feat(diagnostics): add new config to fill default expression

Signed-off-by: Benjamin Coenen <5719034+bnjjj@users.noreply.github.com>

crates/ide/src/lib.rs

@@ -118,7 +118,7 @@ pub use ide_db::{
     symbol_index::Query,
     RootDatabase, SymbolKind,
 };
-pub use ide_diagnostics::{Diagnostic, DiagnosticsConfig, Severity};
+pub use ide_diagnostics::{Diagnostic, DiagnosticsConfig, ExprFillDefaultMode, Severity};
 pub use ide_ssr::SsrError;
 pub use syntax::{TextRange, TextSize};
 pub use text_edit::{Indel, TextEdit};

crates/ide_diagnostics/src/handlers/missing_fields.rs

@@ -64,15 +64,18 @@ fn fixes(ctx: &DiagnosticsContext<'_>, d: &hir::MissingFields) -> Option<Vec<Ass
     });
     let missing_fields = ctx.sema.record_literal_missing_fields(&field_list_parent);
 
-    let generate_default_expr = |ty: &Type| {
-        let krate = ctx.sema.to_module_def(d.file.original_file(ctx.sema.db))?.krate();
-        let default_trait = FamousDefs(&ctx.sema, Some(krate)).core_default_Default();
+    let generate_fill_expr = |ty: &Type| match ctx.config.expr_fill_default {
+        crate::ExprFillDefaultMode::Todo => Some(make::ext::expr_todo()),
+        crate::ExprFillDefaultMode::DefaultImpl => {
+            let krate = ctx.sema.to_module_def(d.file.original_file(ctx.sema.db))?.krate();
+            let default_trait = FamousDefs(&ctx.sema, Some(krate)).core_default_Default();
 
-        match default_trait {
-            Some(default_trait) if ty.impls_trait(ctx.sema.db, default_trait, &[]) => {
-                Some(make::ext::expr_default())
+            match default_trait {
+                Some(default_trait) if ty.impls_trait(ctx.sema.db, default_trait, &[]) => {
+                    Some(make::ext::expr_default())
+                }
+                _ => Some(make::ext::expr_todo()),
             }
-            _ => Some(make::ext::expr_todo()),
         }
     };
 
@@ -83,10 +86,10 @@ fn fixes(ctx: &DiagnosticsContext<'_>, d: &hir::MissingFields) -> Option<Vec<Ass
             if ty.could_unify_with(ctx.sema.db, &candidate_ty) {
                 None
             } else {
-                generate_default_expr(ty)
+                generate_fill_expr(ty)
             }
         } else {
-            generate_default_expr(ty)
+            generate_fill_expr(ty)
         };
         let field =
             make::record_expr_field(make::name_ref(&f.name(ctx.sema.db).to_smol_str()), field_expr)

crates/ide_diagnostics/src/lib.rs

@@ -129,10 +129,22 @@ pub enum Severity {
     WeakWarning,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ExprFillDefaultMode {
+    Todo,
+    DefaultImpl,
+}
+impl Default for ExprFillDefaultMode {
+    fn default() -> Self {
+        Self::Todo
+    }
+}
+
 #[derive(Default, Debug, Clone)]
 pub struct DiagnosticsConfig {
     pub disable_experimental: bool,
     pub disabled: FxHashSet<String>,
+    pub expr_fill_default: ExprFillDefaultMode,
 }
 
 struct DiagnosticsContext<'a> {

crates/rust-analyzer/src/config.rs

@@ -11,8 +11,8 @@ use std::{ffi::OsString, iter, path::PathBuf};
 
 use flycheck::FlycheckConfig;
 use ide::{
-    AssistConfig, CompletionConfig, DiagnosticsConfig, HighlightRelatedConfig, HoverConfig,
-    HoverDocFormat, InlayHintsConfig, JoinLinesConfig, Snippet, SnippetScope,
+    AssistConfig, CompletionConfig, DiagnosticsConfig, ExprFillDefaultMode, HighlightRelatedConfig,
+    HoverConfig, HoverDocFormat, InlayHintsConfig, JoinLinesConfig, Snippet, SnippetScope,
 };
 use ide_db::helpers::{
     insert_use::{ImportGranularity, InsertUseConfig, PrefixKind},
@@ -45,6 +45,8 @@ use crate::{
 // parsing the old name.
 config_data! {
     struct ConfigData {
+        /// How assists will fill missing elements in an expression.
+        assist_exprFillDefault: ExprFillDefaultDef              = "\"todo\"",
         /// How imports should be grouped into use statements.
         assist_importGranularity |
         assist_importMergeBehavior |
@@ -694,6 +696,10 @@ impl Config {
         DiagnosticsConfig {
             disable_experimental: !self.data.diagnostics_enableExperimental,
             disabled: self.data.diagnostics_disabled.clone(),
+            expr_fill_default: match self.data.assist_exprFillDefault {
+                ExprFillDefaultDef::Todo => ExprFillDefaultMode::Todo,
+                ExprFillDefaultDef::DefaultImpl => ExprFillDefaultMode::DefaultImpl,
+            },
         }
     }
     pub fn diagnostics_map(&self) -> DiagnosticsMapConfig {
@@ -1059,6 +1065,15 @@ enum ManifestOrProjectJson {
     ProjectJson(ProjectJsonData),
 }
 
+#[derive(Deserialize, Debug, Clone)]
+#[serde(rename_all = "snake_case")]
+pub enum ExprFillDefaultDef {
+    #[serde(alias = "todo")]
+    Todo,
+    #[serde(alias = "defaultImpl")]
+    DefaultImpl,
+}
+
 #[derive(Deserialize, Debug, Clone)]
 #[serde(rename_all = "snake_case")]
 enum ImportGranularityDef {
@@ -1253,6 +1268,14 @@ fn field_props(field: &str, ty: &str, doc: &[&str], default: &str) -> serde_json
                 "Merge imports from the same module into a single `use` statement."
             ],
         },
+        "ExprFillDefaultDef" => set! {
+            "type": "string",
+            "enum": ["todo", "defaultImpl"],
+            "enumDescriptions": [
+                "Fill missing elements with 'todo' macro",
+                "Fill missing elements with Default::default()"
+            ],
+        },
         "ImportGranularityDef" => set! {
             "type": "string",
             "enum": ["preserve", "crate", "module", "item"],

docs/user/generated_config.adoc

@@ -1,3 +1,8 @@
+[[rust-analyzer.assist.exprFillDefault]]rust-analyzer.assist.exprFillDefault (default: `"todo"`)::
++
+--
+How assists will fill missing elements in an expression.
+--
 [[rust-analyzer.assist.importGranularity]]rust-analyzer.assist.importGranularity (default: `"crate"`)::
 +
 --

editors/code/package.json

@@ -378,6 +378,19 @@
                     "markdownDescription": "Optional settings passed to the debug engine. Example: `{ \"lldb\": { \"terminal\":\"external\"} }`"
                 },
                 "$generated-start": {},
+                "rust-analyzer.assist.exprFillDefault": {
+                    "markdownDescription": "How assists will fill missing elements in an expression.",
+                    "default": "todo",
+                    "type": "string",
+                    "enum": [
+                        "todo",
+                        "defaultImpl"
+                    ],
+                    "enumDescriptions": [
+                        "Fill missing elements with 'todo' macro",
+                        "Fill missing elements with Default::default()"
+                    ]
+                },
                 "rust-analyzer.assist.importGranularity": {
                     "markdownDescription": "How imports should be grouped into use statements.",
                     "default": "crate",