feat: expose SQL Server metadata comments

src/driver/introspection.rs

@@ -18,9 +18,16 @@ use std::collections::HashMap;
 // --- SQL query constants --------------------------------------------------
 
 pub const Q_GET_TABLES: &str = "\
-SELECT t.name \
+SELECT \
+    t.name, \
+    TRY_CONVERT(nvarchar(max), ep.value) AS comment \
 FROM sys.tables t \
 JOIN sys.schemas s ON t.schema_id = s.schema_id \
+LEFT JOIN sys.extended_properties ep \
+    ON ep.class = 1 \
+    AND ep.major_id = t.object_id \
+    AND ep.minor_id = 0 \
+    AND ep.name = N'MS_Description' \
 WHERE s.name = @P1 \
 ORDER BY t.name";
 
@@ -49,12 +56,18 @@ SELECT \
           AND ic.column_id = c.column_id \
           AND i.is_primary_key = 1 \
     ), 0) AS BIT) AS is_pk, \
-    dc.definition AS default_value \
+    dc.definition AS default_value, \
+    TRY_CONVERT(nvarchar(max), ep.value) AS comment \
 FROM sys.columns c \
 JOIN sys.types ty ON c.user_type_id = ty.user_type_id \
 LEFT JOIN sys.default_constraints dc \
     ON dc.parent_object_id = c.object_id \
     AND dc.parent_column_id = c.column_id \
+LEFT JOIN sys.extended_properties ep \
+    ON ep.class = 1 \
+    AND ep.major_id = c.object_id \
+    AND ep.minor_id = c.column_id \
+    AND ep.name = N'MS_Description' \
 WHERE c.object_id = OBJECT_ID(@P1) \
 ORDER BY c.column_id";
 
@@ -204,14 +217,20 @@ SELECT \
           AND ic.column_id = c.column_id \
           AND i.is_primary_key = 1 \
     ), 0) AS BIT) AS is_pk, \
-    dc.definition AS default_value \
+    dc.definition AS default_value, \
+    TRY_CONVERT(nvarchar(max), ep.value) AS comment \
 FROM sys.columns c \
 JOIN sys.tables t ON c.object_id = t.object_id \
 JOIN sys.schemas s ON t.schema_id = s.schema_id \
 JOIN sys.types ty ON c.user_type_id = ty.user_type_id \
 LEFT JOIN sys.default_constraints dc \
     ON dc.parent_object_id = c.object_id \
     AND dc.parent_column_id = c.column_id \
+LEFT JOIN sys.extended_properties ep \
+    ON ep.class = 1 \
+    AND ep.major_id = c.object_id \
+    AND ep.minor_id = c.column_id \
+    AND ep.name = N'MS_Description' \
 WHERE s.name = @P1 \
 ORDER BY t.name, c.column_id";
 
@@ -369,6 +388,7 @@ pub fn build_table_column(
     max_length_bytes: i32,
     is_pk: bool,
     default_value: Option<String>,
+    comment: Option<String>,
 ) -> TableColumn {
     let character_maximum_length = if is_string_type(&data_type) {
         character_length_from_sys_columns(&data_type, max_length_bytes)
@@ -384,6 +404,7 @@ pub fn build_table_column(
         is_generated,
         default_value,
         character_maximum_length,
+        comment,
     }
 }
 
@@ -474,8 +495,9 @@ pub async fn get_tables(
     Ok(rows
         .into_iter()
         .filter_map(|r| {
-            r.get::<&str, _>(0).map(|n| TableInfo {
+            r.get::<&str, _>("name").map(|n| TableInfo {
                 name: n.to_string(),
+                comment: row_str_opt(&r, "comment"),
             })
         })
         .collect())
@@ -505,6 +527,7 @@ pub async fn get_columns(
                 row_i32(&r, "max_length"),
                 row_bool(&r, "is_pk"),
                 row_str_opt(&r, "default_value"),
+                row_str_opt(&r, "comment"),
             )
         })
         .collect())
@@ -597,6 +620,7 @@ pub async fn get_all_columns_batch(
             row_i32(&r, "max_length"),
             row_bool(&r, "is_pk"),
             row_str_opt(&r, "default_value"),
+            row_str_opt(&r, "comment"),
         );
         out.entry(table_name).or_default().push(col);
     }

src/driver/introspection/tests.rs

@@ -3,9 +3,15 @@ use super::*;
 // --- Query shape assertions (no live server needed) -------------------
 
 #[test]
-fn q_get_tables_queries_sys_tables_and_schemas() {
+fn q_get_tables_queries_descriptions_with_object_scope() {
     assert!(Q_GET_TABLES.contains("sys.tables"));
     assert!(Q_GET_TABLES.contains("sys.schemas"));
+    assert!(Q_GET_TABLES.contains("sys.extended_properties ep"));
+    assert!(Q_GET_TABLES.contains("ep.class = 1"));
+    assert!(Q_GET_TABLES.contains("ep.major_id = t.object_id"));
+    assert!(Q_GET_TABLES.contains("ep.minor_id = 0"));
+    assert!(Q_GET_TABLES.contains("ep.name = N'MS_Description'"));
+    assert!(Q_GET_TABLES.contains("TRY_CONVERT(nvarchar(max), ep.value) AS comment"));
     assert!(Q_GET_TABLES.contains("@P1"));
     assert!(Q_GET_TABLES.contains("ORDER BY t.name"));
 }
@@ -18,6 +24,12 @@ fn q_get_columns_joins_sys_types_and_reports_pk() {
     assert!(Q_GET_COLUMNS.contains("sys.indexes"));
     assert!(Q_GET_COLUMNS.contains("is_primary_key"));
     assert!(Q_GET_COLUMNS.contains("sys.default_constraints"));
+    assert!(Q_GET_COLUMNS.contains("sys.extended_properties ep"));
+    assert!(Q_GET_COLUMNS.contains("ep.class = 1"));
+    assert!(Q_GET_COLUMNS.contains("ep.major_id = c.object_id"));
+    assert!(Q_GET_COLUMNS.contains("ep.minor_id = c.column_id"));
+    assert!(Q_GET_COLUMNS.contains("ep.name = N'MS_Description'"));
+    assert!(Q_GET_COLUMNS.contains("TRY_CONVERT(nvarchar(max), ep.value) AS comment"));
     assert!(Q_GET_COLUMNS.contains("c.is_computed AS is_generated"));
     assert!(Q_GET_COLUMNS.contains("OBJECT_ID(@P1)"));
     assert!(Q_GET_COLUMNS.contains("ORDER BY c.column_id"));
@@ -150,6 +162,12 @@ fn q_get_all_columns_batch_groups_by_table() {
     assert!(Q_GET_ALL_COLUMNS_BATCH.contains("sys.tables"));
     assert!(Q_GET_ALL_COLUMNS_BATCH.contains("sys.schemas"));
     assert!(Q_GET_ALL_COLUMNS_BATCH.contains("sys.types"));
+    assert!(Q_GET_ALL_COLUMNS_BATCH.contains("sys.extended_properties ep"));
+    assert!(Q_GET_ALL_COLUMNS_BATCH.contains("ep.class = 1"));
+    assert!(Q_GET_ALL_COLUMNS_BATCH.contains("ep.major_id = c.object_id"));
+    assert!(Q_GET_ALL_COLUMNS_BATCH.contains("ep.minor_id = c.column_id"));
+    assert!(Q_GET_ALL_COLUMNS_BATCH.contains("ep.name = N'MS_Description'"));
+    assert!(Q_GET_ALL_COLUMNS_BATCH.contains("TRY_CONVERT(nvarchar(max), ep.value) AS comment"));
     assert!(Q_GET_ALL_COLUMNS_BATCH.contains("@P1"));
     assert!(Q_GET_ALL_COLUMNS_BATCH.contains("ORDER BY t.name, c.column_id"));
     // Must emit the table name so the caller can group rows.
@@ -194,6 +212,7 @@ fn build_table_column_populates_string_length() {
         40,
         false,
         None,
+        None,
     );
     assert_eq!(col.name, "note");
     assert_eq!(col.data_type, "nvarchar");
@@ -206,7 +225,17 @@ fn build_table_column_populates_string_length() {
 
 #[test]
 fn build_table_column_leaves_length_none_for_numeric() {
-    let col = build_table_column("id".into(), "int".into(), false, true, false, 4, true, None);
+    let col = build_table_column(
+        "id".into(),
+        "int".into(),
+        false,
+        true,
+        false,
+        4,
+        true,
+        None,
+        None,
+    );
     assert_eq!(col.character_maximum_length, None);
     assert!(col.is_pk);
     assert!(col.is_auto_increment);
@@ -224,6 +253,7 @@ fn build_table_column_honours_max_as_none() {
         -1,
         false,
         None,
+        None,
     );
     assert_eq!(col.character_maximum_length, None);
 }
@@ -239,6 +269,7 @@ fn build_table_column_carries_default_value() {
         8,
         false,
         Some("(getdate())".into()),
+        None,
     );
     assert_eq!(col.default_value, Some("(getdate())".into()));
     assert_eq!(col.character_maximum_length, None);
@@ -255,11 +286,62 @@ fn build_table_column_reports_generated_and_parameterized_lengths() {
         84,
         false,
         None,
+        None,
     );
     assert!(col.is_generated);
     assert_eq!(col.character_maximum_length, Some(42));
 }
 
+#[test]
+fn metadata_descriptions_serialize_verbatim_and_omit_absent_values() {
+    let comment = "Owner's résumé\n次の行";
+    let table = TableInfo {
+        name: "notes".into(),
+        comment: Some(comment.into()),
+    };
+    let table_json = serde_json::to_value(&table).expect("serialize table metadata");
+    assert_eq!(table_json["comment"], comment);
+
+    let plain_table = TableInfo {
+        name: "plain".into(),
+        comment: None,
+    };
+    let plain_table_json =
+        serde_json::to_value(&plain_table).expect("serialize table metadata without comment");
+    assert!(plain_table_json.get("comment").is_none());
+
+    let col = build_table_column(
+        "note".into(),
+        "nvarchar(100)".into(),
+        true,
+        false,
+        false,
+        200,
+        false,
+        None,
+        Some(comment.into()),
+    );
+    assert_eq!(col.comment.as_deref(), Some(comment));
+
+    let json = serde_json::to_value(&col).expect("serialize column metadata");
+    assert_eq!(json["comment"], comment);
+
+    let plain_col = build_table_column(
+        "plain".into(),
+        "int".into(),
+        true,
+        false,
+        false,
+        4,
+        false,
+        None,
+        None,
+    );
+    let plain_col_json =
+        serde_json::to_value(&plain_col).expect("serialize column metadata without comment");
+    assert!(plain_col_json.get("comment").is_none());
+}
+
 // --- build_foreign_keys ----------------------------------------------
 
 #[test]

src/models.rs

@@ -67,6 +67,8 @@ pub struct ConnectionParams {
 #[derive(Debug, Serialize, Deserialize)]
 pub struct TableInfo {
     pub name: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub comment: Option<String>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
@@ -82,6 +84,8 @@ pub struct TableColumn {
     pub default_value: Option<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub character_maximum_length: Option<u64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub comment: Option<String>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]

tests/conformance.rs

@@ -2,7 +2,7 @@
 //!
 //! The model definitions below are copied verbatim from
 //! `tabularis/src-tauri/src/models.rs` at host commit
-//! `ba0463d3b861ec8fad110126c67e3fc12bac9839`. Re-sync them and regenerate
+//! `3f0780e19191b3d6721ba7e5d8c1224fb8f4e8fe`. Re-sync them and regenerate
 //! `tests/fixtures/conformance/` with `python3 tests/capture_conformance.py`
 //! whenever the host models or plugin RPC surface changes.
 
@@ -20,6 +20,8 @@ use serde_json::Value;
 #[derive(Debug, Serialize, Deserialize)]
 pub struct TableInfo {
     pub name: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub comment: Option<String>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
@@ -35,6 +37,8 @@ pub struct TableColumn {
     pub default_value: Option<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub character_maximum_length: Option<u64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub comment: Option<String>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
@@ -378,7 +382,23 @@ fn drift_prone_wire_fields_are_exercised() {
         .is_some());
     assert!(batch[1].error.is_some());
 
+    let tables: Vec<TableInfo> = serde_json::from_value(fixture_result("get_tables")).unwrap();
+    assert!(tables.iter().all(|table| table.comment.is_none()));
+    let mut commented_table = fixture_result("get_tables")[0].clone();
+    commented_table["comment"] = Value::String("Owner's résumé\n次の行".into());
+    let commented_table: TableInfo = serde_json::from_value(commented_table).unwrap();
+    assert_eq!(
+        commented_table.comment.as_deref(),
+        Some("Owner's résumé\n次の行")
+    );
+
     let columns: Vec<TableColumn> = serde_json::from_value(fixture_result("get_columns")).unwrap();
+    assert!(columns.iter().all(|column| column.comment.is_none()));
+    let mut commented_column = fixture_result("get_columns")[0].clone();
+    commented_column["comment"] = Value::String("L'état naïve\nΔ".into());
+    let commented_column: TableColumn = serde_json::from_value(commented_column).unwrap();
+    assert_eq!(commented_column.comment.as_deref(), Some("L'état naïve\nΔ"));
+
     let label = columns
         .iter()
         .find(|column| column.name == "label")