scythe-codegen 0.20.2

use scythe_backend::manifest::BackendManifest;
use scythe_backend::naming::{composite_type_name, enum_type_name, enum_variant_name, fn_name, to_snake_case};
use scythe_backend::types::resolve_type;
use std::fmt::Write;

use scythe_core::analyzer::{AnalyzedQuery, CompositeInfo, EnumInfo};
use scythe_core::errors::{ErrorCode, ScytheError};
use scythe_core::parser::QueryCommand;

use crate::backend_options::reject_unknown_options;
use crate::backend_trait::{CodegenBackend, ResolvedColumn, ResolvedParam};
use crate::backends::typescript_common::parse_bool_option;

const DEFAULT_MANIFEST_TOML: &str = include_str!("../../manifests/rust-tiberius.toml");

pub struct RustTiberiusBackend {
    manifest: BackendManifest,
    /// When true, every generated struct/enum derives `serde::Serialize` and
    /// `serde::Deserialize` in addition to its base derives. Set via the
    /// `serde` backend option -- see [`Self::apply_options`].
    serde: bool,
    /// Extra derive macros appended after the base derives (and after serde,
    /// when enabled) on every generated struct/enum. Set via the `derive`
    /// backend option -- see [`Self::apply_options`].
    extra_derives: Vec<String>,
}

impl RustTiberiusBackend {
    pub fn new(engine: &str) -> Result<Self, ScytheError> {
        match engine {
            "mssql" => {}
            _ => {
                return Err(ScytheError::new(
                    ErrorCode::InvalidConfig,
                    format!("rust-tiberius only supports MSSQL, got engine '{}'", engine),
                ));
            }
        }
        let manifest = super::parse_manifest(DEFAULT_MANIFEST_TOML)?;
        Ok(Self {
            manifest,
            serde: false,
            extra_derives: Vec::new(),
        })
    }

    /// Build the derive line for structs, incorporating serde and extra derives.
    fn struct_derives(&self) -> String {
        let mut derives = vec!["Debug", "Clone"];
        if self.serde {
            derives.push("serde::Serialize");
            derives.push("serde::Deserialize");
        }
        for d in &self.extra_derives {
            derives.push(d);
        }
        format!("#[derive({})]", derives.join(", "))
    }

    /// Build the derive line for enums (includes PartialEq, Eq, matching tokio-postgres).
    fn enum_derives(&self) -> String {
        let mut derives = vec!["Debug", "Clone", "PartialEq", "Eq"];
        if self.serde {
            derives.push("serde::Serialize");
            derives.push("serde::Deserialize");
        }
        for d in &self.extra_derives {
            derives.push(d);
        }
        format!("#[derive({})]", derives.join(", "))
    }

    /// Generate the struct-field initializer expression for a tiberius row column.
    /// Used inside `from_row` implementations: `field_name: <expr>,`.
    fn tiberius_field_init(col: &ResolvedColumn) -> String {
        if col.nullable {
            if col.neutral_type == "string" {
                format!(
                    "{}: row.try_get::<&str, _>(\"{}\")?.map(|s| s.to_string())",
                    col.field_name, col.name
                )
            } else {
                format!("{}: row.try_get(\"{}\")?", col.field_name, col.name)
            }
        } else if col.neutral_type == "string" {
            format!(
                "{}: row.try_get::<&str, _>(\"{name}\")?.ok_or_else(|| tiberius::error::Error::Protocol(\"unexpected NULL for non-nullable column '{name}'\".into()))?.to_string()",
                col.field_name,
                name = col.name
            )
        } else {
            format!(
                "{}: row.try_get(\"{name}\")?.ok_or_else(|| tiberius::error::Error::Protocol(\"unexpected NULL for non-nullable column '{name}'\".into()))?",
                col.field_name,
                name = col.name
            )
        }
    }

    /// Generate the right-hand side expression for decoding a column from a tiberius row.
    /// Used as a standalone `let field: Type = <expr>;` statement.
    fn tiberius_decode_col(col: &ResolvedColumn) -> String {
        if col.nullable {
            if col.neutral_type == "string" {
                format!("row.try_get::<&str, _>(\"{}\")?.map(|s| s.to_string())", col.name)
            } else {
                format!("row.try_get(\"{}\")?", col.name)
            }
        } else if col.neutral_type == "string" {
            format!(
                "row.try_get::<&str, _>(\"{name}\")?.ok_or_else(|| tiberius::error::Error::Protocol(\"unexpected NULL for non-nullable column '{name}'\".into()))?.to_string()",
                name = col.name
            )
        } else {
            format!(
                "row.try_get(\"{name}\")?.ok_or_else(|| tiberius::error::Error::Protocol(\"unexpected NULL for non-nullable column '{name}'\".into()))?",
                name = col.name
            )
        }
    }
}

/// Rewrite $1, $2, ... positional params to @p1, @p2, ... for MSSQL.
impl CodegenBackend for RustTiberiusBackend {
    fn name(&self) -> &str {
        "rust-tiberius"
    }

    fn manifest(&self) -> &scythe_backend::manifest::BackendManifest {
        &self.manifest
    }

    fn manifest_mut(&mut self) -> &mut scythe_backend::manifest::BackendManifest {
        &mut self.manifest
    }

    fn supported_engines(&self) -> &[&str] {
        &["mssql"]
    }

    fn file_header(&self) -> String {
        "#![allow(dead_code, unused_imports, clippy::all)]".to_string()
    }

    fn apply_options(&mut self, options: &std::collections::HashMap<String, String>) -> Result<(), ScytheError> {
        reject_unknown_options(&["serde", "derive"], options)?;

        if let Some(val) = options.get("serde") {
            self.serde = parse_bool_option("serde", val)?;
        }
        if let Some(val) = options.get("derive") {
            self.extra_derives = val.split(',').map(|s| s.trim().to_string()).collect();
        }
        Ok(())
    }

    fn generate_struct_decl(
        &self,
        struct_name: &str,
        _query_name: &str,
        columns: &[ResolvedColumn],
    ) -> Result<String, ScytheError> {
        let mut out = String::new();

        let _ = writeln!(out, "{}", self.struct_derives());
        let _ = writeln!(out, "pub struct {} {{", struct_name);
        for col in columns {
            let _ = writeln!(out, "    pub {}: {},", col.field_name, col.full_type);
        }
        let _ = writeln!(out, "}}");
        let _ = writeln!(out);

        let _ = writeln!(out, "impl {} {{", struct_name);
        let _ = writeln!(
            out,
            "    pub fn from_row(row: &tiberius::Row) -> Result<Self, tiberius::error::Error> {{"
        );
        let _ = writeln!(out, "        Ok(Self {{");
        for col in columns {
            if col.nullable {
                if col.neutral_type == "string" {
                    let _ = writeln!(
                        out,
                        "            {}: row.try_get::<&str, _>(\"{}\")?.map(|s| s.to_string()),",
                        col.field_name, col.name
                    );
                } else {
                    let _ = writeln!(out, "            {}: row.try_get(\"{}\")?,", col.field_name, col.name);
                }
            } else {
                if col.neutral_type == "string" {
                    let _ = writeln!(
                        out,
                        "            {}: row.try_get::<&str, _>(\"{}\")?.ok_or_else(|| tiberius::error::Error::Protocol(\"unexpected NULL for non-nullable column '{}'\".into()))?.to_string(),",
                        col.field_name, col.name, col.name
                    );
                } else {
                    let _ = writeln!(
                        out,
                        "            {}: row.try_get(\"{}\")?.ok_or_else(|| tiberius::error::Error::Protocol(\"unexpected NULL for non-nullable column '{}'\".into()))?,",
                        col.field_name, col.name, col.name
                    );
                }
            }
        }
        let _ = writeln!(out, "        }})");
        let _ = writeln!(out, "    }}");
        let _ = write!(out, "}}");

        Ok(out)
    }

    fn generate_query_fn(
        &self,
        analyzed: &AnalyzedQuery,
        struct_name: &str,
        _columns: &[ResolvedColumn],
        params: &[ResolvedParam],
    ) -> Result<String, ScytheError> {
        let func_name = fn_name(&analyzed.name, &self.manifest.naming);
        let mut out = String::new();

        if let Some(ref msg) = analyzed.deprecated {
            let _ = writeln!(out, "#[deprecated(note = \"{}\")]", msg);
        }

        let sql = crate::sql_literal::rust_raw_string_literal(&super::rewrite_pg_placeholders(
            &super::clean_sql_with_optional(&analyzed.sql, &analyzed.optional_params, &analyzed.params),
            |n| format!("@p{n}"),
        ));

        let mut param_parts: Vec<String> =
            vec!["client: &mut tiberius::Client<tokio_util::compat::Compat<tokio::net::TcpStream>>".to_string()];
        for param in params {
            param_parts.push(format!("{}: {}", param.field_name, param.borrowed_type));
        }

        if matches!(analyzed.command, QueryCommand::Batch) {
            let batch_fn_name = format!("{}_batch", func_name);
            if params.len() > 1 {
                let params_struct_name = format!("{}BatchParams", struct_name);
                let _ = writeln!(out, "{}", self.struct_derives());
                let _ = writeln!(out, "pub struct {} {{", params_struct_name);
                for param in params {
                    let _ = writeln!(out, "    pub {}: {},", param.field_name, param.full_type);
                }
                let _ = writeln!(out, "}}");
                let _ = writeln!(out);
                let _ = writeln!(
                    out,
                    "pub async fn {}(client: &mut tiberius::Client<tokio_util::compat::Compat<tokio::net::TcpStream>>, items: &[{}]) -> Result<(), tiberius::error::Error> {{",
                    batch_fn_name, params_struct_name
                );
                let _ = writeln!(out, "    for item in items {{");
                let bind_args: Vec<String> = params
                    .iter()
                    .map(|p| format!("&item.{} as &dyn tiberius::ToSql", p.field_name))
                    .collect();
                let _ = writeln!(
                    out,
                    "        client.execute({}, &[{}]).await?;",
                    sql,
                    bind_args.join(", ")
                );
                let _ = writeln!(out, "    }}");
                let _ = writeln!(out, "    Ok(())");
            } else if params.len() == 1 {
                let _ = writeln!(
                    out,
                    "pub async fn {}(client: &mut tiberius::Client<tokio_util::compat::Compat<tokio::net::TcpStream>>, items: &[{}]) -> Result<(), tiberius::error::Error> {{",
                    batch_fn_name, params[0].full_type
                );
                let _ = writeln!(out, "    for item in items {{");
                let _ = writeln!(out, "        client.execute({}, &[item]).await?;", sql);
                let _ = writeln!(out, "    }}");
                let _ = writeln!(out, "    Ok(())");
            } else {
                let _ = writeln!(
                    out,
                    "pub async fn {}(client: &mut tiberius::Client<tokio_util::compat::Compat<tokio::net::TcpStream>>, count: usize) -> Result<(), tiberius::error::Error> {{",
                    batch_fn_name
                );
                let _ = writeln!(out, "    for _ in 0..count {{");
                let _ = writeln!(out, "        client.execute({}, &[]).await?;", sql);
                let _ = writeln!(out, "    }}");
                let _ = writeln!(out, "    Ok(())");
            }
            let _ = write!(out, "}}");
            return Ok(out);
        }

        let return_type = match &analyzed.command {
            QueryCommand::One => struct_name.to_string(),
            QueryCommand::Opt => format!("Option<{}>", struct_name),
            QueryCommand::Many => format!("Vec<{}>", struct_name),
            QueryCommand::Exec => "()".to_string(),
            QueryCommand::ExecResult | QueryCommand::ExecRows => "u64".to_string(),
            QueryCommand::Batch => unreachable!(),
            QueryCommand::Grouped => {
                unreachable!("Grouped command is routed through generate_grouped_query_fn, not generate_query_fn")
            }
        };

        let _ = writeln!(
            out,
            "pub async fn {}({}) -> Result<{}, tiberius::error::Error> {{",
            func_name,
            param_parts.join(", "),
            return_type
        );

        let param_slice: String = if params.is_empty() {
            "&[]".to_string()
        } else {
            let param_refs: Vec<String> = params
                .iter()
                .map(|p| {
                    let bt = &p.borrowed_type;
                    if bt == "&str" || bt == "Option<&str>" {
                        if bt == "Option<&str>" {
                            format!("&{}.map(|s| s.to_string()) as &dyn tiberius::ToSql", p.field_name)
                        } else {
                            format!("&{}.to_string() as &dyn tiberius::ToSql", p.field_name)
                        }
                    } else if bt.starts_with('&') {
                        format!("{} as &dyn tiberius::ToSql", p.field_name)
                    } else {
                        format!("&{} as &dyn tiberius::ToSql", p.field_name)
                    }
                })
                .collect();
            format!("&[{}]", param_refs.join(", "))
        };

        match &analyzed.command {
            QueryCommand::One => {
                let _ = writeln!(out, "    let stream = client.query({}, {}).await?;", sql, param_slice);
                let _ = writeln!(
                    out,
                    "    let row = stream.into_row().await?.expect(\"expected one row\");"
                );
                let _ = writeln!(out, "    Ok({}::from_row(&row)?)", struct_name);
            }
            QueryCommand::Opt => {
                let _ = writeln!(out, "    let stream = client.query({}, {}).await?;", sql, param_slice);
                let _ = writeln!(out, "    let row = stream.into_row().await?;");
                let _ = writeln!(out, "    row.map(|r| {}::from_row(&r)).transpose()", struct_name);
            }
            QueryCommand::Many => {
                let _ = writeln!(out, "    let stream = client.query({}, {}).await?;", sql, param_slice);
                let _ = writeln!(out, "    let rows = stream.into_first_result().await?;");
                let _ = writeln!(out, "    rows.iter().map({}::from_row).collect()", struct_name);
            }
            QueryCommand::Exec => {
                let _ = writeln!(out, "    client.execute({}, {}).await?;", sql, param_slice);
                let _ = writeln!(out, "    Ok(())");
            }
            QueryCommand::ExecResult | QueryCommand::ExecRows => {
                let _ = writeln!(out, "    let result = client.execute({}, {}).await?;", sql, param_slice);
                let _ = writeln!(out, "    Ok(result.total())");
            }
            QueryCommand::Batch => unreachable!(),
            QueryCommand::Grouped => {
                unreachable!("Grouped command is routed through generate_grouped_query_fn, not generate_query_fn")
            }
        }

        let _ = write!(out, "}}");
        Ok(out)
    }

    fn generate_enum_def(&self, enum_info: &EnumInfo) -> Result<String, ScytheError> {
        let type_name = enum_type_name(&enum_info.sql_name, &self.manifest.naming);
        let mut out = String::with_capacity(512);

        let _ = writeln!(out, "{}", self.enum_derives());
        let _ = writeln!(out, "pub enum {} {{", type_name);
        for value in &enum_info.values {
            let variant = enum_variant_name(value, &self.manifest.naming);
            let _ = writeln!(out, "    {},", variant);
        }
        let _ = writeln!(out, "}}");
        let _ = writeln!(out);

        let _ = writeln!(out, "impl std::fmt::Display for {} {{", type_name);
        let _ = writeln!(
            out,
            "    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {{"
        );
        let _ = writeln!(out, "        match self {{");
        for value in &enum_info.values {
            let variant = enum_variant_name(value, &self.manifest.naming);
            let _ = writeln!(
                out,
                "            {}::{} => write!(f, \"{}\"),",
                type_name, variant, value
            );
        }
        let _ = writeln!(out, "        }}");
        let _ = writeln!(out, "    }}");
        let _ = writeln!(out, "}}");
        let _ = writeln!(out);

        let _ = writeln!(out, "impl std::str::FromStr for {} {{", type_name);
        let _ = writeln!(out, "    type Err = String;");
        let _ = writeln!(out, "    fn from_str(s: &str) -> Result<Self, Self::Err> {{");
        let _ = writeln!(out, "        match s {{");
        for value in &enum_info.values {
            let variant = enum_variant_name(value, &self.manifest.naming);
            let _ = writeln!(out, "            \"{}\" => Ok({}::{}),", value, type_name, variant);
        }
        let _ = writeln!(out, "            _ => Err(format!(\"unknown variant: {{}}\", s)),");
        let _ = writeln!(out, "        }}");
        let _ = writeln!(out, "    }}");
        let _ = write!(out, "}}");

        Ok(out)
    }

    fn generate_grouped_structs(
        &self,
        parent_struct_name: &str,
        child_struct_name: &str,
        parent_columns: &[crate::backend_trait::ResolvedColumn],
        child_columns: &[crate::backend_trait::ResolvedColumn],
        _key_column: &str,
    ) -> Result<String, ScytheError> {
        let mut out = String::new();

        let _ = writeln!(out, "{}", self.struct_derives());
        let _ = writeln!(out, "pub struct {} {{", child_struct_name);
        for col in child_columns {
            let _ = writeln!(out, "    pub {}: {},", col.field_name, col.full_type);
        }
        let _ = writeln!(out, "}}");
        let _ = writeln!(out);
        let _ = writeln!(out, "impl {} {{", child_struct_name);
        let _ = writeln!(
            out,
            "    pub fn from_row(row: &tiberius::Row) -> Result<Self, tiberius::error::Error> {{"
        );
        let _ = writeln!(out, "        Ok(Self {{");
        for col in child_columns {
            let _ = writeln!(out, "            {},", Self::tiberius_field_init(col));
        }
        let _ = writeln!(out, "        }})");
        let _ = writeln!(out, "    }}");
        let _ = writeln!(out, "}}");

        let _ = writeln!(out);

        let _ = writeln!(out, "{}", self.struct_derives());
        let _ = writeln!(out, "pub struct {} {{", parent_struct_name);
        for col in parent_columns {
            let _ = writeln!(out, "    pub {}: {},", col.field_name, col.full_type);
        }
        let _ = writeln!(out, "    pub children: Vec<{}>,", child_struct_name);
        let _ = write!(out, "}}");

        Ok(out)
    }

    fn generate_grouped_query_fn(
        &self,
        request: &crate::backend_trait::GroupedQueryFn<'_>,
    ) -> Result<String, ScytheError> {
        let analyzed = request.analyzed;
        let parent_struct_name = request.parent_struct_name;
        let child_struct_name = request.child_struct_name;
        let parent_columns = request.parent_columns;
        let params = request.params;
        let key_column = request.key_column;

        let func_name = fn_name(&analyzed.name, &self.manifest.naming);
        let key_field = to_snake_case(key_column);
        let mut out = String::new();

        if let Some(ref msg) = analyzed.deprecated {
            let _ = writeln!(out, "#[deprecated(note = \"{msg}\")]");
        }

        let mut param_parts: Vec<String> =
            vec!["client: &mut tiberius::Client<tokio_util::compat::Compat<tokio::net::TcpStream>>".to_string()];
        for param in params {
            param_parts.push(format!("{}: {}", param.field_name, param.borrowed_type));
        }

        let sql = crate::sql_literal::rust_raw_string_literal(&super::rewrite_pg_placeholders(
            &super::clean_sql_with_optional(&analyzed.sql, &analyzed.optional_params, &analyzed.params),
            |n| format!("@p{n}"),
        ));

        let param_slice: String = if params.is_empty() {
            "&[]".to_string()
        } else {
            let refs: Vec<String> = params
                .iter()
                .map(|p| {
                    let bt = &p.borrowed_type;
                    if bt == "&str" || bt == "Option<&str>" {
                        if bt == "Option<&str>" {
                            format!("&{}.map(|s| s.to_string()) as &dyn tiberius::ToSql", p.field_name)
                        } else {
                            format!("&{}.to_string() as &dyn tiberius::ToSql", p.field_name)
                        }
                    } else if bt.starts_with('&') {
                        format!("{} as &dyn tiberius::ToSql", p.field_name)
                    } else {
                        format!("&{} as &dyn tiberius::ToSql", p.field_name)
                    }
                })
                .collect();
            format!("&[{}]", refs.join(", "))
        };

        let key_col_type = parent_columns
            .iter()
            .find(|c| c.name == key_column || c.field_name == key_field)
            .map(|c| c.full_type.as_str())
            .unwrap_or("i64");

        let _ = writeln!(
            out,
            "pub async fn {}({}) -> Result<Vec<{}>, tiberius::error::Error> {{",
            func_name,
            param_parts.join(", "),
            parent_struct_name
        );

        let _ = writeln!(out, "    let stream = client.query({}, {}).await?;", sql, param_slice);
        let _ = writeln!(out, "    let rows = stream.into_first_result().await?;");
        let _ = writeln!(out, "    let mut result: Vec<{}> = Vec::new();", parent_struct_name);
        let _ = writeln!(out, "    for row in &rows {{");

        for col in parent_columns {
            let decode = Self::tiberius_decode_col(col);
            let _ = writeln!(out, "        let {}: {} = {decode};", col.field_name, col.full_type);
        }

        let _ = writeln!(out, "        let key: {key_col_type} = {key_field}.clone();");

        let _ = writeln!(out, "        let child = {}::from_row(row)?;", child_struct_name);

        let _ = writeln!(
            out,
            "        if let Some(parent) = result.iter_mut().rev().find(|p| p.{key_field} == key) {{"
        );
        let _ = writeln!(out, "            parent.children.push(child);");
        let _ = writeln!(out, "        }} else {{");
        let _ = writeln!(out, "            result.push({} {{", parent_struct_name);
        for col in parent_columns {
            let _ = writeln!(out, "                {},", col.field_name);
        }
        let _ = writeln!(out, "                children: vec![child],");
        let _ = writeln!(out, "            }});");
        let _ = writeln!(out, "        }}");
        let _ = writeln!(out, "    }}");
        let _ = writeln!(out, "    Ok(result)");
        let _ = write!(out, "}}");

        Ok(out)
    }

    fn generate_composite_def(&self, composite: &CompositeInfo) -> Result<String, ScytheError> {
        let struct_name = composite_type_name(&composite.sql_name, &self.manifest.naming);
        let mut out = String::new();

        let _ = writeln!(out, "{}", self.struct_derives());
        let _ = writeln!(out, "pub struct {} {{", struct_name);
        for field in &composite.fields {
            let rust_type = resolve_type(&field.neutral_type, &self.manifest, field.nullable)
                .map(|t| t.into_owned())
                .map_err(|e| {
                    ScytheError::new(ErrorCode::InternalError, format!("composite field type error: {}", e))
                })?;
            let _ = writeln!(out, "    pub {}: {},", to_snake_case(&field.name), rust_type);
        }
        let _ = write!(out, "}}");
        Ok(out)
    }
}

#[cfg(test)]
mod tests {
    use scythe_core::analyzer::{AnalyzedColumn, AnalyzedQuery, GroupByConfig};
    use scythe_core::parser::QueryCommand;

    use super::RustTiberiusBackend;
    use crate::backend_trait::CodegenBackend;
    use crate::generate_with_backend;

    fn make_grouped_query() -> AnalyzedQuery {
        let parent_cols = vec![
            AnalyzedColumn {
                name: "id".to_string(),
                neutral_type: "int32".to_string(),
                nullable: false,
                ..Default::default()
            },
            AnalyzedColumn {
                name: "name".to_string(),
                neutral_type: "string".to_string(),
                nullable: false,
                ..Default::default()
            },
            AnalyzedColumn {
                name: "email".to_string(),
                neutral_type: "string".to_string(),
                nullable: false,
                ..Default::default()
            },
        ];
        let child_cols = vec![
            AnalyzedColumn {
                name: "order_id".to_string(),
                neutral_type: "int32".to_string(),
                nullable: false,
                ..Default::default()
            },
            AnalyzedColumn {
                name: "total".to_string(),
                neutral_type: "decimal".to_string(),
                nullable: true,
                ..Default::default()
            },
            AnalyzedColumn {
                name: "order_date".to_string(),
                neutral_type: "datetime".to_string(),
                nullable: false,
                ..Default::default()
            },
        ];
        let all_cols = [parent_cols.clone(), child_cols.clone()].concat();
        AnalyzedQuery::build(|aq| {
            aq.name = "GetUsersWithOrders".to_string();
            aq.command = QueryCommand::Grouped;
            aq.sql = "-- @name GetUsersWithOrders\n-- @returns :grouped\n-- @group_by users.id\n\
                  SELECT u.id, u.name, u.email, o.id AS order_id, o.total, o.created_at AS order_date\n\
                  FROM users u\n\
                  JOIN orders o ON o.user_id = u.id"
                .to_string();
            aq.columns = all_cols;
            aq.params = vec![];
            aq.deprecated = None;
            aq.source_table = None;
            aq.composites = vec![];
            aq.enums = vec![];
            aq.optional_params = vec![];
            aq.group_by = Some(GroupByConfig {
                table: "users".to_string(),
                key_column: "id".to_string(),
                parent_columns: parent_cols,
                child_columns: child_cols,
            });
            aq.custom = vec![];
        })
    }

    #[test]
    fn test_grouped_tiberius_structs() {
        let backend = RustTiberiusBackend::new("mssql").unwrap();
        let query = make_grouped_query();
        let result = generate_with_backend(&query, &backend).unwrap();

        let row_struct = result.row_struct.as_deref().unwrap();

        assert!(
            row_struct.contains("pub struct GetUsersWithOrdersChildRow"),
            "missing child struct; got:\n{row_struct}"
        );
        assert!(
            row_struct.contains("pub order_id: i32"),
            "child struct missing order_id; got:\n{row_struct}"
        );
        assert!(
            row_struct.contains("pub struct GetUsersWithOrdersRow"),
            "missing parent struct; got:\n{row_struct}"
        );
        assert!(
            row_struct.contains("pub id: i32"),
            "parent struct missing id; got:\n{row_struct}"
        );
        assert!(
            row_struct.contains("pub name: String"),
            "parent struct missing name; got:\n{row_struct}"
        );
        assert!(
            row_struct.contains("pub children: Vec<GetUsersWithOrdersChildRow>"),
            "parent struct missing children field; got:\n{row_struct}"
        );
        let child_pos = row_struct.find("GetUsersWithOrdersChildRow").unwrap();
        let parent_pos = row_struct.find("pub struct GetUsersWithOrdersRow").unwrap();
        assert!(child_pos < parent_pos, "child struct must appear before parent struct");

        assert!(
            row_struct.contains("fn from_row(row: &tiberius::Row)"),
            "child struct should include from_row; got:\n{row_struct}"
        );
        assert!(result.model_struct.is_none(), "grouped must not produce a model_struct");
    }

    #[test]
    fn test_grouped_tiberius_query_fn() {
        let backend = RustTiberiusBackend::new("mssql").unwrap();
        let query = make_grouped_query();
        let result = generate_with_backend(&query, &backend).unwrap();

        let query_fn = result.query_fn.as_deref().unwrap();

        assert!(
            query_fn.contains("pub async fn get_users_with_orders("),
            "missing fn; got:\n{query_fn}"
        );
        assert!(
            query_fn.contains("-> Result<Vec<GetUsersWithOrdersRow>, tiberius::error::Error>"),
            "wrong return type; got:\n{query_fn}"
        );
        assert!(
            query_fn.contains("into_first_result()"),
            "fn must use into_first_result; got:\n{query_fn}"
        );
        assert!(
            query_fn.contains("GetUsersWithOrdersChildRow::from_row(row)?"),
            "fn must call child from_row; got:\n{query_fn}"
        );
        assert!(
            query_fn.contains("children: vec![child]"),
            "fn must initialize children vec; got:\n{query_fn}"
        );
        assert!(
            query_fn.contains("parent.children.push(child)"),
            "fn must fold child into existing parent; got:\n{query_fn}"
        );
        assert!(
            query_fn.contains("Ok(result)"),
            "fn must return result; got:\n{query_fn}"
        );
    }

    /// Regression test for a release-blocking bug: `[sql.gen.rust] serde =
    /// true` / `derive = [...]` are documented as target-independent options
    /// under the legacy `[sql.gen.rust]` table, and the CLI's
    /// `resolve_gen_targets` inserts them into the options map regardless of
    /// which `target` the user picked (`sqlx`, `tokio-postgres`, `tiberius`,
    /// or `sibyl`). rust-tiberius's row/enum/composite structs are all plain
    /// Rust types with no macro-derived driver coupling (unlike sqlx's
    /// `sqlx::FromRow`/`sqlx::Type`), so there is no technical reason serde
    /// support should be limited to rust-tokio-postgres; before this,
    /// rust-tiberius had no `apply_options` override at all and inherited
    /// the `CodegenBackend` trait default that rejects every key, so this
    /// config hard-errored with "unknown option 'serde'".
    #[test]
    fn serde_and_derive_options_apply_together() {
        let mut backend = RustTiberiusBackend::new("mssql").unwrap();
        backend
            .apply_options(&std::collections::HashMap::from([
                ("serde".to_string(), "true".to_string()),
                ("derive".to_string(), "PartialEq, Eq".to_string()),
            ]))
            .unwrap();
        assert!(backend.serde);
        assert_eq!(backend.extra_derives, vec!["PartialEq".to_string(), "Eq".to_string()]);
    }

    /// An unrecognized value must be reported, not silently treated as
    /// leaving `serde` disabled.
    #[test]
    fn serde_option_rejects_invalid_value() {
        let mut backend = RustTiberiusBackend::new("mssql").unwrap();
        let result = backend.apply_options(&std::collections::HashMap::from([(
            "serde".to_string(),
            "maybe".to_string(),
        )]));
        assert!(result.is_err(), "expected 'maybe' to be rejected");
    }

    /// A key that is neither `serde` nor `derive` must still be rejected --
    /// rust-tiberius takes exactly these two options, nothing else.
    #[test]
    fn apply_options_rejects_unknown_key() {
        let mut backend = RustTiberiusBackend::new("mssql").unwrap();
        let err = backend
            .apply_options(&std::collections::HashMap::from([(
                "structs_only".to_string(),
                "true".to_string(),
            )]))
            .expect_err("structs_only is not a rust-tiberius option");
        assert_eq!(err.code, scythe_core::errors::ErrorCode::InvalidConfig);
        assert!(err.message.contains("structs_only"), "{}", err.message);
    }

    /// The regression itself: applying `serde`/`derive` must not just avoid
    /// erroring, the emitted row struct must actually carry the derives.
    #[test]
    fn serde_and_derive_options_generate_row_struct_with_serde_derive() {
        let mut backend = RustTiberiusBackend::new("mssql").unwrap();
        backend
            .apply_options(&std::collections::HashMap::from([
                ("serde".to_string(), "true".to_string()),
                ("derive".to_string(), "PartialEq".to_string()),
            ]))
            .unwrap();

        let query = AnalyzedQuery::build(|aq| {
            aq.name = "GetUser".to_string();
            aq.command = QueryCommand::Opt;
            aq.sql = "SELECT id, name FROM users".to_string();
            aq.columns = vec![
                AnalyzedColumn {
                    name: "id".to_string(),
                    neutral_type: "int32".to_string(),
                    nullable: false,
                    ..Default::default()
                },
                AnalyzedColumn {
                    name: "name".to_string(),
                    neutral_type: "string".to_string(),
                    nullable: false,
                    ..Default::default()
                },
            ];
        });

        let result = generate_with_backend(&query, &backend).unwrap();
        let row_struct = result.row_struct.as_deref().unwrap();

        assert!(
            row_struct.contains("#[derive(Debug, Clone, serde::Serialize, serde::Deserialize, PartialEq)]"),
            "row struct must carry the base derives plus serde and the extra derive; got:\n{row_struct}"
        );
    }
}