Fix valid check, tree-shaking and binding trace

Author: lxsmnsyc

packages/start/src/directives/compile.ts

@@ -1,5 +1,5 @@
-import path from "node:path";
 import * as babel from "@babel/core";
+import path from "node:path";
 import { directivesPlugin, type StateContext } from "./plugin.ts";
 import xxHash32 from "./xxhash32.ts";
 
@@ -9,23 +9,21 @@ export interface CompileResult {
   map: babel.BabelFileResult["map"];
 }
 
-export type CompileOptions = Omit<StateContext, "count" | "hash" | "imports">;
+export type CompileOptions = Omit<StateContext, "count" | "hash" | "imports" | "valid">;
 
 export async function compile(
   id: string,
   code: string,
   options: CompileOptions,
 ): Promise<CompileResult> {
   const context: StateContext = {
-      ...options,
-      hash: xxHash32(id).toString(16),
-      count: 0,
-      imports: new Map(),
-    } 
-  const pluginOption = [
-    directivesPlugin,
-    context,
-  ];
+    ...options,
+    valid: false,
+    hash: xxHash32(id).toString(16),
+    count: 0,
+    imports: new Map(),
+  };
+  const pluginOption = [directivesPlugin, context];
   const plugins: NonNullable<NonNullable<babel.TransformOptions["parserOpts"]>["plugins"]> = [
     "jsx",
   ];
@@ -47,7 +45,7 @@ export async function compile(
 
   if (result) {
     return {
-      valid: context.count > 0,
+      valid: context.valid,
       code: result.code || "",
       map: result.map,
     };

packages/start/src/directives/plugin.ts

@@ -18,6 +18,7 @@ export interface StateContext {
   hash: string;
   count: number;
   imports: Map<string, t.Identifier>;
+  valid: boolean;
 
   definitions: {
     register: ImportDefinition;
@@ -146,7 +147,12 @@ function traceBinding(path: babel.NodePath, name: string): Binding | undefined {
           if (right) {
             return traceBinding(path, right.node.name);
           }
-          return current;
+
+          // Only valid for functions
+          const func = unwrapPath(current.path.get('init'), isValidFunction);
+          if (func) {
+            return current;
+          }
         }
       }
       return undefined;
@@ -329,10 +335,16 @@ function transformModuleLevelDirective(ctx: StateContext, program: babel.NodePat
       }
     }
 
-    program.pushContainer("body", [
-      t.variableDeclaration("const", declarations),
-      t.exportNamedDeclaration(null, specifiers, null),
-    ]);
+    const body: t.Statement[] = [];
+
+    if (declarations.length > 0) {
+      body.push(t.variableDeclaration("const", declarations));
+    }
+    if (specifiers.length > 0) {
+      body.push(t.exportNamedDeclaration(null, specifiers, null));
+    }
+
+    program.pushContainer("body", body);
   }
 }
 
@@ -344,6 +356,7 @@ export function directivesPlugin(): babel.PluginObj<State> {
         const isModuleLevel = isDirectiveValid(ctx.opts, program.node.directives);
         if (isModuleLevel) {
           transformModuleLevelDirective(ctx.opts, program);
+          ctx.opts.valid = true;
         } else {
           // First, bubble up function declarations
           program.traverse({
@@ -366,6 +379,7 @@ export function directivesPlugin(): babel.PluginObj<State> {
           program.scope.crawl();
 
           if (ctx.opts.count > 0) {
+            ctx.opts.valid = true;
             removeUnusedVariables(program);
           }
         }

packages/start/src/directives/remove-unused-variables.ts

@@ -1,5 +1,6 @@
 import type * as babel from "@babel/core";
-import type * as t from "@babel/types";
+import * as t from "@babel/types";
+import { isPathValid } from "./paths.ts";
 
 export function removeUnusedVariables(program: babel.NodePath<t.Program>) {
   // TODO(Alexis):
@@ -23,7 +24,16 @@ export function removeUnusedVariables(program: babel.NodePath<t.Program>) {
             case "hoisted":
             case "module":
               if (binding.references === 0 && !binding.path.removed) {
-                binding.path.remove();
+                if (isPathValid(path.parentPath, t.isImportDeclaration)) {
+                  const parent = path.parentPath;
+                  if (parent.node.specifiers.length === 1) {
+                    parent.remove();
+                  } else {
+                    binding.path.remove();
+                  }
+                } else {
+                  binding.path.remove();
+                }
                 dirty = true;
               }
               break;
@@ -34,6 +44,11 @@ export function removeUnusedVariables(program: babel.NodePath<t.Program>) {
           }
         }
       },
+      VariableDeclaration(path) {
+        if (path.node.declarations.length === 0) {
+          path.remove();
+        }
+      },
     });
     program.scope.crawl();
   }