fix: Recompute eager hashing flag after prepending global inputs

crates/turborepo-engine/src/task_definition.rs

@@ -177,6 +177,7 @@ pub fn prepend_global_inputs(
         .collect();
     global_globs.append(&mut inputs.globs);
     inputs.globs = global_globs;
+    inputs.eager = true;
 }
 
 #[cfg(test)]
@@ -213,6 +214,54 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_prepend_global_inputs_marks_jit_only_task_eager() {
+        let path_to_root = RelativeUnixPathBuf::new("../..").expect("valid path");
+        let mut inputs = TaskInputs {
+            globs: vec![],
+            default: false,
+            jit_globs: vec!["src/**".to_string()],
+            jit_default: false,
+            eager: false,
+            ..Default::default()
+        };
+
+        prepend_global_inputs(
+            &mut inputs,
+            true,
+            &["config.txt".to_string()],
+            &path_to_root,
+        );
+
+        assert_eq!(inputs.globs, vec!["../../config.txt"]);
+        assert!(
+            inputs.eager,
+            "task is no longer jit only once global inputs are prepended, so the eager pass has \
+             to run or those globs never get hashed"
+        );
+    }
+
+    #[test]
+    fn test_prepend_global_inputs_leaves_jit_only_task_alone_without_global_inputs() {
+        let path_to_root = RelativeUnixPathBuf::new("../..").expect("valid path");
+        let mut inputs = TaskInputs {
+            globs: vec![],
+            default: false,
+            jit_globs: vec!["src/**".to_string()],
+            jit_default: false,
+            eager: false,
+            ..Default::default()
+        };
+
+        prepend_global_inputs(&mut inputs, true, &[], &path_to_root);
+
+        assert!(inputs.globs.is_empty());
+        assert!(
+            !inputs.eager,
+            "a task that is still jit only should not start hashing eagerly"
+        );
+    }
+
     #[test]
     fn test_prepend_global_inputs_sets_default_when_no_explicit_inputs() {
         let path_to_root = RelativeUnixPathBuf::new("../..").expect("valid path");

crates/turborepo/tests/global_inputs_test.rs

@@ -29,6 +29,20 @@ const TURBO_JSON_GLOBAL_INPUTS: &str = r#"{
 }
 "#;
 
+const TURBO_JSON_GLOBAL_INPUTS_JIT: &str = r#"{
+  "futureFlags": { "globalConfiguration": true },
+  "global": {
+    "inputs": ["config.txt"]
+  },
+  "tasks": {
+    "build": {
+      "inputs": [{ "mode": "jit", "globs": ["src/**"] }],
+      "outputs": []
+    }
+  }
+}
+"#;
+
 const TURBO_JSON_GLOBAL_INPUTS_TOPO: &str = r#"{
   "futureFlags": { "globalConfiguration": true },
   "global": {
@@ -282,3 +296,46 @@ fn test_global_inputs_exclusion_not_defeated_by_phantom_dependency_tasks() {
         "expected app-b cache hit (phantom dep should not defeat negation), got: {combined}"
     );
 }
+
+/// A task whose only `inputs` are JIT still has `global.inputs` prepended to
+/// its eager globs, so a change to a global input file must invalidate it.
+#[test]
+fn test_global_inputs_invalidate_jit_only_task() {
+    let tempdir = tempfile::tempdir().unwrap();
+    setup_fixture(tempdir.path(), TURBO_JSON_GLOBAL_INPUTS_JIT);
+
+    let output = run_turbo(
+        tempdir.path(),
+        &["build", "-F", "app-a", "--output-logs=hash-only"],
+    );
+    assert!(output.status.success());
+    let combined = combined_output(&output);
+    assert!(
+        combined.contains("cache miss"),
+        "expected cache miss on first run, got: {combined}"
+    );
+
+    let output = run_turbo(
+        tempdir.path(),
+        &["build", "-F", "app-a", "--output-logs=hash-only"],
+    );
+    assert!(output.status.success());
+    let combined = combined_output(&output);
+    assert!(
+        combined.contains("cache hit"),
+        "expected cache hit on second run, got: {combined}"
+    );
+
+    fs::write(tempdir.path().join("config.txt"), "changed value").unwrap();
+
+    let output = run_turbo(
+        tempdir.path(),
+        &["build", "-F", "app-a", "--output-logs=hash-only"],
+    );
+    assert!(output.status.success());
+    let combined = combined_output(&output);
+    assert!(
+        combined.contains("cache miss"),
+        "expected cache miss after changing a global input, got: {combined}"
+    );
+}