fix(tasks): warn when due time is ignored by API

.changeset/tasks-due-time-warning.md

@@ -0,0 +1,5 @@
+---
+"@googleworkspace/cli": patch
+---
+
+Warn when a Google Tasks request includes a non-midnight `due` time, since the API stores only the date and ignores time-of-day.

crates/google-workspace-cli/src/executor.rs

@@ -156,6 +156,43 @@ fn parse_and_validate_inputs(
     })
 }
 
+fn extract_due_string_with_non_midnight_time(body: &Value) -> Option<String> {
+    let due = body.get("due")?.as_str()?;
+    let (_, time_part) = due.split_once('T')?;
+    let time_only = match time_part.find(|c: char| c == 'Z' || c == '+' || c == '-') {
+        Some(idx) => &time_part[..idx],
+        None => time_part,
+    };
+
+    if time_only
+        .chars()
+        .any(|c| c.is_ascii_digit() && c != '0')
+    {
+        Some(due.to_string())
+    } else {
+        None
+    }
+}
+
+fn tasks_due_time_truncated_warning(
+    doc: &RestDescription,
+    method: &RestMethod,
+    body: Option<&Value>,
+) -> Option<String> {
+    if doc.name != "tasks" {
+        return None;
+    }
+    if !matches!(method.http_method.as_str(), "POST" | "PUT" | "PATCH") {
+        return None;
+    }
+    let body = body?;
+    let due = extract_due_string_with_non_midnight_time(body)?;
+    Some(format!(
+        "Google Tasks API stores only the due date; time-of-day is ignored (received due='{}').",
+        due
+    ))
+}
+
 /// Build an HTTP request with auth, query params, page token, and body/multipart attachment.
 #[allow(clippy::too_many_arguments)]
 async fn build_http_request(
@@ -413,6 +450,10 @@ pub async fn execute_method(
 ) -> Result<Option<Value>, GwsError> {
     let input = parse_and_validate_inputs(doc, method, params_json, body_json, upload.is_some())?;
 
+    if let Some(msg) = tasks_due_time_truncated_warning(doc, method, input.body.as_ref()) {
+        eprintln!("Warning: {}", sanitize_for_terminal(&msg));
+    }
+
     if dry_run {
         let dry_run_info = json!({
             "dry_run": true,
@@ -1209,6 +1250,70 @@ mod tests {
         assert_ne!(AuthMethod::OAuth, AuthMethod::None);
     }
 
+    #[test]
+    fn tasks_due_time_truncated_warning_detects_non_midnight_due_time() {
+        let doc = RestDescription {
+            name: "tasks".to_string(),
+            ..Default::default()
+        };
+        let method = RestMethod {
+            http_method: "POST".to_string(),
+            ..Default::default()
+        };
+        let body = json!({"due": "2026-04-12T15:30:00.000Z"});
+
+        let warning = tasks_due_time_truncated_warning(&doc, &method, Some(&body));
+        assert!(warning.is_some());
+    }
+
+    #[test]
+    fn tasks_due_time_truncated_warning_ignores_midnight_due_time() {
+        let doc = RestDescription {
+            name: "tasks".to_string(),
+            ..Default::default()
+        };
+        let method = RestMethod {
+            http_method: "PATCH".to_string(),
+            ..Default::default()
+        };
+        let body = json!({"due": "2026-04-12T00:00:00.000Z"});
+
+        let warning = tasks_due_time_truncated_warning(&doc, &method, Some(&body));
+        assert!(warning.is_none());
+    }
+
+    #[test]
+    fn tasks_due_time_truncated_warning_detects_fractional_seconds() {
+        let doc = RestDescription {
+            name: "tasks".to_string(),
+            ..Default::default()
+        };
+        let method = RestMethod {
+            http_method: "PATCH".to_string(),
+            ..Default::default()
+        };
+        let body = json!({"due": "2026-04-12T00:00:00.500Z"});
+
+        let warning = tasks_due_time_truncated_warning(&doc, &method, Some(&body));
+        assert!(warning.is_some());
+    }
+
+    #[test]
+    fn tasks_due_time_truncated_warning_ignores_non_tasks_apis() {
+        let doc = RestDescription {
+            name: "drive".to_string(),
+            ..Default::default()
+        };
+        let method = RestMethod {
+            http_method: "POST".to_string(),
+            ..Default::default()
+        };
+        let body = json!({"due": "2026-04-12T15:30:00.000Z"});
+
+        let warning = tasks_due_time_truncated_warning(&doc, &method, Some(&body));
+        assert!(warning.is_none());
+    }
+
     #[test]
     fn test_mime_to_extension_more_types() {
         assert_eq!(mime_to_extension("text/plain"), "txt");