#237 fix: give auto temporal columns a database default in migrations

README.md

@@ -220,7 +220,7 @@ tracing-subscriber = "0.3"
 
 ```rust,ignore
 #[id]                          // Primary key (auto-generated UUID)
-#[auto]                        // Auto-generated (timestamps)
+#[auto]                        // Auto-generated: skipped by INSERT, gets a DB default in migrations
 #[owner]                       // Ownership column: adds *_scoped methods
 #[version]                     // Optimistic locking: guarded, auto-bumped
 #[embed(prefix, fields(...))]  // Flatten a value object to prefixed columns

crates/entity-derive-impl/src/entity/migrations/postgres/ddl.rs

@@ -8,7 +8,7 @@
 use convert_case::{Case, Casing};
 
 use crate::entity::{
-    migrations::types::{PostgresTypeMapper, TypeMapper},
+    migrations::types::{PostgresTypeMapper, SqlType, TypeMapper},
     parse::{CompositeIndexDef, EntityDef, FieldDef}
 };
 
@@ -96,9 +96,13 @@ fn generate_column_def(
         parts.push("UNIQUE".to_string());
     }
 
-    // DEFAULT value
+    // DEFAULT value: explicit declaration wins, otherwise an #[auto]
+    // temporal column gets the default that makes the generated INSERT
+    // (which skips auto columns) valid.
     if let Some(ref default) = field.column().default {
         parts.push(format!("DEFAULT {default}"));
+    } else if let Some(default) = implicit_auto_default(field, &sql_type) {
+        parts.push(format!("DEFAULT {default}"));
     }
 
     // CHECK constraint
@@ -124,6 +128,26 @@ fn generate_column_def(
     parts.join(" ")
 }
 
+/// Database-side default for an `#[auto]` column that carries no
+/// explicit `#[column(default = ...)]`.
+///
+/// The generated INSERT skips `#[auto]` columns, so a `NOT NULL` one
+/// without a default rejects every row. Temporal columns get the clock
+/// function matching their type; anything else keeps no default, since
+/// the macro has no meaningful value to invent.
+fn implicit_auto_default(field: &FieldDef, sql_type: &SqlType) -> Option<&'static str> {
+    if !field.is_auto() || sql_type.nullable || sql_type.array_dim > 0 {
+        return None;
+    }
+
+    match sql_type.name.as_str() {
+        "TIMESTAMPTZ" | "TIMESTAMP" => Some("NOW()"),
+        "DATE" => Some("CURRENT_DATE"),
+        "TIME" | "TIMETZ" => Some("CURRENT_TIME"),
+        _ => None
+    }
+}
+
 /// Generate CREATE INDEX for a single column.
 fn generate_single_index(entity: &EntityDef, field: &FieldDef) -> String {
     let table = entity.table.clone();
@@ -282,6 +306,74 @@ mod tests {
         assert!(sql.contains("email TEXT NOT NULL UNIQUE"));
     }
 
+    #[test]
+    fn auto_temporal_columns_get_a_clock_default() {
+        let entity = parse_entity(quote::quote! {
+            #[entity(table = "users", migrations)]
+            pub struct User {
+                #[id]
+                pub id: uuid::Uuid,
+                #[field(response)]
+                #[auto]
+                pub created_at: chrono::DateTime<chrono::Utc>,
+                #[field(response)]
+                #[auto]
+                pub born_on: chrono::NaiveDate,
+                #[field(response)]
+                #[auto]
+                pub rings_at: chrono::NaiveTime,
+            }
+        });
+        let sql = generate_up(&entity);
+        assert!(
+            sql.contains("created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()"),
+            "the generated INSERT skips auto columns, so the DDL must supply the value: {sql}"
+        );
+        assert!(sql.contains("born_on DATE NOT NULL DEFAULT CURRENT_DATE"));
+        assert!(sql.contains("rings_at TIME NOT NULL DEFAULT CURRENT_TIME"));
+    }
+
+    #[test]
+    fn explicit_default_wins_over_the_implicit_one() {
+        let entity = parse_entity(quote::quote! {
+            #[entity(table = "users", migrations)]
+            pub struct User {
+                #[id]
+                pub id: uuid::Uuid,
+                #[field(response)]
+                #[auto]
+                #[column(default = "'epoch'")]
+                pub created_at: chrono::DateTime<chrono::Utc>,
+            }
+        });
+        let sql = generate_up(&entity);
+        assert!(sql.contains("created_at TIMESTAMPTZ NOT NULL DEFAULT 'epoch'"));
+        assert!(!sql.contains("NOW()"));
+    }
+
+    #[test]
+    fn non_temporal_and_nullable_auto_columns_keep_no_default() {
+        let entity = parse_entity(quote::quote! {
+            #[entity(table = "users", migrations)]
+            pub struct User {
+                #[id]
+                pub id: uuid::Uuid,
+                #[field(response)]
+                #[auto]
+                pub token: String,
+                #[field(response)]
+                #[auto]
+                pub seen_at: Option<chrono::DateTime<chrono::Utc>>,
+            }
+        });
+        let sql = generate_up(&entity);
+        assert!(sql.contains("token TEXT NOT NULL,"));
+        assert!(
+            !sql.contains("seen_at TIMESTAMPTZ DEFAULT"),
+            "a nullable auto column already accepts the absent value: {sql}"
+        );
+    }
+
     #[test]
     fn generate_up_with_default() {
         let entity = parse_entity(quote::quote! {

crates/entity-derive/tests/postgres.rs

@@ -51,11 +51,10 @@ mod articles {
         #[filter(range)]
         pub views: i64,
 
-        /// Populated by the database default: the generated INSERT skips
-        /// `#[auto]` columns, so the DDL has to supply the value.
+        /// Populated by the database: the generated INSERT skips
+        /// `#[auto]` columns, so the DDL supplies the value.
         #[field(response)]
         #[auto]
-        #[column(default = "NOW()")]
         pub created_at: DateTime<Utc>
     }
 

wiki/Atributos.md

@@ -340,6 +340,11 @@ Marca campos auto-generados (timestamps, secuencias).
 - Obtiene `Default::default()` en `From<CreateRequest>`
 - Excluido de `CreateRequest` y `UpdateRequest`
 - Puede incluirse en `Response` con `#[field(response)]`
+- Excluido del `INSERT` generado, por lo que con `migrations` una
+  columna temporal no nulable recibe el valor por defecto correspondiente
+  en la base de datos: `NOW()` para `TIMESTAMPTZ` y `TIMESTAMP`,
+  `CURRENT_DATE` para `DATE`, `CURRENT_TIME` para `TIME`. Un
+  `#[column(default = "...")]` explícito tiene prioridad
 
 ```rust
 #[auto]

wiki/Attributes-en.md

@@ -399,6 +399,11 @@ Marks auto-generated fields (timestamps, sequences).
 - Gets `Default::default()` in `From<CreateRequest>`
 - Excluded from `CreateRequest` and `UpdateRequest`
 - Can be included in `Response` with `#[field(response)]`
+- Excluded from the generated `INSERT`, so with `migrations` a
+  non-nullable temporal column receives a matching database default:
+  `NOW()` for `TIMESTAMPTZ` and `TIMESTAMP`, `CURRENT_DATE` for `DATE`,
+  `CURRENT_TIME` for `TIME`. An explicit `#[column(default = "...")]`
+  overrides it
 
 ```rust
 #[auto]

wiki/Атрибуты.md

@@ -399,6 +399,11 @@ pub id: Uuid,
 - Получает `Default::default()` в `From<CreateRequest>`
 - Исключается из `CreateRequest` и `UpdateRequest`
 - Может включаться в `Response` с `#[field(response)]`
+- Исключается из генерируемого `INSERT`, поэтому с `migrations`
+  non-nullable колонка с временным типом получает соответствующий
+  default в БД: `NOW()` для `TIMESTAMPTZ` и `TIMESTAMP`, `CURRENT_DATE`
+  для `DATE`, `CURRENT_TIME` для `TIME`. Явный
+  `#[column(default = "...")]` имеет приоритет
 
 ```rust
 #[auto]

wiki/属性.md

@@ -340,6 +340,10 @@ pub id: Uuid,
 - 在 `From<CreateRequest>` 中获取 `Default::default()`
 - 从 `CreateRequest` 和 `UpdateRequest` 中排除
 - 可通过 `#[field(response)]` 包含在 `Response` 中
+- 从生成的 `INSERT` 中排除，因此启用 `migrations` 时，非空的时间类型列
+  会获得相应的数据库默认值：`TIMESTAMPTZ` 和 `TIMESTAMP` 为 `NOW()`，
+  `DATE` 为 `CURRENT_DATE`，`TIME` 为 `CURRENT_TIME`。显式的
+  `#[column(default = "...")]` 优先
 
 ```rust
 #[auto]

wiki/속성.md

@@ -340,6 +340,11 @@ pub id: Uuid,
 - `From<CreateRequest>`에서 `Default::default()` 획득
 - `CreateRequest`와 `UpdateRequest`에서 제외
 - `#[field(response)]`로 `Response`에 포함 가능
+- 생성된 `INSERT`에서 제외되므로 `migrations` 사용 시 NULL을 허용하지
+  않는 시간 계열 컬럼은 해당하는 데이터베이스 기본값을 받습니다:
+  `TIMESTAMPTZ`와 `TIMESTAMP`는 `NOW()`, `DATE`는 `CURRENT_DATE`,
+  `TIME`은 `CURRENT_TIME`. 명시적인 `#[column(default = "...")]`이
+  우선합니다
 
 ```rust
 #[auto]