Allow export map entries to remap back to input files for a program (#47925)

* Allow export map entries to remap back to input files for a program

* Fix file casing issues on windows

* Implement abiguity error, doesnt quite work

* Refine selection logic in error case to use getCommonSourceDirectory, add more tests

tests/cases/compiler/nodeNextPackageImportMapRootDir.ts

@@ -0,0 +1,20 @@
+// @module: nodenext
+// @outDir: ./dist
+// @rootDir: tests/cases/compiler
+// @filename: package.json
+{
+  "name": "@this/package",
+  "type": "module",
+  "exports": {
+    ".": "./dist/index.js"
+  },
+  "imports": {
+    "#dep": "./dist/index.js"
+  }
+}
+// @filename: index.ts
+import * as me from "#dep";
+
+me.thing();
+
+export function thing(): void {}

tests/cases/compiler/nodeNextPackageSelfNameWithOutDir.ts

@@ -0,0 +1,16 @@
+// @module: nodenext
+// @outDir: ./dist
+// @filename: package.json
+{
+  "name": "@this/package",
+  "type": "module",
+  "exports": {
+    ".": "./dist/index.js"
+  }
+}
+// @filename: index.ts
+import * as me from "@this/package";
+
+me.thing();
+
+export function thing(): void {}

tests/cases/compiler/nodeNextPackageSelfNameWithOutDirDeclDir.ts

@@ -0,0 +1,21 @@
+// @module: nodenext
+// @outDir: ./dist
+// @declarationDir: ./types
+// @declaration: true
+// @filename: package.json
+{
+  "name": "@this/package",
+  "type": "module",
+  "exports": {
+    ".": {
+      "default": "./dist/index.js",
+      "types": "./types/index.d.ts"
+    }
+  }
+}
+// @filename: index.ts
+import * as me from "@this/package";
+
+me.thing();
+
+export function thing(): void {}

tests/cases/compiler/nodeNextPackageSelfNameWithOutDirDeclDirComposite.ts

@@ -0,0 +1,26 @@
+// @filename: tsconfig.json
+{
+  "compilerOptions": {
+    "module": "nodenext",
+    "outDir": "./dist",
+    "declarationDir": "./types",
+    "composite": true
+  }
+}
+// @filename: package.json
+{
+  "name": "@this/package",
+  "type": "module",
+  "exports": {
+    ".": {
+      "default": "./dist/index.js",
+      "types": "./types/index.d.ts"
+    }
+  }
+}
+// @filename: index.ts
+import * as me from "@this/package";
+
+me.thing();
+
+export function thing(): void {}

tests/cases/compiler/nodeNextPackageSelfNameWithOutDirDeclDirCompositeNestedDirs.ts

@@ -0,0 +1,37 @@
+// @noImplicitReferences: true
+// @filename: tsconfig.json
+{
+  "compilerOptions": {
+    "module": "nodenext",
+    "outDir": "./dist",
+    "declarationDir": "./types",
+    "composite": true
+  }
+}
+// @filename: package.json
+{
+  "name": "@this/package",
+  "type": "module",
+  "exports": {
+    ".": {
+      "default": "./dist/index.js",
+      "types": "./types/index.d.ts"
+    }
+  }
+}
+// @filename: index.ts
+export {srcthing as thing} from "./src/thing.js";
+// @filename: src/thing.ts
+// The following import should cause `index.ts`
+// to be included in the build, which will,
+// in turn, cause the common src directory to not be `src`
+// (the harness is wierd here in that noImplicitReferences makes only
+// this file get loaded as an entrypoint and emitted, while on the
+// real command-line we'll crawl the imports for that set - a limitation
+// of the harness, I suppose)
+import * as me from "@this/package";
+
+me.thing();
+
+export function srcthing(): void {}
+

tests/cases/compiler/nodeNextPackageSelfNameWithOutDirDeclDirNestedDirs.ts

@@ -0,0 +1,37 @@
+// @noImplicitReferences: true
+// @filename: tsconfig.json
+{
+  "compilerOptions": {
+    "module": "nodenext",
+    "outDir": "./dist",
+    "declarationDir": "./types",
+    "declaration": true
+  }
+}
+// @filename: package.json
+{
+  "name": "@this/package",
+  "type": "module",
+  "exports": {
+    ".": {
+      "default": "./dist/index.js",
+      "types": "./types/index.d.ts"
+    }
+  }
+}
+// @filename: index.ts
+export {srcthing as thing} from "./src/thing.js";
+// @filename: src/thing.ts
+// The following import should cause `index.ts`
+// to be included in the build, which will,
+// in turn, cause the common src directory to not be `src`
+// (the harness is wierd here in that noImplicitReferences makes only
+// this file get loaded as an entrypoint and emitted, while on the
+// real command-line we'll crawl the imports for that set - a limitation
+// of the harness, I suppose)
+import * as me from "@this/package";
+
+me.thing();
+
+export function srcthing(): void {}
+

tests/cases/compiler/nodeNextPackageSelfNameWithOutDirDeclDirRootDir.ts

@@ -0,0 +1,22 @@
+// @module: nodenext
+// @outDir: /pkg/dist
+// @declarationDir: /pkg/types
+// @declaration: true
+// @rootDir: /pkg/src
+// @filename: /pkg/package.json
+{
+  "name": "@this/package",
+  "type": "module",
+  "exports": {
+    ".": {
+      "default": "./dist/index.js",
+      "types": "./types/index.d.ts"
+    }
+  }
+}
+// @filename: /pkg/src/index.ts
+import * as me from "@this/package";
+
+me.thing();
+
+export function thing(): void {}

tests/cases/compiler/nodeNextPackageSelfNameWithOutDirRootDir.ts

@@ -0,0 +1,17 @@
+// @module: nodenext
+// @outDir: ./dist
+// @rootDir: tests/cases/compiler
+// @filename: package.json
+{
+  "name": "@this/package",
+  "type": "module",
+  "exports": {
+    ".": "./dist/index.js"
+  }
+}
+// @filename: index.ts
+import * as me from "@this/package";
+
+me.thing();
+
+export function thing(): void {}