }
+
+    fn run_task(&self, tag: &str) -> String {
+        let command = get_task_command_by_tag(tag);
+        let output = Command::new("sh")
+            .arg("-c")
+            .arg(&command)
+            .env("PATH", &self.new_path)
+            .current_dir(&self.temp_dir)
+            .output()
+            .expect("Failed to execute shell command");
+        String::from_utf8_lossy(&output.stdout).into_owned()
+            + &String::from_utf8_lossy(&output.stderr)
+    }
+}
+
+impl Drop for TestProject {
+    fn drop(&mut self) {
+        let _ = fs::remove_dir_all(&self.temp_dir);
+    }
+}
+
+#[test]
+fn test_stack_build() {
+    let project = TestProject::new("stack_build");
+    project.with_stack();
+    let output = project.run_task("haskell-build");
+    assert!(output.contains("STACK_CALLED: build"), "Got: {}", output);
+}
+
+#[test]
+fn test_stack_run() {
+    let project = TestProject::new("stack_run");
+    project.with_stack();
+    let output = project.run_task("haskell-run");
+    assert!(output.contains("STACK_CALLED: run"), "Got: {}", output);
+}
+
+#[test]
+fn test_cabal_build() {
+    let project = TestProject::new("cabal_build");
+    project.with_cabal();
+    let output = project.run_task("haskell-build");
+    assert!(output.contains("CABAL_CALLED: build"), "Got: {}", output);
+}
+
+#[test]
+fn test_cabal_run() {
+    let project = TestProject::new("cabal_run");
+    project.with_cabal();
+    let output = project.run_task("haskell-run");
+    assert!(output.contains("CABAL_CALLED: run"), "Got: {}", output);
+}
+
+#[test]
+fn test_cabal_project_build() {
+    let project = TestProject::new("cabal_project_build");
+    project.with_cabal_project();
+    let output = project.run_task("haskell-build");
+    assert!(output.contains("CABAL_CALLED: build"), "Got: {}", output);
+}
+
+#[test]
+fn test_cabal_project_run() {
+    let project = TestProject::new("cabal_project_run");
+    project.with_cabal_project();
+    let output = project.run_task("haskell-run");
+    assert!(output.contains("CABAL_CALLED: run"), "Got: {}", output);
+}
+
+#[test]
+fn test_stack_preferred_over_cabal() {
+    let project = TestProject::new("stack_preferred");
+    project.with_stack();
+    project.with_cabal();
+    let output = project.run_task("haskell-run");
+    assert!(
+        output.contains("STACK_CALLED: run"),
+        "Stack should be preferred when stack.yaml present. Got: {}",
+        output
+    );
+}
+
+#[test]
+fn test_no_build_tool() {
+    let project = TestProject::new("no_tool");
+    let output = project.run_task("haskell-build");
+    assert!(
+        output.contains("No Stack or Cabal found"),
+        "Got: {}",
+        output
+    );
+}

From 4690e2279a6506dab90e5e7a475d261861e26735 Mon Sep 17 00:00:00 2001
From: jk <47693+sectore@users.noreply.github.com>
Date: Thu, 25 Jun 2026 08:37:37 +0200
Subject: [PATCH 2/3] hide output of spawned tasks

see https://zed.dev/docs/tasks?highlight=tasks#tasks
---
 languages/haskell/tasks.json | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/languages/haskell/tasks.json b/languages/haskell/tasks.json
index eaf0aa9..58d86e7 100644
--- a/languages/haskell/tasks.json
+++ b/languages/haskell/tasks.json
@@ -8,7 +8,8 @@
         "program": "/bin/sh",
         "args": ["-c"]
       }
-    }
+    },
+    "show_command": false
   },
   {
     "label": "Build",
@@ -19,6 +20,7 @@
         "program": "/bin/sh",
         "args": ["-c"]
       }
-    }
+    },
+    "show_command": false
   }
 ]

From c7531aaac4508f715f448e3b70c787b8640893e4 Mon Sep 17 00:00:00 2001
From: jk <47693+sectore@users.noreply.github.com>
Date: Thu, 25 Jun 2026 08:38:40 +0200
Subject: [PATCH 3/3] run Zed's `tree-sitter-query` extension

to format / lint
---
 languages/haskell/runnables.scm | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/languages/haskell/runnables.scm b/languages/haskell/runnables.scm
index 4393954..7b9959d 100644
--- a/languages/haskell/runnables.scm
+++ b/languages/haskell/runnables.scm
@@ -1,8 +1,10 @@
 ; Detect the main function
 (declarations
   [
-    (function name: (variable) @run) @_
-    (bind name: (variable) @run) @_
+    (function
+      name: (variable) @run)
+    (bind
+      name: (variable) @run)
   ]
   (#eq? @run "main")
   (#set! tag haskell-build)