Merge #3549

3549: Implement env! macro r=matklad a=edwin0cheng

This PR implements `env!` macro by adding following things:

1. Added `additional_outdirs` settings in vscode. (naming to be bikeshed)
2. Added `ExternSourceId` which is a wrapping for SourceRootId but only used in extern sources. It is because `OUT_DIR` is not belonged to any crate and we have to access it behind an `AstDatabase`.
3. This PR does not implement the `OUT_DIR` parsing from `cargo check`. I don't have general design about this,  @kiljacken could we reuse some cargo watch code for that ?

~~Block on [#3536]~~

PS: After this PR , we (kind of) completed the `include!(concat!(env!('OUT_DIR'),  "foo.rs")` macro call combo. [Exodia Obliterate!](https://www.youtube.com/watch?v=RfqNH3FoGi0)

Co-authored-by: Edwin Cheng <[email protected]>

3 files changed, 7 insertions, 0 deletions

diff --git a/editors/code/package.json b/editors/code/package.json
index 512885454..1fe8e9f8a 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -224,6 +224,11 @@
                     "default": true,
                     "description": "Whether to ask for permission before downloading any files from the Internet"
                 },
+                "rust-analyzer.additionalOutDirs": {
+                    "type": "object",
+                    "default": {},
+                    "markdownDescription": "Fine grained controls for OUT_DIR `env!(\"OUT_DIR\")` variable. e.g. `{\"foo\":\"/path/to/foo\"}`, "
+                },
                 "rust-analyzer.serverPath": {
                     "type": [
                         "null",
diff --git a/editors/code/src/client.ts b/editors/code/src/client.ts
index 540f7c9ea..6ce3b9235 100644
--- a/editors/code/src/client.ts
+++ b/editors/code/src/client.ts
@@ -37,6 +37,7 @@ export async function createClient(config: Config, serverPath: string): Promise<
             excludeGlobs: config.excludeGlobs,
             useClientWatching: config.useClientWatching,
             featureFlags: config.featureFlags,
+            additionalOutDirs: config.additionalOutDirs,
             withSysroot: config.withSysroot,
             cargoFeatures: config.cargoFeatures,
             rustfmtArgs: config.rustfmtArgs,
diff --git a/editors/code/src/config.ts b/editors/code/src/config.ts
index b72206d3c..3ade7e900 100644
--- a/editors/code/src/config.ts
+++ b/editors/code/src/config.ts
@@ -154,6 +154,7 @@ export class Config {
     get excludeGlobs() { return this.cfg.get("excludeGlobs") as string[]; }
     get useClientWatching() { return this.cfg.get("useClientWatching") as boolean; }
     get featureFlags() { return this.cfg.get("featureFlags") as Record<string, boolean>; }
+    get additionalOutDirs() { return this.cfg.get("additionalOutDirs") as Record<string, string>; }
     get rustfmtArgs() { return this.cfg.get("rustfmtArgs") as string[]; }
 
     get cargoWatchOptions(): CargoWatchOptions {