Merge #8873

8873: Implement import-granularity guessing  r=matklad a=Veykril

This renames our `MergeBehavior` to `ImportGranularity` as rustfmt has it as the purpose of them are basically the same. `ImportGranularity::Preserve` currently has no specific purpose for us as we don't have an organize imports assist yet, so it currently acts the same as `ImportGranularity::Item`.

We now try to guess the import style on a per file basis and fall back to the user granularity setting if the file has no specific style yet or where it is ambiguous. This can be turned off by setting `import.enforceGranularity` to `true`.

Closes https://github.com/rust-analyzer/rust-analyzer/issues/8870

Co-authored-by: Lukas Tobias Wirth <lukastw97@gmail.com>

crates/rust-analyzer/src/config.rs

@@ -12,8 +12,7 @@ use std::{ffi::OsString, iter, path::PathBuf};
 use flycheck::FlycheckConfig;
 use ide::{AssistConfig, CompletionConfig, DiagnosticsConfig, HoverConfig, InlayHintsConfig};
 use ide_db::helpers::{
-    insert_use::{InsertUseConfig, PrefixKind},
-    merge_imports::MergeBehavior,
+    insert_use::{ImportGranularity, InsertUseConfig, PrefixKind},
     SnippetCap,
 };
 use lsp_types::{ClientCapabilities, MarkupKind};
@@ -35,15 +34,18 @@ use crate::{
 // be specified directly in `package.json`.
 config_data! {
     struct ConfigData {
-        /// The strategy to use when inserting new imports or merging imports.
+        /// How imports should be grouped into use statements.
+        assist_importGranularity |
         assist_importMergeBehavior |
-        assist_importMergeBehaviour: MergeBehaviorDef  = "\"crate\"",
+        assist_importMergeBehaviour: ImportGranularityDef  = "\"crate\"",
+        /// Whether to enforce the import granularity setting for all files. If set to false rust-analyzer will try to keep import styles consistent per file.
+        assist_importEnforceGranularity: bool              = "false",
         /// The path structure for newly inserted paths to use.
-        assist_importPrefix: ImportPrefixDef           = "\"plain\"",
+        assist_importPrefix: ImportPrefixDef               = "\"plain\"",
         /// Group inserted imports by the [following order](https://rust-analyzer.github.io/manual.html#auto-import). Groups are separated by newlines.
-        assist_importGroup: bool                       = "true",
+        assist_importGroup: bool                           = "true",
         /// Show function name and docs in parameter hints.
-        callInfo_full: bool = "true",
+        callInfo_full: bool                                = "true",
 
         /// Automatically refresh project info via `cargo metadata` on
         /// `Cargo.toml` changes.
@@ -624,11 +626,13 @@ impl Config {
     }
     fn insert_use_config(&self) -> InsertUseConfig {
         InsertUseConfig {
-            merge: match self.data.assist_importMergeBehavior {
-                MergeBehaviorDef::None => None,
-                MergeBehaviorDef::Crate => Some(MergeBehavior::Crate),
-                MergeBehaviorDef::Module => Some(MergeBehavior::Module),
+            granularity: match self.data.assist_importGranularity {
+                ImportGranularityDef::Preserve => ImportGranularity::Preserve,
+                ImportGranularityDef::Item => ImportGranularity::Item,
+                ImportGranularityDef::Crate => ImportGranularity::Crate,
+                ImportGranularityDef::Module => ImportGranularity::Module,
             },
+            enforce_granularity: self.data.assist_importEnforceGranularity,
             prefix_kind: match self.data.assist_importPrefix {
                 ImportPrefixDef::Plain => PrefixKind::Plain,
                 ImportPrefixDef::ByCrate => PrefixKind::ByCrate,
@@ -748,8 +752,10 @@ enum ManifestOrProjectJson {
 
 #[derive(Deserialize, Debug, Clone)]
 #[serde(rename_all = "snake_case")]
-enum MergeBehaviorDef {
-    None,
+enum ImportGranularityDef {
+    Preserve,
+    #[serde(alias = "none")]
+    Item,
     #[serde(alias = "full")]
     Crate,
     #[serde(alias = "last")]
@@ -782,7 +788,7 @@ macro_rules! _config_data {
     (struct $name:ident {
         $(
             $(#[doc=$doc:literal])*
-            $field:ident $(| $alias:ident)?: $ty:ty = $default:expr,
+            $field:ident $(| $alias:ident)*: $ty:ty = $default:expr,
         )*
     }) => {
         #[allow(non_snake_case)]
@@ -794,7 +800,7 @@ macro_rules! _config_data {
                     $field: get_field(
                         &mut json,
                         stringify!($field),
-                        None$(.or(Some(stringify!($alias))))?,
+                        None$(.or(Some(stringify!($alias))))*,
                         $default,
                     ),
                 )*}
@@ -931,6 +937,16 @@ fn field_props(field: &str, ty: &str, doc: &[&str], default: &str) -> serde_json
                 "Merge imports from the same module into a single `use` statement."
             ],
         },
+        "ImportGranularityDef" => set! {
+            "type": "string",
+            "enum": ["preserve", "crate", "module", "item"],
+            "enumDescriptions": [
+                "Do not change the granularity of any imports and preserve the original structure written by the developer.",
+                "Merge imports from the same crate into a single use statement. Conversely, imports from different crates are split into separate statements.",
+                "Merge imports from the same module into a single use statement. Conversely, imports from different modules are split into separate statements.",
+                "Flatten imports so that each has its own use statement."
+            ],
+        },
         "ImportPrefixDef" => set! {
             "type": "string",
             "enum": [