rails webpacker:install実行したらエラーが。。

ターミナル

xxxx-no-MacBook-Pro:collabfield groovy$ rails webpacker:install
RAILS_ENV=development environment is not defined in config/webpacker.yml, falling back to production environment
rails aborted!
Webpacker configuration file not found /Users/xxxx/Desktop/rails_middle_tutorial/collabfield/config/webpacker.yml. Please run rails webpacker:install Error: No such file or directory @ rb_sysopen - /Users/xxxx/Desktop/rails_middle_tutorial/collabfield/config/webpacker.yml
/Users/xxxx/Desktop/rails_middle_tutorial/collabfield/config/environment.rb:5:in `<top (required)>'
/Users/xxxx/Desktop/rails_middle_tutorial/collabfield/bin/rails:9:in `<top (required)>'
/Users/xxxx/Desktop/rails_middle_tutorial/collabfield/bin/spring:15:in `require'
/Users/xxxx/Desktop/rails_middle_tutorial/collabfield/bin/spring:15:in `<top (required)>'
./bin/rails:3:in `load'
./bin/rails:3:in `<main>'

Caused by:
Errno::ENOENT: No such file or directory @ rb_sysopen - /Users/xxxx/Desktop/rails_middle_tutorial/collabfield/config/webpacker.yml
/Users/xxxx/Desktop/rails_middle_tutorial/collabfield/config/environment.rb:5:in `<top (required)>'
/Users/xxxx/Desktop/rails_middle_tutorial/collabfield/bin/rails:9:in `<top (required)>'
/Users/xxxx/Desktop/rails_middle_tutorial/collabfield/bin/spring:15:in `require'
/Users/xxxx/Desktop/rails_middle_tutorial/collabfield/bin/spring:15:in `<top (required)>'
./bin/rails:3:in `load'
./bin/rails:3:in `<main>'
Tasks: TOP => app:template => environment
(See full trace by running task with --trace)

Errno::ENOENT: No such file or directory @ rb_sysopen - /Users/xxxx/Desktop/rails_middle_tutorial/collabfield/config/webpacker.ymlとか出てるので調べてみるとwebpacker.ymlをconfig配下に手動で作るとか載っているのがありました。
早速試してみることに..

参考

webpacker.ymlを手動で作成したらその中に以下の参考サイトからコピペする。
https://raw.githubusercontent.com/rails/webpacker/master/lib/install/config/webpacker.yml

再度 rails webpacker:installを実行

ターミナル

xxxx-no-MacBook-Pro:collabfield xxxx$ rails webpacker:install
   identical  config/webpacker.yml
Copying webpack core config
      create  config/webpack
      create  config/webpack/development.js
      create  config/webpack/environment.js
      create  config/webpack/production.js
      create  config/webpack/test.js
Copying postcss.config.js to app root directory
      create  postcss.config.js
Copying babel.config.js to app root directory
      create  babel.config.js
Copying .browserslistrc to app root directory
      create  .browserslistrc
Creating JavaScript app source directory
      create  app/javascript
      create  app/javascript/packs/application.js
       apply  /Users/groovy/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/bundler/gems/webpacker-2cef2fd6c208/lib/install/binstubs.rb
  Copying binstubs
       exist    bin
      create    bin/webpack
      create    bin/webpack-dev-server
      append  .gitignore
Installing all JavaScript dependencies [4.0.7]
         run  yarn add @rails/webpacker from "."
yarn add v1.12.3
info No lockfile found.
[1/4] 🔍  Resolving packages...
warning @rails/webpacker > postcss-preset-env > postcss-color-functional-notation > postcss-values-parser > flatten@1.0.2: I wrote this module a very long time ago; you should use something else.
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
warning "@rails/webpacker > pnp-webpack-plugin > ts-pnp@1.1.4" has unmet peer dependency "typescript@*".
[4/4] 📃  Building fresh packages...
success Saved lockfile.
warning Your current version of Yarn is out of date. The latest version is "1.19.1", while you're on "1.12.3".
info To upgrade, run the following command:
$ curl --compressed -o- -L https://yarnpkg.com/install.sh | bash
success Saved 592 new dependencies.
info Direct dependencies
└─ @rails/webpacker@4.0.7
info All dependencies
├─ @babel/core@7.6.4
├─ @babel/generator@7.6.4
├─ @babel/helper-builder-binary-assignment-operator-visitor@7.1.0
├─ @babel/helper-call-delegate@7.4.4
├─ @babel/helper-create-class-features-plugin@7.6.0
├─ @babel/helper-define-map@7.5.5
├─ @babel/helper-explode-assignable-expression@7.1.0
├─ @babel/helper-wrap-function@7.2.0
├─ @babel/helpers@7.6.2
├─ @babel/highlight@7.5.0
├─ @babel/parser@7.6.4
├─ @babel/plugin-proposal-async-generator-functions@7.2.0
├─ @babel/plugin-proposal-class-properties@7.5.5
├─ @babel/plugin-proposal-dynamic-import@7.5.0
├─ @babel/plugin-proposal-json-strings@7.2.0
├─ @babel/plugin-proposal-object-rest-spread@7.6.2
├─ @babel/plugin-proposal-optional-catch-binding@7.2.0
├─ @babel/plugin-proposal-unicode-property-regex@7.6.2
├─ @babel/plugin-transform-arrow-functions@7.2.0
├─ @babel/plugin-transform-async-to-generator@7.5.0
├─ @babel/plugin-transform-block-scoped-functions@7.2.0
├─ @babel/plugin-transform-block-scoping@7.6.3
├─ @babel/plugin-transform-classes@7.5.5
├─ @babel/plugin-transform-computed-properties@7.2.0
├─ @babel/plugin-transform-destructuring@7.6.0
├─ @babel/plugin-transform-dotall-regex@7.6.2
├─ @babel/plugin-transform-duplicate-keys@7.5.0
├─ @babel/plugin-transform-exponentiation-operator@7.2.0
├─ @babel/plugin-transform-for-of@7.4.4
├─ @babel/plugin-transform-function-name@7.4.4
├─ @babel/plugin-transform-literals@7.2.0
├─ @babel/plugin-transform-member-expression-literals@7.2.0
├─ @babel/plugin-transform-modules-amd@7.5.0
├─ @babel/plugin-transform-modules-commonjs@7.6.0
├─ @babel/plugin-transform-modules-systemjs@7.5.0
├─ @babel/plugin-transform-modules-umd@7.2.0
├─ @babel/plugin-transform-named-capturing-groups-regex@7.6.3
├─ @babel/plugin-transform-new-target@7.4.4
├─ @babel/plugin-transform-object-super@7.5.5
├─ @babel/plugin-transform-parameters@7.4.4
├─ @babel/plugin-transform-property-literals@7.2.0
├─ @babel/plugin-transform-reserved-words@7.2.0
├─ @babel/plugin-transform-runtime@7.6.2
├─ @babel/plugin-transform-shorthand-properties@7.2.0
├─ @babel/plugin-transform-spread@7.6.2
├─ @babel/plugin-transform-sticky-regex@7.2.0
├─ @babel/plugin-transform-template-literals@7.4.4
├─ @babel/plugin-transform-typeof-symbol@7.2.0
├─ @babel/plugin-transform-unicode-regex@7.6.2
├─ @babel/preset-env@7.6.3
├─ @babel/runtime@7.6.3
├─ @babel/types@7.6.3
├─ @rails/webpacker@4.0.7
├─ @types/q@1.5.2
├─ @webassemblyjs/floating-point-hex-parser@1.8.5
├─ @webassemblyjs/helper-code-frame@1.8.5
├─ @webassemblyjs/helper-fsm@1.8.5
├─ @webassemblyjs/helper-wasm-section@1.8.5
├─ @webassemblyjs/wasm-edit@1.8.5
├─ @webassemblyjs/wasm-opt@1.8.5
├─ @xtuc/ieee754@1.2.0
├─ abbrev@1.1.1
├─ acorn@6.3.0
├─ ajv-errors@1.0.1
├─ ajv-keywords@3.4.1
├─ ajv@6.10.2
├─ amdefine@1.0.1
├─ ansi-styles@3.2.1
├─ anymatch@2.0.0
├─ are-we-there-yet@1.1.5
├─ argparse@1.0.10
├─ arr-flatten@1.1.0
├─ array-find-index@1.0.2
├─ asn1.js@4.10.1
├─ asn1@0.2.4
├─ assert@1.5.0
├─ assign-symbols@1.0.0
├─ async-each@1.0.3
├─ async-foreach@0.1.3
├─ asynckit@0.4.0
├─ atob@2.1.2
├─ autoprefixer@9.6.4
├─ aws-sign2@0.7.0
├─ aws4@1.8.0
├─ babel-loader@8.0.6
├─ babel-plugin-macros@2.6.1
├─ base@0.11.2
├─ base64-js@1.3.1
├─ bcrypt-pbkdf@1.0.2
├─ big.js@5.2.2
├─ binary-extensions@1.13.1
├─ block-stream@0.0.9
├─ boolbase@1.0.0
├─ brace-expansion@1.1.11
├─ braces@2.3.2
├─ browserify-aes@1.2.0
├─ browserify-cipher@1.0.1
├─ browserify-des@1.0.2
├─ browserify-sign@4.0.4
├─ browserify-zlib@0.2.0
├─ buffer-xor@1.0.3
├─ buffer@4.9.1
├─ builtin-status-codes@3.0.0
├─ cacache@11.3.3
├─ cache-base@1.0.1
├─ caller-callsite@2.0.0
├─ caller-path@2.0.0
├─ callsites@2.0.0
├─ camelcase-keys@2.1.0
├─ caniuse-lite@1.0.30000999
├─ case-sensitive-paths-webpack-plugin@2.2.0
├─ caseless@0.12.0
├─ chokidar@2.1.8
├─ chownr@1.1.3
├─ chrome-trace-event@1.0.2
├─ cipher-base@1.0.4
├─ class-utils@0.3.6
├─ cliui@5.0.0
├─ clone-deep@4.0.1
├─ coa@2.0.2
├─ code-point-at@1.1.0
├─ collection-visit@1.0.0
├─ color-convert@1.9.3
├─ color-name@1.1.3
├─ color-string@1.5.3
├─ color@3.1.2
├─ combined-stream@1.0.8
├─ commander@2.20.3
├─ commondir@1.0.1
├─ compression-webpack-plugin@2.0.0
├─ concat-map@0.0.1
├─ concat-stream@1.6.2
├─ console-browserify@1.1.0
├─ console-control-strings@1.1.0
├─ constants-browserify@1.0.0
├─ convert-source-map@1.6.0
├─ copy-concurrently@1.0.5
├─ copy-descriptor@0.1.1
├─ core-js-compat@3.2.1
├─ core-js@3.2.1
├─ core-util-is@1.0.2
├─ create-ecdh@4.0.3
├─ create-hmac@1.1.7
├─ cross-spawn@6.0.5
├─ crypto-browserify@3.12.0
├─ css-blank-pseudo@0.1.4
├─ css-color-names@0.0.4
├─ css-declaration-sorter@4.0.1
├─ css-has-pseudo@0.10.0
├─ css-loader@2.1.1
├─ css-prefers-color-scheme@3.1.1
├─ css-select-base-adapter@0.1.1
├─ css-select@2.0.2
├─ css-tree@1.0.0-alpha.33
├─ css-unit-converter@1.1.1
├─ css-what@2.1.3
├─ cssdb@4.4.0
├─ cssesc@2.0.0
├─ cssnano-preset-default@4.0.7
├─ cssnano-util-raw-cache@4.0.1
├─ cssnano-util-same-parent@4.0.1
├─ cssnano@4.1.10
├─ csso@3.5.1
├─ currently-unhandled@0.4.1
├─ cyclist@1.0.1
├─ dashdash@1.14.1
├─ date-now@0.1.4
├─ debug@2.6.9
├─ decamelize@1.2.0
├─ decode-uri-component@0.2.0
├─ deep-extend@0.6.0
├─ delayed-stream@1.0.0
├─ delegates@1.0.0
├─ des.js@1.0.0
├─ detect-file@1.0.0
├─ detect-libc@1.0.3
├─ diffie-hellman@5.0.3
├─ dom-serializer@0.2.1
├─ domain-browser@1.2.0
├─ domelementtype@1.3.1
├─ domutils@1.7.0
├─ dot-prop@4.2.0
├─ duplexify@3.7.1
├─ ecc-jsbn@0.1.2
├─ electron-to-chromium@1.3.280
├─ emoji-regex@7.0.3
├─ emojis-list@2.1.0
├─ enhanced-resolve@4.1.0
├─ entities@2.0.0
├─ error-ex@1.3.2
├─ es-abstract@1.15.0
├─ es-to-primitive@1.2.0
├─ escape-string-regexp@1.0.5
├─ eslint-scope@4.0.3
├─ esprima@4.0.1
├─ esrecurse@4.2.1
├─ estraverse@4.3.0
├─ events@3.0.0
├─ execa@1.0.0
├─ expand-brackets@2.1.4
├─ expand-tilde@2.0.2
├─ extend@3.0.2
├─ extglob@2.0.4
├─ extsprintf@1.3.0
├─ fast-deep-equal@2.0.1
├─ fast-json-stable-stringify@2.0.0
├─ file-loader@3.0.1
├─ fill-range@4.0.0
├─ find-cache-dir@2.1.0
├─ findup-sync@3.0.0
├─ flatted@2.0.1
├─ flatten@1.0.2
├─ flush-write-stream@1.1.1
├─ for-in@1.0.2
├─ forever-agent@0.6.1
├─ form-data@2.3.3
├─ from2@2.3.0
├─ fs-minipass@1.2.7
├─ fs.realpath@1.0.0
├─ fsevents@1.2.9
├─ fstream@1.0.12
├─ gauge@2.7.4
├─ gaze@1.1.3
├─ get-caller-file@2.0.5
├─ get-stream@4.1.0
├─ getpass@0.1.7
├─ glob-parent@3.1.0
├─ glob@7.1.4
├─ global-modules@2.0.0
├─ global-prefix@3.0.0
├─ globule@1.2.1
├─ har-schema@2.0.0
├─ har-validator@5.1.3
├─ has-ansi@2.0.0
├─ has-unicode@2.0.1
├─ has-value@1.0.0
├─ has-values@1.0.0
├─ has@1.0.3
├─ hash.js@1.1.7
├─ hex-color-regex@1.1.0
├─ hmac-drbg@1.0.1
├─ hosted-git-info@2.8.5
├─ hsl-regex@1.0.0
├─ hsla-regex@1.0.0
├─ html-comment-regex@1.1.2
├─ http-signature@1.2.0
├─ https-browserify@1.0.0
├─ iconv-lite@0.4.24
├─ icss-replace-symbols@1.1.0
├─ icss-utils@4.1.1
├─ ieee754@1.1.13
├─ ignore-walk@3.0.3
├─ import-cwd@2.1.0
├─ import-fresh@2.0.0
├─ import-from@2.1.0
├─ import-local@2.0.0
├─ in-publish@2.0.0
├─ indent-string@2.1.0
├─ infer-owner@1.0.4
├─ inflight@1.0.6
├─ ini@1.3.5
├─ interpret@1.2.0
├─ invariant@2.2.4
├─ invert-kv@2.0.0
├─ is-absolute-url@2.1.0
├─ is-accessor-descriptor@1.0.0
├─ is-arrayish@0.2.1
├─ is-binary-path@1.0.1
├─ is-color-stop@1.1.0
├─ is-data-descriptor@1.0.0
├─ is-date-object@1.0.1
├─ is-descriptor@1.0.2
├─ is-directory@0.3.1
├─ is-extglob@2.1.1
├─ is-finite@1.0.2
├─ is-obj@1.0.1
├─ is-plain-obj@1.1.0
├─ is-plain-object@2.0.4
├─ is-regex@1.0.4
├─ is-resolvable@1.1.0
├─ is-stream@1.1.0
├─ is-svg@3.0.0
├─ is-symbol@1.0.2
├─ is-typedarray@1.0.0
├─ is-utf8@0.2.1
├─ is-windows@1.0.2
├─ is-wsl@1.1.0
├─ isarray@1.0.0
├─ isexe@2.0.0
├─ isstream@0.1.2
├─ js-base64@2.5.1
├─ js-levenshtein@1.1.6
├─ js-tokens@4.0.0
├─ jsesc@2.5.2
├─ json-parse-better-errors@1.0.2
├─ json-schema-traverse@0.4.1
├─ json-schema@0.2.3
├─ json-stringify-safe@5.0.1
├─ json5@2.1.1
├─ jsprim@1.4.1
├─ last-call-webpack-plugin@3.0.0
├─ lcid@2.0.0
├─ load-json-file@1.1.0
├─ loader-runner@2.4.0
├─ locate-path@3.0.0
├─ lodash.get@4.4.2
├─ lodash.has@4.5.2
├─ lodash.memoize@4.1.2
├─ lodash.template@4.5.0
├─ lodash.templatesettings@4.2.0
├─ lodash.uniq@4.5.0
├─ lodash@4.17.15
├─ loose-envify@1.4.0
├─ loud-rejection@1.6.0
├─ make-dir@2.1.0
├─ mamacro@0.0.3
├─ map-age-cleaner@0.1.3
├─ map-obj@1.0.1
├─ map-visit@1.0.0
├─ mdn-data@2.0.4
├─ mem@4.3.0
├─ memory-fs@0.4.1
├─ meow@3.7.0
├─ miller-rabin@4.0.1
├─ mime-db@1.40.0
├─ mime-types@2.1.24
├─ mimic-fn@2.1.0
├─ mini-css-extract-plugin@0.7.0
├─ minimalistic-crypto-utils@1.0.1
├─ minimatch@3.0.4
├─ minimist@1.2.0
├─ minipass@2.9.0
├─ minizlib@1.3.3
├─ mixin-deep@1.3.2
├─ mkdirp@0.5.1
├─ ms@2.1.2
├─ nan@2.14.0
├─ nanomatch@1.2.13
├─ needle@2.4.0
├─ nice-try@1.0.5
├─ node-gyp@3.8.0
├─ node-libs-browser@2.2.1
├─ node-pre-gyp@0.12.0
├─ node-releases@1.1.35
├─ node-sass@4.12.0
├─ nopt@3.0.6
├─ normalize-package-data@2.5.0
├─ normalize-range@0.1.2
├─ normalize-url@1.9.1
├─ npm-bundled@1.0.6
├─ npm-packlist@1.4.6
├─ npm-run-path@2.0.2
├─ npmlog@4.1.2
├─ nth-check@1.0.2
├─ num2fraction@1.2.2
├─ oauth-sign@0.9.0
├─ object-assign@4.1.1
├─ object-copy@0.1.0
├─ object-inspect@1.6.0
├─ object-keys@1.1.1
├─ object.assign@4.1.0
├─ object.getownpropertydescriptors@2.0.3
├─ object.values@1.1.0
├─ optimize-css-assets-webpack-plugin@5.0.3
├─ os-browserify@0.3.0
├─ os-homedir@1.0.2
├─ os-locale@3.1.0
├─ os-tmpdir@1.0.2
├─ osenv@0.1.5
├─ p-defer@1.0.0
├─ p-finally@1.0.0
├─ p-is-promise@2.1.0
├─ p-limit@2.2.1
├─ p-locate@3.0.0
├─ p-try@2.2.0
├─ pako@1.0.10
├─ parallel-transform@1.2.0
├─ parse-json@4.0.0
├─ parse-passwd@1.0.0
├─ pascalcase@0.1.1
├─ path-browserify@0.0.1
├─ path-complete-extname@1.0.0
├─ path-dirname@1.0.2
├─ path-exists@3.0.0
├─ path-key@2.0.1
├─ path-parse@1.0.6
├─ path-type@1.1.0
├─ performance-now@2.1.0
├─ pinkie@2.0.4
├─ pnp-webpack-plugin@1.5.0
├─ posix-character-classes@0.1.1
├─ postcss-attribute-case-insensitive@4.0.1
├─ postcss-calc@7.0.1
├─ postcss-color-functional-notation@2.0.1
├─ postcss-color-gray@5.0.0
├─ postcss-color-hex-alpha@5.0.3
├─ postcss-color-mod-function@3.0.3
├─ postcss-color-rebeccapurple@4.0.1
├─ postcss-colormin@4.0.3
├─ postcss-convert-values@4.0.1
├─ postcss-custom-media@7.0.8
├─ postcss-custom-properties@8.0.11
├─ postcss-custom-selectors@5.1.2
├─ postcss-dir-pseudo-class@5.0.0
├─ postcss-discard-comments@4.0.2
├─ postcss-discard-duplicates@4.0.2
├─ postcss-discard-empty@4.0.1
├─ postcss-discard-overridden@4.0.1
├─ postcss-double-position-gradients@1.0.0
├─ postcss-env-function@2.0.2
├─ postcss-flexbugs-fixes@4.1.0
├─ postcss-focus-visible@4.0.0
├─ postcss-focus-within@3.0.0
├─ postcss-font-variant@4.0.0
├─ postcss-gap-properties@2.0.0
├─ postcss-image-set-function@3.0.1
├─ postcss-import@12.0.1
├─ postcss-initial@3.0.1
├─ postcss-lab-function@2.0.1
├─ postcss-load-config@2.1.0
├─ postcss-loader@3.0.0
├─ postcss-logical@3.0.0
├─ postcss-media-minmax@4.0.0
├─ postcss-merge-longhand@4.0.11
├─ postcss-merge-rules@4.0.3
├─ postcss-minify-font-values@4.0.2
├─ postcss-minify-gradients@4.0.2
├─ postcss-minify-params@4.0.2
├─ postcss-minify-selectors@4.0.2
├─ postcss-modules-extract-imports@2.0.0
├─ postcss-modules-local-by-default@2.0.6
├─ postcss-modules-scope@2.1.0
├─ postcss-modules-values@2.0.0
├─ postcss-nesting@7.0.1
├─ postcss-normalize-charset@4.0.1
├─ postcss-normalize-display-values@4.0.2
├─ postcss-normalize-positions@4.0.2
├─ postcss-normalize-repeat-style@4.0.2
├─ postcss-normalize-string@4.0.2
├─ postcss-normalize-timing-functions@4.0.2
├─ postcss-normalize-unicode@4.0.1
├─ postcss-normalize-url@4.0.1
├─ postcss-normalize-whitespace@4.0.2
├─ postcss-ordered-values@4.1.2
├─ postcss-overflow-shorthand@2.0.0
├─ postcss-page-break@2.0.0
├─ postcss-place@4.0.1
├─ postcss-preset-env@6.7.0
├─ postcss-pseudo-class-any-link@6.0.0
├─ postcss-reduce-initial@4.0.3
├─ postcss-reduce-transforms@4.0.2
├─ postcss-replace-overflow-wrap@3.0.0
├─ postcss-safe-parser@4.0.1
├─ postcss-selector-matches@4.0.0
├─ postcss-selector-not@4.0.0
├─ postcss-svgo@4.0.2
├─ postcss-unique-selectors@4.0.1
├─ prepend-http@1.0.4
├─ private@0.1.8
├─ process-nextick-args@2.0.1
├─ process@0.11.10
├─ prr@1.0.1
├─ pseudomap@1.0.2
├─ psl@1.4.0
├─ public-encrypt@4.0.3
├─ pumpify@1.5.1
├─ punycode@1.4.1
├─ q@1.5.1
├─ qs@6.5.2
├─ query-string@4.3.4
├─ querystring-es3@0.2.1
├─ querystring@0.2.0
├─ randomfill@1.0.4
├─ rc@1.2.8
├─ read-cache@1.0.0
├─ read-pkg@1.1.0
├─ readdirp@2.2.1
├─ redent@1.0.0
├─ regenerate-unicode-properties@8.1.0
├─ regenerator-transform@0.14.1
├─ regjsgen@0.5.0
├─ regjsparser@0.6.0
├─ remove-trailing-separator@1.1.0
├─ repeat-element@1.1.3
├─ repeating@2.0.1
├─ request@2.88.0
├─ require-main-filename@2.0.0
├─ resolve-cwd@2.0.0
├─ resolve-dir@1.0.1
├─ resolve-url@0.2.1
├─ ret@0.1.15
├─ rgb-regex@1.0.1
├─ rgba-regex@1.0.0
├─ rimraf@2.7.1
├─ run-queue@1.0.3
├─ safer-buffer@2.1.2
├─ sass-graph@2.2.4
├─ sass-loader@7.3.1
├─ sax@1.2.4
├─ scss-tokenizer@0.2.3
├─ semver@5.7.1
├─ serialize-javascript@1.9.1
├─ set-value@2.0.1
├─ setimmediate@1.0.5
├─ shallow-clone@3.0.1
├─ shebang-command@1.2.0
├─ shebang-regex@1.0.0
├─ simple-swizzle@0.2.2
├─ snapdragon-node@2.1.1
├─ snapdragon-util@3.0.1
├─ sort-keys@1.1.2
├─ source-list-map@2.0.1
├─ source-map-resolve@0.5.2
├─ source-map-support@0.5.13
├─ source-map-url@0.4.0
├─ spdx-correct@3.1.0
├─ spdx-exceptions@2.2.0
├─ split-string@3.1.0
├─ sprintf-js@1.0.3
├─ sshpk@1.16.1
├─ stable@0.1.8
├─ static-extend@0.1.2
├─ stdout-stream@1.4.1
├─ stream-browserify@2.0.2
├─ stream-each@1.2.3
├─ stream-http@2.8.3
├─ strict-uri-encode@1.1.0
├─ string_decoder@1.1.1
├─ string.prototype.trimleft@2.1.0
├─ string.prototype.trimright@2.1.0
├─ strip-bom@2.0.0
├─ strip-eof@1.0.0
├─ strip-indent@1.0.1
├─ strip-json-comments@2.0.1
├─ style-loader@0.23.1
├─ stylehacks@4.0.3
├─ supports-color@6.1.0
├─ svgo@1.3.0
├─ tar@2.2.2
├─ terser-webpack-plugin@1.4.1
├─ terser@4.3.8
├─ through2@2.0.5
├─ timers-browserify@2.0.11
├─ timsort@0.3.0
├─ to-arraybuffer@1.0.1
├─ to-fast-properties@2.0.0
├─ to-object-path@0.3.0
├─ to-regex-range@2.1.1
├─ tough-cookie@2.4.3
├─ trim-newlines@1.0.0
├─ true-case-path@1.0.3
├─ ts-pnp@1.1.4
├─ tslib@1.10.0
├─ tty-browserify@0.0.0
├─ tunnel-agent@0.6.0
├─ tweetnacl@0.14.5
├─ typedarray@0.0.6
├─ unicode-canonical-property-names-ecmascript@1.0.4
├─ unicode-match-property-ecmascript@1.0.4
├─ unicode-match-property-value-ecmascript@1.1.0
├─ unicode-property-aliases-ecmascript@1.0.5
├─ union-value@1.0.1
├─ unique-slug@2.0.2
├─ unquote@1.1.1
├─ unset-value@1.0.0
├─ upath@1.2.0
├─ uri-js@4.2.2
├─ urix@0.1.0
├─ url@0.11.0
├─ use@3.1.1
├─ util-deprecate@1.0.2
├─ util.promisify@1.0.0
├─ util@0.11.1
├─ uuid@3.3.3
├─ v8-compile-cache@2.0.3
├─ validate-npm-package-license@3.0.4
├─ vendors@1.0.3
├─ verror@1.10.0
├─ vm-browserify@1.1.0
├─ watchpack@1.6.0
├─ webpack-assets-manifest@3.1.1
├─ webpack-cli@3.3.9
├─ webpack@4.41.0
├─ which-module@2.0.0
├─ which@1.3.1
├─ wide-align@1.1.3
├─ worker-farm@1.7.0
├─ wrap-ansi@5.1.0
├─ xtend@4.0.2
├─ yallist@3.1.1
├─ yargs-parser@13.1.1
└─ yargs@13.2.4
✨  Done in 24.18s.
Installing dev server for live reloading
         run  yarn add --dev webpack-dev-server from "."
yarn add v1.12.3
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
warning "@rails/webpacker > pnp-webpack-plugin > ts-pnp@1.1.4" has unmet peer dependency "typescript@*".
warning "webpack-dev-server > webpack-dev-middleware@3.7.2" has unmet peer dependency "webpack@^4.0.0".
warning " > webpack-dev-server@3.8.2" has unmet peer dependency "webpack@^4.0.0".
[4/4] 📃  Building fresh packages...
success Saved lockfile.
success Saved 101 new dependencies.
info Direct dependencies
└─ webpack-dev-server@3.8.2
info All dependencies
├─ @types/events@3.0.0
├─ @types/glob@7.1.1
├─ @types/minimatch@3.0.3
├─ @types/node@12.7.12
├─ accepts@1.3.7
├─ ansi-colors@3.2.4
├─ ansi-html@0.0.7
├─ array-flatten@1.1.1
├─ array-union@1.0.2
├─ array-uniq@1.0.3
├─ async-limiter@1.0.1
├─ async@1.5.2
├─ batch@0.6.1
├─ body-parser@1.19.0
├─ bonjour@3.5.0
├─ buffer-indexof@1.1.1
├─ cliui@4.1.0
├─ compressible@2.0.17
├─ compression@1.7.4
├─ connect-history-api-fallback@1.6.0
├─ content-disposition@0.5.3
├─ cookie-signature@1.0.6
├─ cookie@0.4.0
├─ deep-equal@1.1.0
├─ default-gateway@4.2.0
├─ del@4.1.1
├─ destroy@1.0.4
├─ detect-node@2.0.4
├─ dns-equal@1.0.0
├─ dns-packet@1.3.1
├─ dns-txt@2.0.2
├─ ee-first@1.1.1
├─ eventemitter3@4.0.0
├─ eventsource@1.0.7
├─ express@4.17.1
├─ faye-websocket@0.10.0
├─ finalhandler@1.1.2
├─ follow-redirects@1.9.0
├─ forwarded@0.1.2
├─ globby@6.1.0
├─ handle-thing@2.0.0
├─ hpack.js@2.1.6
├─ html-entities@1.2.1
├─ http-deceiver@1.2.7
├─ http-parser-js@0.4.10
├─ http-proxy-middleware@0.19.1
├─ http-proxy@1.18.0
├─ internal-ip@4.3.0
├─ ip-regex@2.1.0
├─ ip@1.1.5
├─ ipaddr.js@1.9.1
├─ is-absolute-url@3.0.3
├─ is-arguments@1.0.4
├─ is-path-cwd@2.2.0
├─ is-path-in-cwd@2.1.0
├─ is-path-inside@2.1.0
├─ json3@3.3.3
├─ killable@1.0.1
├─ loglevel@1.6.4
├─ media-typer@0.3.0
├─ merge-descriptors@1.0.1
├─ methods@1.1.2
├─ mime@2.4.4
├─ multicast-dns-service-types@1.1.0
├─ multicast-dns@6.2.3
├─ negotiator@0.6.2
├─ node-forge@0.9.0
├─ object-is@1.0.1
├─ obuf@1.1.2
├─ on-headers@1.0.2
├─ opn@5.5.0
├─ original@1.0.2
├─ p-map@2.1.0
├─ p-retry@3.0.1
├─ path-is-inside@1.0.2
├─ path-to-regexp@0.1.7
├─ portfinder@1.0.24
├─ proxy-addr@2.0.5
├─ querystringify@2.1.1
├─ raw-body@2.4.0
├─ regexp.prototype.flags@1.2.0
├─ retry@0.12.0
├─ select-hose@2.0.0
├─ selfsigned@1.10.7
├─ serve-index@1.9.1
├─ serve-static@1.14.1
├─ sockjs-client@1.4.0
├─ sockjs@0.3.19
├─ spdy-transport@3.0.0
├─ spdy@4.0.1
├─ thunky@1.0.3
├─ type-is@1.6.18
├─ unpipe@1.0.0
├─ utils-merge@1.0.1
├─ wbuf@1.7.3
├─ webpack-dev-middleware@3.7.2
├─ webpack-dev-server@3.8.2
├─ websocket-extensions@0.1.3
├─ ws@6.2.1
├─ yargs-parser@11.1.1
└─ yargs@12.0.5
✨  Done in 8.46s.
You need to allow webpack-dev-server host as allowed origin for connect-src.
This can be done in Rails 5.2+ for development environment in the CSP initializer
config/initializers/content_security_policy.rb with a snippet like this:
policy.connect_src :self, :https, "http://localhost:3035", "ws://localhost:3035" if Rails.env.development?
Webpacker successfully installed 🎉 🍰

うまくいったようです。
でも何が原因だったかわかりません。
どなたか教えてくださいませー。