feat: add npm scoped-modules import resolution

src/ast/ast-constants.ts

@@ -70,6 +70,7 @@ export const astNumberBases = Object.freeze(
 const importTypesRecord: Record<Ast.ImportType, true> = {
     stdlib: true,
     relative: true,
+    package: true,
 };
 
 export const importTypes = Object.freeze(keys(importTypesRecord));

src/ast/ast.ts

@@ -596,7 +596,7 @@ export type ImportPath = {
 
 // This is different from ItemOrigin, because relative import
 // from standard library is still import with origin: "stdlib"
-export type ImportType = "stdlib" | "relative";
+export type ImportType = "stdlib" | "relative" | "package";
 
 // A String is a string in which escaping characters, like '\\' has been simplified, e.g., '\\' simplified to '\'.
 export type String = {

src/grammar/index.ts

@@ -1450,6 +1450,7 @@ const guessExtension = (
 };
 
 const stdlibPrefix = "@stdlib/";
+const packagePrefix = "@";
 
 const parseImportString =
     (importText: string, loc: $.Loc): Handler<Ast.ImportPath> =>
@@ -1478,6 +1479,20 @@ const parseImportString =
                 type: "stdlib",
                 language,
             };
+        } else if (guessedPath.startsWith(packagePrefix)) {
+            // TODO: support non-scoped npm packages
+            // (@package-name instead of @scope/package-name)
+            const path = fromString(guessedPath);
+
+            if (path.stepsUp !== 0) {
+                ctx.err.importWithBackslash()(loc);
+            }
+
+            return {
+                path,
+                type: "package",
+                language,
+            };
         } else if (
             guessedPath.startsWith("./") ||
             guessedPath.startsWith("../")

src/imports/resolveLibrary.spec.ts

@@ -7,6 +7,7 @@ const project = createVirtualFileSystem("/project", {
     ["main.tact"]: "",
     ["import.tact"]: "",
     ["main.fc"]: "",
+    ["node_modules/@name/j.tact"]: "",
 });
 
 const mainSource: Source = {
@@ -26,6 +27,26 @@ const stdlibSource: Source = {
     code: "",
 };
 
+it("project file, node_modules package import", () => {
+    const resolved = resolveLibrary({
+        sourceFrom: mainSource,
+        importPath: {
+            path: fromString("@name/j.tact"),
+            language: "tact",
+            type: "package",
+        },
+        project,
+        stdlib,
+    });
+
+    expect(resolved).toMatchObject({
+        ok: true,
+        path: "/project/node_modules/@name/j.tact",
+        origin: "user",
+        language: "tact",
+    });
+});
+
 it("project file, stdlib import", () => {
     const resolved = resolveLibrary({
         sourceFrom: mainSource,

src/imports/resolveLibrary.ts

@@ -2,6 +2,7 @@ import type * as Ast from "@/ast/ast";
 import type { VirtualFileSystem } from "@/vfs/VirtualFileSystem";
 import { asString } from "@/imports/path";
 import type { ItemOrigin, Language, Source } from "@/imports/source";
+import { repeat } from "@/utils/array";
 
 type ResolveLibraryArgs = {
     readonly importPath: Ast.ImportPath;
@@ -23,6 +24,38 @@ type ResolveLibraryFailure = {
 
 type ResolveLibraryResult = ResolveLibrarySuccess | ResolveLibraryFailure;
 
+const nodeModulesPath = "node_modules";
+
+const findIndentNodeModules = (
+    project: VirtualFileSystem,
+    root: string,
+    path: string,
+) => {
+    // TODO: unwind folders until we either
+    // find our import or reach project root
+    for (let index = 0; index < 20; index++) {
+        const tryRes = project.resolve(
+            root,
+            ...repeat("..", index),
+            nodeModulesPath,
+            path,
+        );
+
+        if (!project.exists(tryRes)) {
+            continue;
+        }
+
+        return {
+            ok: true,
+            path: tryRes,
+        };
+    }
+
+    return {
+        ok: false,
+    };
+};
+
 export function resolveLibrary({
     importPath,
     sourceFrom,
@@ -42,6 +75,23 @@ export function resolveLibrary({
         } else {
             return { ok: false };
         }
+    } else if (importPath.type === "package") {
+        const res = findIndentNodeModules(
+            project,
+            sourceFrom.path.slice(project.root.length),
+            asString(importPath.path),
+        );
+
+        if (res.ok) {
+            return {
+                ok: true,
+                path: res.path!,
+                origin: sourceFrom.origin,
+                language: importPath.language,
+            };
+        } else {
+            return { ok: false };
+        }
     } else {
         const vfs = sourceFrom.origin === "stdlib" ? stdlib : project;
         const resolvedPath = vfs.resolve(