有个项目在mac下开发，安装包npm i，一切正常；

把这个项目放到linux机器上，安装包npm i，报了一堆warning：

npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@^1.2.7 (node_modules/chokidar/node_modules/fsevents):npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.7: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})npm WARN 0403@1.0.0 No descriptionnpm WARN 0403@1.0.0 No repository field.npm WARN optional SKIPPING OPTIONAL DEPENDENCY: abbrev@1.1.1 (node_modules/fsevents/node_modules/abbrev):npm WARN enoent SKIPPING OPTIONAL DEPENDENCY: ENOENT: no such file or directory, rename '/root/2019/0403/node_modules/fsevents/node_modules/abbrev' -> '/root/2019/0403/node_modules/fsevents/node_modules/.abbrev.DELETE'npm WARN optional SKIPPING OPTIONAL DEPENDENCY: ansi-regex@2.1.1 (node_modules/fsevents/node_modules/ansi-regex):npm WARN enoent SKIPPING OPTIONAL DEPENDENCY: ENOENT: no such file or directory, rename '/root/2019/0403/node_modules/fsevents/node_modules/ansi-regex' -> '/root/2019/0403/node_modules/fsevents/node_modules/.ansi-regex.DELETE'npm WARN optional SKIPPING OPTIONAL DEPENDENCY: aproba@1.2.0 (node_modules/fsevents/node_modules/aproba):npm WARN enoent SKIPPING OPTIONAL DEPENDENCY: ENOENT: no such file or directory, rename '/root/2019/0403/node_modules/fsevents/node_modules/aproba' -> '/root/2019/0403/node_modules/fsevents/node_modules/.aproba.DELETE'npm WARN optional SKIPPING OPTIONAL DEPENDENCY: balanced-match@1.0.0 (node_modules/fsevents/node_modules/balanced-match):npm WARN enoent SKIPPING OPTIONAL DEPENDENCY: ENOENT: no such file or directory, rename '/root/2019/0403/node_modules/fsevents/node_modules/balanced-match' -> '/root/2019/0403/node_modules/fsevents/node_modules/.balanced-match.DELETE'npm WARN optional SKIPPING OPTIONAL DEPENDENCY: chownr@1.1.1 (node_modules/fsevents/node_modules/chownr):npm WARN enoent SKIPPING OPTIONAL DEPENDENCY: ENOENT: no such file or directory, rename '/root/2019/0403/node_modules/fsevents/node_modules/chownr' -> '/root/2019/0403/node_modules/fsevents/node_modules/.chownr.DELETE'npm WARN optional SKIPPING OPTIONAL DEPENDENCY: code-point-at@1.1.0 (node_modules/fsevents/node_modules/code-point-at):npm WARN enoent SKIPPING OPTIONAL DEPENDENCY: ENOENT: no such file or directory, rename '/root/2019/0403/node_modules/fsevents/node_modules/code-point-at' -> '/root/2019/0403/node_modules/fsevents/node_modules/.code-point-at.DELETE'...

执行npm ls，有不少UNMET OPTIONAL DEPENDENCY的模块，最后还报了一堆错：

│ ├── define-property@2.0.2 deduped│ ├── extend-shallow@3.0.2 deduped│ ├── regex-not@1.0.2 deduped│ └─┬ safe-regex@1.1.0│ └── ret@0.1.15├─┬ UNMET OPTIONAL DEPENDENCY fsevents@1.2.7│ ├── nan@2.13.2│ └─┬ UNMET OPTIONAL DEPENDENCY node-pre-gyp@0.10.3│ ├── UNMET OPTIONAL DEPENDENCY detect-libc@1.0.3│ ├─┬ UNMET DEPENDENCY mkdirp@0.5.1│ │ └── UNMET DEPENDENCY minimist@0.0.8│ ├─┬ UNMET OPTIONAL DEPENDENCY needle@2.2.4│ │ ├─┬ UNMET OPTIONAL DEPENDENCY debug@2.6.9│ │ │ └── UNMET OPTIONAL DEPENDENCY ms@2.0.0│ │ ├─┬ UNMET OPTIONAL DEPENDENCY iconv-lite@0.4.24│ │ │ └── UNMET OPTIONAL DEPENDENCY safer-buffer@2.1.2│ │ └── UNMET OPTIONAL DEPENDENCY sax@1.2.4│ ├─┬ UNMET OPTIONAL DEPENDENCY nopt@4.0.1│ │ ├── UNMET OPTIONAL DEPENDENCY abbrev@1.1.1│ │ └─┬ UNMET OPTIONAL DEPENDENCY osenv@0.1.5│ │ ├── UNMET OPTIONAL DEPENDENCY os-homedir@1.0.2│ │ └── UNMET OPTIONAL DEPENDENCY os-tmpdir@1.0.2│ ├─┬ UNMET OPTIONAL DEPENDENCY npm-packlist@1.2.0│ │ ├─┬ UNMET OPTIONAL DEPENDENCY ignore-walk@3.0.1│ │ │ └─┬ UNMET DEPENDENCY minimatch@3.0.4│ │ │ └─┬ UNMET DEPENDENCY brace-expansion@1.1.11│ │ │ ├── UNMET DEPENDENCY balanced-match@1.0.0│ │ │ └── UNMET DEPENDENCY concat-map@0.0.1│ │ └── UNMET OPTIONAL DEPENDENCY npm-bundled@1.0.5│ ├─┬ UNMET OPTIONAL DEPENDENCY npmlog@4.1.2│ │ ├─┬ UNMET OPTIONAL DEPENDENCY are-we-there-yet@1.1.5│ │ │ ├── UNMET OPTIONAL DEPENDENCY delegates@1.0.0│ │ │ └─┬ UNMET OPTIONAL DEPENDENCY readable-stream@2.3.6│ │ │ ├── UNMET OPTIONAL DEPENDENCY core-util-is@1.0.2│ │ │ ├── UNMET DEPENDENCY inherits@2.0.3│ │ │ ├── UNMET OPTIONAL DEPENDENCY isarray@1.0.0│ │ │ ├── UNMET OPTIONAL DEPENDENCY process-nextick-args@2.0.0│ │ │ ├── UNMET DEPENDENCY safe-buffer@5.1.2│ │ │ ├─┬ UNMET OPTIONAL DEPENDENCY string_decoder@1.1.1│ │ │ │ └── UNMET DEPENDENCY safe-buffer@5.1.2│ │ │ └── UNMET OPTIONAL DEPENDENCY util-deprecate@1.0.2│ │ ├── UNMET DEPENDENCY console-control-strings@1.1.0│ │ ├─┬ UNMET OPTIONAL DEPENDENCY gauge@2.7.4│ │ │ ├── UNMET OPTIONAL DEPENDENCY aproba@1.2.0│ │ │ ├── UNMET DEPENDENCY console-control-strings@1.1.0│ │ │ ├── UNMET OPTIONAL DEPENDENCY has-unicode@2.0.1│ │ │ ├── UNMET OPTIONAL DEPENDENCY object-assign@4.1.1│ │ │ ├── UNMET OPTIONAL DEPENDENCY signal-exit@3.0.2│ │ │ ├─┬ UNMET DEPENDENCY string-width@1.0.2│ │ │ │ ├── UNMET DEPENDENCY code-point-at@1.1.0│ │ │ │ ├─┬ UNMET DEPENDENCY is-fullwidth-code-point@1.0.0│ │ │ │ │ └── UNMET DEPENDENCY number-is-nan@1.0.1│ │ │ │ └── UNMET DEPENDENCY strip-ansi@3.0.1│ │ │ ├─┬ UNMET DEPENDENCY strip-ansi@3.0.1│ │ │ │ └── UNMET DEPENDENCY ansi-regex@2.1.1│ │ │ └─┬ UNMET OPTIONAL DEPENDENCY wide-align@1.1.3│ │ │ └── UNMET DEPENDENCY string-width@1.0.2│ │ └── UNMET OPTIONAL DEPENDENCY set-blocking@2.0.0│ ├─┬ UNMET OPTIONAL DEPENDENCY rc@1.2.8│ │ ├── UNMET OPTIONAL DEPENDENCY deep-extend@0.6.0│ │ ├── UNMET OPTIONAL DEPENDENCY ini@1.3.5│ │ ├── UNMET OPTIONAL DEPENDENCY minimist@1.2.0│ │ └── UNMET OPTIONAL DEPENDENCY strip-json-comments@2.0.1│ ├─┬ UNMET OPTIONAL DEPENDENCY rimraf@2.6.3│ │ └─┬ UNMET OPTIONAL DEPENDENCY glob@7.1.3│ │ ├── UNMET OPTIONAL DEPENDENCY fs.realpath@1.0.0│ │ ├─┬ UNMET OPTIONAL DEPENDENCY inflight@1.0.6│ │ │ ├── UNMET DEPENDENCY once@1.4.0│ │ │ └── UNMET DEPENDENCY wrappy@1.0.2│ │ ├── UNMET DEPENDENCY inherits@2.0.3│ │ ├── UNMET DEPENDENCY minimatch@3.0.4│ │ ├─┬ UNMET DEPENDENCY once@1.4.0│ │ │ └── UNMET DEPENDENCY wrappy@1.0.2│ │ └── UNMET OPTIONAL DEPENDENCY path-is-absolute@1.0.1│ ├── UNMET OPTIONAL DEPENDENCY semver@5.6.0│ └─┬ UNMET OPTIONAL DEPENDENCY tar@4.4.8│ ├── UNMET OPTIONAL DEPENDENCY chownr@1.1.1│ ├─┬ UNMET OPTIONAL DEPENDENCY fs-minipass@1.2.5│ │ └── UNMET DEPENDENCY minipass@2.3.5│ ├─┬ UNMET DEPENDENCY minipass@2.3.5│ │ ├── UNMET DEPENDENCY safe-buffer@5.1.2│ │ └── UNMET DEPENDENCY yallist@3.0.3│ ├─┬ UNMET OPTIONAL DEPENDENCY minizlib@1.2.1│ │ └── UNMET DEPENDENCY minipass@2.3.5│ ├── UNMET DEPENDENCY mkdirp@0.5.1│ ├── UNMET DEPENDENCY safe-buffer@5.1.2│ └── UNMET DEPENDENCY yallist@3.0.3├─┬ glob-parent@3.1.0│ ├─┬ is-glob@3.1.0│ │ └── is-extglob@2.1.1 deduped│ └── path-dirname@1.0.2├── inherits@2.0.3├─┬ is-binary-path@1.0.1│ └── binary-extensions@1.13.1├─┬ is-glob@4.0.1│ └── is-extglob@2.1.1├── normalize-path@3.0.0├── path-is-absolute@1.0.1├─┬ readdirp@2.2.1│ ├── graceful-fs@4.1.15│ ├── micromatch@3.1.10 deduped│ └─┬ readable-stream@2.3.6│ ├── core-util-is@1.0.2│ ├── inherits@2.0.3 deduped│ ├── isarray@1.0.0│ ├── process-nextick-args@2.0.0│ ├── safe-buffer@5.1.2│ ├─┬ string_decoder@1.1.1│ │ └── safe-buffer@5.1.2 deduped│ └── util-deprecate@1.0.2└── upath@1.1.2npm ERR! missing: mkdirp@0.5.1, required by node-pre-gyp@0.10.3npm ERR! missing: minimist@0.0.8, required by mkdirp@0.5.1npm ERR! missing: minimatch@3.0.4, required by ignore-walk@3.0.1npm ERR! missing: brace-expansion@1.1.11, required by minimatch@3.0.4npm ERR! missing: balanced-match@1.0.0, required by brace-expansion@1.1.11npm ERR! missing: concat-map@0.0.1, required by brace-expansion@1.1.11npm ERR! missing: console-control-strings@1.1.0, required by npmlog@4.1.2npm ERR! missing: inherits@2.0.3, required by readable-stream@2.3.6npm ERR! missing: safe-buffer@5.1.2, required by readable-stream@2.3.6npm ERR! missing: safe-buffer@5.1.2, required by string_decoder@1.1.1npm ERR! missing: console-control-strings@1.1.0, required by gauge@2.7.4npm ERR! missing: string-width@1.0.2, required by gauge@2.7.4npm ERR! missing: strip-ansi@3.0.1, required by gauge@2.7.4npm ERR! missing: code-point-at@1.1.0, required by string-width@1.0.2npm ERR! missing: is-fullwidth-code-point@1.0.0, required by string-width@1.0.2npm ERR! missing: strip-ansi@3.0.1, required by string-width@1.0.2npm ERR! missing: number-is-nan@1.0.1, required by is-fullwidth-code-point@1.0.0npm ERR! missing: ansi-regex@2.1.1, required by strip-ansi@3.0.1npm ERR! missing: string-width@1.0.2, required by wide-align@1.1.3npm ERR! missing: inherits@2.0.3, required by glob@7.1.3npm ERR! missing: minimatch@3.0.4, required by glob@7.1.3npm ERR! missing: once@1.4.0, required by glob@7.1.3npm ERR! missing: once@1.4.0, required by inflight@1.0.6npm ERR! missing: wrappy@1.0.2, required by inflight@1.0.6npm ERR! missing: wrappy@1.0.2, required by once@1.4.0npm ERR! missing: minipass@2.3.5, required by tar@4.4.8npm ERR! missing: mkdirp@0.5.1, required by tar@4.4.8npm ERR! missing: safe-buffer@5.1.2, required by tar@4.4.8npm ERR! missing: yallist@3.0.3, required by tar@4.4.8npm ERR! missing: minipass@2.3.5, required by fs-minipass@1.2.5npm ERR! missing: safe-buffer@5.1.2, required by minipass@2.3.5npm ERR! missing: yallist@3.0.3, required by minipass@2.3.5npm ERR! missing: minipass@2.3.5, required by minizlib@1.2.1

仔细观察发现UNMET OPTIONAL DEPENDENCY的模块和npm ERR是同一批模块，也是安装时报warning的那些模块。

再仔细观察发现这些都是fsevents依赖的模块。

fsevents只能在macOS下安装，无法在linux系统安装。linux下会跳过fsevents模块，也不会安装fsevents依赖的模块。

这其实算是npm的一个bug，npm i时报Warn，npm ls又报Err，前后不一致，容易有误解。

目前无论用哪个版本的npm都会有这个问题，npm i --no-optional也不能解决这个问题。

这些报错不影响项目的正常运行，因为linux不需要fsevents。

如果不希望看到npm Err，可以用npm i -f强制安装，安装过程没有warn，安装完后npm ls看下：

└─┬ chokidar@2.1.5└── fsevents@1.2.7

干净了，没有任何报错。

我的项目是chokidar这个模块依赖了fsevents，chokidar又是browser-sync、webpack等依赖的。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。