Merge pull request #543 from MichaReiser/input-builder

Introduce `Input::builder` API

components/salsa-macro-rules/src/lib.rs

@@ -15,6 +15,7 @@
 mod macro_if;
 mod maybe_backdate;
 mod maybe_clone;
+mod maybe_default;
 mod setup_accumulator_impl;
 mod setup_input_struct;
 mod setup_interned_struct;

components/salsa-macro-rules/src/maybe_backdate.rs

@@ -2,7 +2,7 @@
 #[macro_export]
 macro_rules! maybe_backdate {
     (
-        ($maybe_clone:ident, no_backdate),
+        ($maybe_clone:ident, no_backdate, $maybe_default:ident),
         $field_ty:ty,
         $old_field_place:expr,
         $new_field_place:expr,
@@ -20,7 +20,7 @@ macro_rules! maybe_backdate {
     };
 
     (
-        ($maybe_clone:ident, backdate),
+        ($maybe_clone:ident, backdate, $maybe_default:ident),
         $field_ty:ty,
         $old_field_place:expr,
         $new_field_place:expr,

components/salsa-macro-rules/src/maybe_clone.rs

@@ -4,15 +4,15 @@
 #[macro_export]
 macro_rules! maybe_clone {
     (
-        (no_clone, $maybe_backdate:ident),
+        (no_clone, $maybe_backdate:ident, $maybe_default:ident),
         $field_ty:ty,
         $field_ref_expr:expr,
     ) => {
         $field_ref_expr
     };
 
     (
-        (clone, $maybe_backdate:ident),
+        (clone, $maybe_backdate:ident, $maybe_default:ident),
         $field_ty:ty,
         $field_ref_expr:expr,
     ) => {
@@ -23,15 +23,15 @@ macro_rules! maybe_clone {
 #[macro_export]
 macro_rules! maybe_cloned_ty {
     (
-        (no_clone, $maybe_backdate:ident),
+        (no_clone, $maybe_backdate:ident, $maybe_default:ident),
         $db_lt:lifetime,
         $field_ty:ty
     ) => {
         & $db_lt $field_ty
     };
 
     (
-        (clone, $maybe_backdate:ident),
+        (clone, $maybe_backdate:ident, $maybe_default:ident),
         $db_lt:lifetime,
         $field_ty:ty
     ) => {

components/salsa-macro-rules/src/maybe_default.rs

@@ -0,0 +1,32 @@
+/// Generate either `field_ref_expr` or `field_ty::default`
+///
+/// Used when generating an input's builder.
+#[macro_export]
+macro_rules! maybe_default {
+    (
+        ($maybe_clone:ident, $maybe_backdate:ident, default),
+        $field_ty:ty,
+        $field_ref_expr:expr,
+    ) => {
+        <$field_ty>::default()
+    };
+
+    (
+        ($maybe_clone:ident, $maybe_backdate:ident, required),
+        $field_ty:ty,
+        $field_ref_expr:expr,
+    ) => {
+        $field_ref_expr
+    };
+}
+
+#[macro_export]
+macro_rules! maybe_default_tt {
+    (($maybe_clone:ident, $maybe_backdate:ident, default) => $($t:tt)*) => {
+        $($t)*
+    };
+
+    (($maybe_clone:ident, $maybe_backdate:ident, required) => $($t:tt)*) => {
+
+    };
+}

components/salsa-macro-rules/src/setup_input_struct.rs

@@ -32,6 +32,12 @@ macro_rules! setup_input_struct {
         // Indices for each field from 0..N -- must be unsuffixed (e.g., `0`, `1`).
         field_indices: [$($field_index:tt),*],
 
+        // Fields that are required (have no default value). Each item is the fields name and type.
+        required_fields: [$($required_field_id:ident $required_field_ty:ty),*],
+
+        // Names for the field durability methods on the builder (typically `foo_durability`)
+        field_durability_ids: [$($field_durability_id:ident),*],
+
         // Number of fields
         num_fields: $N:literal,
 
@@ -48,6 +54,7 @@ macro_rules! setup_input_struct {
             $zalsa:ident,
             $zalsa_struct:ident,
             $Configuration:ident,
+            $Builder:ident,
             $CACHE:ident,
             $Db:ident,
         ]
@@ -123,14 +130,18 @@ macro_rules! setup_input_struct {
             }
 
             impl $Struct {
-                pub fn $new_fn<$Db>(db: &$Db, $($field_id: $field_ty),*) -> Self
+                #[inline]
+                pub fn $new_fn<$Db>(db: &$Db, $($required_field_id: $required_field_ty),*) -> Self
                 where
                     // FIXME(rust-lang/rust#65991): The `db` argument *should* have the type `dyn Database`
                     $Db: ?Sized + salsa::Database,
                 {
-                    let current_revision = $zalsa::current_revision(db);
-                    let stamps = $zalsa::Array::new([$zalsa::stamp(current_revision, Default::default()); $N]);
-                    $Configuration::ingredient(db.as_dyn_database()).new_input(($($field_id,)*), stamps)
+                    Self::builder($($required_field_id,)*).new(db)
+                }
+
+                pub fn builder($($required_field_id: $required_field_ty),*) -> <Self as $zalsa_struct::HasBuilder>::Builder
+                {
+                    builder::new_builder($($zalsa::maybe_default!($field_option, $field_ty, $field_id,)),*)
                 }
 
                 $(
@@ -206,6 +217,90 @@ macro_rules! setup_input_struct {
                     })
                 }
             }
+
+            impl $zalsa_struct::HasBuilder for $Struct {
+                type Builder = builder::$Builder;
+            }
+
+            // Implement `new` here instead of inside the builder module
+            // because $Configuration can't be named in `builder`.
+            impl builder::$Builder {
+                /// Creates the new input with the set values.
+                #[must_use]
+                pub fn new<$Db>(self, db: &$Db) -> $Struct
+                where
+                    // FIXME(rust-lang/rust#65991): The `db` argument *should* have the type `dyn Database`
+                    $Db: ?Sized + salsa::Database
+                {
+                    let current_revision = $zalsa::current_revision(db);
+                    let ingredient = $Configuration::ingredient(db.as_dyn_database());
+                    let (fields, stamps) = builder::builder_into_inner(self, current_revision);
+                    ingredient.new_input(fields, stamps)
+                }
+            }
+
+            mod builder {
+                use super::*;
+
+                use salsa::plumbing as $zalsa;
+                use $zalsa::input as $zalsa_struct;
+
+                // These are standalone functions instead of methods on `Builder` to prevent
+                // that the enclosing module can call them.
+                pub(super) fn new_builder($($field_id: $field_ty),*) -> $Builder {
+                    $Builder {
+                        fields: ($($field_id,)*),
+                        durabilities: [salsa::Durability::default(); $N],
+                    }
+                }
+
+                pub(super) fn builder_into_inner(builder: $Builder, revision: $zalsa::Revision) -> (($($field_ty,)*), $zalsa::Array<$zalsa::Stamp, $N>) {
+                    let stamps = $zalsa::Array::new([
+                        $($zalsa::stamp(revision, builder.durabilities[$field_index])),*
+                    ]);
+
+                    (builder.fields, stamps)
+                }
+
+                #[must_use]
+                pub struct $Builder {
+                    /// The field values.
+                    fields: ($($field_ty,)*),
+
+                    /// The durabilities per field.
+                    durabilities: [salsa::Durability; $N],
+                }
+
+                impl $Builder {
+                    /// Sets the durability of all fields.
+                    ///
+                    /// Overrides any previously set durabilities.
+                    pub fn durability(mut self, durability: salsa::Durability) -> Self {
+                        self.durabilities = [durability; $N];
+                        self
+                    }
+
+                    $($zalsa::maybe_default_tt! { $field_option =>
+                        /// Sets the value of the field `$field_id`.
+                        #[must_use]
+                        pub fn $field_id(mut self, value: $field_ty) -> Self
+                        {
+                            self.fields.$field_index = value;
+                            self
+                        }
+                    })*
+
+                    $(
+                        /// Sets the durability for the field `$field_id`.
+                        #[must_use]
+                        pub fn $field_durability_id(mut self, durability: salsa::Durability) -> Self
+                        {
+                            self.durabilities[$field_index] = durability;
+                            self
+                        }
+                    )*
+                }
+            }
         };
     };
 }

components/salsa-macros/src/input.rs

@@ -62,6 +62,8 @@ impl SalsaStructAllowedOptions for InputStruct {
     const ALLOW_ID: bool = false;
 
     const HAS_LIFETIME: bool = false;
+
+    const ALLOW_DEFAULT: bool = true;
 }
 
 struct Macro {
@@ -85,14 +87,17 @@ impl Macro {
         let field_vis = salsa_struct.field_vis();
         let field_getter_ids = salsa_struct.field_getter_ids();
         let field_setter_ids = salsa_struct.field_setter_ids();
+        let required_fields = salsa_struct.required_fields();
         let field_options = salsa_struct.field_options();
         let field_tys = salsa_struct.field_tys();
+        let field_durability_ids = salsa_struct.field_durability_ids();
         let is_singleton = self.args.singleton.is_some();
         let generate_debug_impl = salsa_struct.generate_debug_impl();
 
         let zalsa = self.hygiene.ident("zalsa");
         let zalsa_struct = self.hygiene.ident("zalsa_struct");
         let Configuration = self.hygiene.ident("Configuration");
+        let Builder = self.hygiene.ident("Builder");
         let CACHE = self.hygiene.ident("CACHE");
         let Db = self.hygiene.ident("Db");
 
@@ -110,13 +115,16 @@ impl Macro {
                     field_setters: [#(#field_vis #field_setter_ids),*],
                     field_tys: [#(#field_tys),*],
                     field_indices: [#(#field_indices),*],
+                    required_fields: [#(#required_fields),*],
+                    field_durability_ids: [#(#field_durability_ids),*],
                     num_fields: #num_fields,
                     is_singleton: #is_singleton,
                     generate_debug_impl: #generate_debug_impl,
                     unused_names: [
                         #zalsa,
                         #zalsa_struct,
                         #Configuration,
+                        #Builder,
                         #CACHE,
                         #Db,
                     ]

components/salsa-macros/src/interned.rs

@@ -63,6 +63,8 @@ impl SalsaStructAllowedOptions for InternedStruct {
     const ALLOW_ID: bool = false;
 
     const HAS_LIFETIME: bool = true;
+
+    const ALLOW_DEFAULT: bool = false;
 }
 
 struct Macro {