feat: add extract core wasm command

Signed-off-by: Gordon Smith <GordonJSmith@gmail.com>

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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: GordonSmith

package.json

@@ -172,6 +172,11 @@
                 "command": "wit-idl.extractWit",
                 "title": "Extract WIT",
                 "category": "WIT"
+            },
+            {
+                "command": "wit-idl.extractCoreWasm",
+                "title": "Extract Core Wasm",
+                "category": "WIT"
             }
         ],
         "submenus": [
@@ -190,29 +195,39 @@
                 {
                     "submenu": "wit-idl.generateBindings.submenu",
                     "when": "resourceExtname == .wit || witIdl.isWasmComponent",
-                    "group": "navigation"
+                    "group": "navigation@12"
                 },
                 {
                     "command": "wit-idl.extractWit",
                     "when": "resourceExtname == .wasm && witIdl.isWasmComponent",
-                    "group": "navigation"
+                    "group": "navigation@10"
+                },
+                {
+                    "command": "wit-idl.extractCoreWasm",
+                    "when": "resourceExtname == .wasm && witIdl.isWasmComponent",
+                    "group": "navigation@11"
                 }
             ],
             "explorer/context": [
                 {
                     "command": "wit-idl.syntaxCheck",
                     "when": "resourceExtname == .wit",
-                    "group": "navigation"
+                    "group": "4_witIdl@10"
                 },
                 {
-                    "submenu": "wit-idl.generateBindings.submenu",
-                    "when": "resourceExtname == .wit || witIdl.isWasmComponent",
-                    "group": "navigation"
+                    "command": "wit-idl.extractWit",
+                    "when": "resourceExtname == .wasm && witIdl.isWasmComponent",
+                    "group": "4_witIdl@11"
                 },
                 {
-                    "command": "wit-idl.extractWit",
+                    "command": "wit-idl.extractCoreWasm",
                     "when": "resourceExtname == .wasm && witIdl.isWasmComponent",
-                    "group": "navigation"
+                    "group": "4_witIdl@12"
+                },
+                {
+                    "submenu": "wit-idl.generateBindings.submenu",
+                    "when": "resourceExtname == .wit || witIdl.isWasmComponent",
+                    "group": "4_witIdl@13"
                 }
             ],
             "wit-idl.generateBindings.submenu": [
@@ -266,6 +281,10 @@
                 {
                     "command": "wit-idl.extractWit",
                     "when": "witIdl.isWasmComponent"
+                },
+                {
+                    "command": "wit-idl.extractCoreWasm",
+                    "when": "witIdl.isWasmComponent"
                 }
             ]
         },

src/extension.ts

@@ -3,7 +3,12 @@ import * as path from "path";
 import * as fs from "fs";
 import { WitSyntaxValidator } from "./validator.js";
 import { isWasmComponentFile } from "./wasmDetection.js";
-import { getWitBindgenVersionFromWasm, extractWitFromComponent, generateBindingsFromWasm } from "./wasmUtils.js";
+import {
+    getWitBindgenVersionFromWasm,
+    extractWitFromComponent,
+    generateBindingsFromWasm,
+    extractCoreWasmFromComponent,
+} from "./wasmUtils.js";
 
 // Removed: openExtractedWitDocument - we now render a readonly view in a custom editor
 
@@ -369,6 +374,105 @@ export function activate(context: vscode.ExtensionContext) {
         }
     });
 
+    // Implement extractCoreWasm command
+    const extractCoreWasmCommand = vscode.commands.registerCommand(
+        "wit-idl.extractCoreWasm",
+        async (resource?: vscode.Uri) => {
+            try {
+                const targetUri: vscode.Uri | undefined = resource ?? vscode.window.activeTextEditor?.document.uri;
+                if (!targetUri) {
+                    vscode.window.showErrorMessage("No file selected.");
+                    return;
+                }
+
+                const filePath: string = targetUri.fsPath;
+                if (!filePath.toLowerCase().endsWith(".wasm")) {
+                    vscode.window.showErrorMessage("Selected file is not a .wasm file.");
+                    return;
+                }
+
+                const isComp: boolean = await isWasmComponent(filePath);
+                if (!isComp) {
+                    vscode.window.showWarningMessage("The selected .wasm is not a WebAssembly component.");
+                    return;
+                }
+
+                // Extract using embedded wasm-utils (no external CLI dependency)
+                const bytes = await vscode.workspace.fs.readFile(targetUri);
+                const fileMap = await extractCoreWasmFromComponent(bytes);
+                const entries = Object.entries(fileMap).sort(([a], [b]) =>
+                    a.localeCompare(b, undefined, { numeric: true, sensitivity: "base" })
+                );
+                if (entries.length === 0) {
+                    vscode.window.showWarningMessage("No core wasm modules found in this component.");
+                    return;
+                }
+
+                let [chosenName, chosenContent] = entries[0];
+                if (entries.length > 1) {
+                    const pick = await vscode.window.showQuickPick(
+                        entries.map(([name]) => name),
+                        {
+                            placeHolder: "Multiple core wasm modules found. Select one to save.",
+                        }
+                    );
+                    if (!pick) {
+                        return;
+                    }
+                    const found = entries.find(([name]) => name === pick);
+                    if (found) {
+                        [chosenName, chosenContent] = found;
+                    }
+                }
+
+                // Now we know which core module is selected, propose a default filename that includes it
+                const baseName: string = path.basename(filePath, ".wasm");
+                const defaultFileName: string = `${baseName}.${chosenName}`; // e.g., mycomp.core0.wasm
+                const defaultDir: string = path.dirname(filePath);
+                const saveUri = await vscode.window.showSaveDialog({
+                    title: "Save extracted Core Wasm",
+                    defaultUri: vscode.Uri.file(path.join(defaultDir, defaultFileName)),
+                    filters: { WebAssembly: ["wasm"], "All Files": ["*"] },
+                });
+                if (!saveUri) {
+                    return;
+                }
+
+                // Write selected core wasm to the chosen path
+                const data = chosenContent; // already Uint8Array
+                try {
+                    await vscode.workspace.fs.stat(saveUri);
+                    const choice = await vscode.window.showWarningMessage(
+                        `File already exists: ${saveUri.fsPath}. Overwrite?`,
+                        { modal: true },
+                        "Overwrite",
+                        "Cancel"
+                    );
+                    if (choice !== "Overwrite") {
+                        return;
+                    }
+                } catch {
+                    // stat throws if file doesn't exist; continue
+                }
+                await vscode.workspace.fs.writeFile(saveUri, data);
+
+                vscode.window.showInformationMessage(`Core wasm extracted to ${saveUri.fsPath}`);
+                try {
+                    await vscode.commands.executeCommand("vscode.open", saveUri);
+                } catch (openError) {
+                    vscode.window.showWarningMessage(
+                        `Core wasm was extracted and saved to ${saveUri.fsPath}, but could not be opened automatically. You can open it manually (e.g., with "Open With... Hex Editor").`
+                    );
+                }
+            } catch (error) {
+                console.error("extractCoreWasm failed:", error);
+                vscode.window.showErrorMessage(
+                    `Failed to extract core wasm: ${error instanceof Error ? error.message : String(error)}`
+                );
+            }
+        }
+    );
+
     /**
      * Create a binding generation command for a specific language
      * @param language - The target language for bindings
@@ -625,6 +729,7 @@ export function activate(context: vscode.ExtensionContext) {
         syntaxCheckWorkspaceCommand,
         showVersionCommand,
         extractWitCommand,
+        extractCoreWasmCommand,
         generateRustBindingsCommand,
         generateCBindingsCommand,
         generateCSharpBindingsCommand,

src/wasmUtils.ts

@@ -149,6 +149,41 @@ export async function extractWitFromComponent(bytes: Uint8Array): Promise<string
     }
 }
 
+/**
+ * Extract core wasm module(s) from a WebAssembly component using the WASM module.
+ * Returns a filename -> binary bytes map. Empty map on failure or none found.
+ */
+export async function extractCoreWasmFromComponent(bytes: Uint8Array): Promise<Record<string, Uint8Array>> {
+    if (!wasmModule) {
+        await initializeWasm();
+    }
+    if (!wasmModule) {
+        throw new Error("WASM module not initialized");
+    }
+
+    function hasExtractCore(obj: unknown): obj is { extractCoreWasmFromComponent: (data: Uint8Array) => string } {
+        return typeof (obj as { extractCoreWasmFromComponent?: unknown }).extractCoreWasmFromComponent === "function";
+    }
+
+    const instance = new wasmModule.WitBindgen();
+    try {
+        if (!hasExtractCore(instance)) {
+            throw new Error("extractCoreWasmFromComponent not available in wit-bindgen-wasm module");
+        }
+        const json = instance.extractCoreWasmFromComponent(bytes);
+        const textMap = JSON.parse(json || "{}") as Record<string, string>;
+        // Decode into binary bytes (latin1-to-bytes convention from WASM side)
+        const result: Record<string, Uint8Array> = {};
+        for (const [name, content] of Object.entries(textMap)) {
+            // Buffer.from with 'latin1' yields the original byte values 0..255
+            result[name] = Buffer.from(content, "latin1");
+        }
+        return result;
+    } finally {
+        instance.free();
+    }
+}
+
 /**
  * Extract interfaces from WIT content using the WASM module
  * @param content - The WIT content to parse

tests/commands.test.ts

@@ -0,0 +1,42 @@
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+import { describe, it, expect } from "vitest";
+
+type Command = { command: string };
+type MenuItem = { command?: string; when?: string };
+type Contributes = {
+    commands: Command[];
+    menus: Record<string, MenuItem[]> & { commandPalette: MenuItem[] };
+};
+
+describe("command contributions", () => {
+    const pkg = JSON.parse(readFileSync(join(__dirname, "..", "package.json"), "utf8")) as unknown as {
+        contributes: Contributes;
+    };
+
+    it("includes Extract Core Wasm command", () => {
+        const commands: Command[] = pkg.contributes.commands;
+        expect(commands.some((c) => c.command === "wit-idl.extractCoreWasm")).toBe(true);
+    });
+
+    it("shows Extract Core Wasm in explorer and editor context menus for wasm components", () => {
+        const menus = pkg.contributes.menus;
+        const hasInEditor = (menus["editor/context"] || []).some(
+            (m: MenuItem) =>
+                m.command === "wit-idl.extractCoreWasm" && !!m.when && /witIdl\.isWasmComponent/.test(m.when)
+        );
+        const hasInExplorer = (menus["explorer/context"] || []).some(
+            (m: MenuItem) =>
+                m.command === "wit-idl.extractCoreWasm" && !!m.when && /witIdl\.isWasmComponent/.test(m.when)
+        );
+        expect(hasInEditor).toBe(true);
+        expect(hasInExplorer).toBe(true);
+    });
+
+    it("shows Extract Core Wasm in command palette when component is active", () => {
+        const palette: MenuItem[] = pkg.contributes.menus.commandPalette;
+        const entry = palette.find((m: MenuItem) => m.command === "wit-idl.extractCoreWasm");
+        expect(entry).toBeTruthy();
+        expect(entry && entry.when ? /witIdl\.isWasmComponent/.test(entry.when) : false).toBe(true);
+    });
+});

wit-bindgen-wasm/Cargo.lock

@@ -18,6 +18,7 @@ wasm-bindgen = "0.2.100"
 wee_alloc = { version = "0.4.5", optional = true }
 console_error_panic_hook = { version = "0.1.6", optional = true }
 serde_json = "1.0"
+wasmparser = { version = "0.224", features = ["component-model"] }
 wit-parser = "0.236"
 wit-bindgen-core = "0.44"
 wit-bindgen-c = "0.44"