参考所有分组：保持OPFS备份失败非致命

结论：按 LinuxCNC rs274ngc_pre.cc save_parameters() 中 unlink/link 失败不阻止 rename 主参数文件的语义，OPFS 参数 .bak 写入失败时不让解析保存失败，并避免把目录当作可 unlink 的备份文件删除；未扩展 smoke 解析行为。

验证：./test-native.sh；./test-linuxcnc-source-link.sh；./test-web-wasm-browser-smoke.sh。

web/src/wasm-core.js

@@ -141,6 +141,21 @@ async function removeOpfsEntry(workspacePath, relativePath, recursive) {
   }
 }
 
+async function removeOpfsFileEntry(workspacePath, relativePath) {
+  assertRelativePath(relativePath);
+  const parts = relativePath.split("/");
+  const entryName = parts.pop();
+  try {
+    const directory = await getOpfsDirectoryHandle([workspacePath, ...parts].filter(Boolean).join("/"), false);
+    await directory.getFileHandle(entryName, { create: false });
+    await directory.removeEntry(entryName, { recursive: false });
+  } catch (error) {
+    if (error?.name !== "NotFoundError" && error?.name !== "TypeMismatchError") {
+      throw error;
+    }
+  }
+}
+
 async function opfsEntryExists(workspacePath, relativePath) {
   assertRelativePath(relativePath);
   const parts = relativePath.split("/");
@@ -498,7 +513,7 @@ function installOpfsWorkspace(module, options) {
       if (backupData !== null) {
         await writeOpfsFile(workspacePath, `${path}.bak`, backupData);
       } else {
-        await removeOpfsEntry(workspacePath, `${path}.bak`, false);
+        await removeOpfsFileEntry(workspacePath, `${path}.bak`);
       }
       return data;
     },
@@ -712,9 +727,22 @@ export async function createWasmSimulator(moduleOptions = {}) {
         // replacing filename. Browser filesystems may not expose that link
         // through the WASM mirror, so preserve the loaded OPFS file here.
         if (previousParameterFile === null) {
+          try {
+            const backupStat = await opfs.stat(`${parameterPath}.bak`);
+            if (backupStat.kind === "file") {
               await opfs.removeFile(`${parameterPath}.bak`);
+            }
+          } catch (error) {
+            if (error?.name !== "NotFoundError") {
+              throw error;
+            }
+          }
         } else {
+          try {
             await opfs.writeFile(`${parameterPath}.bak`, previousParameterFile);
+          } catch (_backupError) {
+            // LinuxCNC treats link(filename, filename + ".bak") failure as non-fatal.
+          }
         }
         return events;
       } finally {

web/test-browser-wasm-smoke-opfs-parameter-sections.js

@@ -6,6 +6,7 @@ export async function runBrowserOpfsParameterSections(context, simulator) {
     expectMissingOpfsFile,
     expectMissingWasmPath,
     expectNoEvent,
+    expectOpfsDirectoryStat,
     expectText,
     expectWasmFilesMissing,
     near,
@@ -15,14 +16,11 @@ export async function runBrowserOpfsParameterSections(context, simulator) {
     withSmokeSimulator,
   } = context;
   const backend = { backend: "linuxcnc-rs274" };
+  const parseWithParameters = (program, path) =>
+    simulator.parseWithParameterFile(program, path, "linuxcnc", backend);
 
   await runSection("opfs parameter save", async () => {
-    await simulator.parseWithParameterFile(
+    await simulator.parseWithParameterFile("G21 G90\nG0 X1\nG28.1\nM30\n", "parameters/rs274ngc.var", "linuxcnc", backend);
-      "G21 G90\nG0 X1\nG28.1\nM30\n",
-      "parameters/rs274ngc.var",
-      "linuxcnc",
-      backend,
-    );
     const opfsParameterFile = await readOpfsText(simulator, "parameters/rs274ngc.var");
     expectIncludes(opfsParameterFile, "5161\t1.000000", "LinuxCNC parameter file was not persisted into OPFS");
   });
@@ -45,12 +43,7 @@ export async function runBrowserOpfsParameterSections(context, simulator) {
   await runSection("opfs default parameter backup", async () => {
     // LinuxCNC source basis: rs274ngc_pre.cc save_parameters()
     // preserves the previous default parameter file as filename + ".bak".
-    await simulator.parseWithParameterFile(
+    await parseWithParameters("G21 G90\nM30\n", "parameters/rs274ngc.var");
-      "G21 G90\nM30\n",
-      "parameters/rs274ngc.var",
-      "linuxcnc",
-      backend,
-    );
     const defaultParameterBackup = await readOpfsText(simulator, "parameters/rs274ngc.var.bak");
     expectIncludes(defaultParameterBackup, "5161\t1.000000", "LinuxCNC default OPFS parameter backup did not preserve the previous file");
   });
@@ -60,11 +53,9 @@ export async function runBrowserOpfsParameterSections(context, simulator) {
     // LinuxCNC source basis: rs274ngc_pre.cc save_parameters() writes
     // filename + ".new", then renames it over the parameter file.
     simulator.fs.module.FS.writeFile("rs274ngc.var.new", "stale wasm temporary parameter file\n");
-    const restoredParameterEvents = await simulator.parseWithParameterFile(
+    const restoredParameterEvents = await parseWithParameters(
       "G21 G90\nF100\nO10 if [#5161 EQ 1]\nG1 X9\nO10 endif\n",
       "parameters/rs274ngc.var",
-      "linuxcnc",
-      backend,
     );
     expectEvent(restoredParameterEvents, (event) => event.type === "linear-feed" && near(event.end.x, 9),
       "LinuxCNC parameter file was not restored from OPFS");
@@ -97,12 +88,7 @@ export async function runBrowserOpfsParameterSections(context, simulator) {
     // LinuxCNC source basis: rs274ngc_pre.cc save_parameters() unlinks
     // filename + ".bak", links the current parameter file to it,
     // then renames filename + ".new" over filename.
-    await simulator.parseWithParameterFile(
+    await parseWithParameters("G21 G90\nG0 X4\nG28.1\nM30\n", "parameters/existing-save.var");
-      "G21 G90\nG0 X4\nG28.1\nM30\n",
-      "parameters/existing-save.var",
-      "linuxcnc",
-      backend,
-    );
     const existingSaveParameterFile = await readOpfsText(simulator, "parameters/existing-save.var");
     expectIncludes(existingSaveParameterFile, "5161\t4.000000", "LinuxCNC existing OPFS parameter file was not replaced after save");
     const existingSaveParameterBackup = await readOpfsText(simulator, "parameters/existing-save.var.bak");
@@ -111,6 +97,15 @@ export async function runBrowserOpfsParameterSections(context, simulator) {
       () => simulator.fs.opfs.readFile("parameters/existing-save.var.new"),
       "LinuxCNC existing OPFS parameter temporary file remained after save",
     );
+    await simulator.fs.opfs.writeFile("parameters/backup-directory.var", "5161\t6.000000\n");
+    const backupDirectory = simulator.fs.opfs.resolvePath("parameters/backup-directory.var.bak");
+    simulator.fs.module.FS.mkdir(backupDirectory);
+    await simulator.fs.opfs.persistDirectory("parameters/backup-directory.var.bak");
+    await parseWithParameters("G21 G90\nG0 X7\nG28.1\nM30\n", "parameters/backup-directory.var");
+    expectIncludes(await readOpfsText(simulator, "parameters/backup-directory.var"), "5161\t7.000000",
+      "LinuxCNC OPFS parameter file was not saved when backup link failed");
+    await expectOpfsDirectoryStat(simulator, "parameters/backup-directory.var.bak",
+      "LinuxCNC non-fatal OPFS backup failure did not leave the existing backup path intact");
   });
 
   await runSection("opfs parameter stale backup cleanup", async () => {