EarthmanMuons · elasticdog · Jul 27, 2026 · Jul 27, 2026
diff --git a/.github/workflows/bump-version-flutter-app.yml b/.github/workflows/bump-version-flutter-app.yml
@@ -15,6 +15,13 @@ on:
         required: false
         type: string
         default: ""
+      prettier_plugins:
+        description: >
+          Optional whitespace-delimited list of npm package specs to install so that
+          Prettier can resolve the plugins named by the project's configuration.
+        required: false
+        type: string
+        default: ""
     secrets:
       APP_ID:
         description: GitHub App installation ID
@@ -78,7 +85,35 @@ jobs:
         run: get-project-version | bump-changelog-version
 
       - name: Fix up CHANGELOG formatting
-        run: npx --yes prettier@latest --color --prose-wrap always --write -- **/CHANGELOG.md
+        env:
+          INPUTS_PRETTIER_PLUGINS: ${{ inputs.prettier_plugins }}
+        # zizmor: ignore[adhoc-packages] This reusable workflow intentionally installs caller-selected Prettier packages on ephemeral runners.
+        run: |
+          set -euo pipefail
+
+          if [[ -n "${INPUTS_PRETTIER_PLUGINS}" ]]; then
+            # Plugins named by the project's Prettier config must be resolvable
+            # from the checkout, so install them alongside Prettier itself.
+            IFS=' ' read -r -a plugins <<<"$INPUTS_PRETTIER_PLUGINS"
+
+            # Keep the installed packages out of the release pull request.
+            if [[ ! -e node_modules ]]; then
+              trap 'rm -rf node_modules' EXIT
+            fi
+
+            npm install \
+              --no-save \
+              --no-package-lock \
+              --ignore-scripts \
+              prettier@latest \
+              "${plugins[@]}"
+
+            prettier=(npx --no-install prettier)
+          else
+            prettier=(npx --yes prettier@latest)
+          fi
+
+          "${prettier[@]}" --color --prose-wrap always --write -- **/CHANGELOG.md
 
       - name: Rotate unreleased whatsnew docs into release directory
         run: get-project-version | rotate-whatsnew

diff --git a/.github/workflows/bump-version-flutter-lib.yml b/.github/workflows/bump-version-flutter-lib.yml
@@ -7,6 +7,13 @@ on:
         description: Bump level
         required: true
         type: string
+      prettier_plugins:
+        description: >
+          Optional whitespace-delimited list of npm package specs to install so that
+          Prettier can resolve the plugins named by the project's configuration.
+        required: false
+        type: string
+        default: ""
     secrets:
       APP_ID:
         description: GitHub App installation ID
@@ -81,7 +88,35 @@ jobs:
         run: get-project-version | bump-changelog-version
 
       - name: Fix up CHANGELOG formatting
-        run: npx --yes prettier@latest --color --prose-wrap always --write -- **/CHANGELOG.md
+        env:
+          INPUTS_PRETTIER_PLUGINS: ${{ inputs.prettier_plugins }}
+        # zizmor: ignore[adhoc-packages] This reusable workflow intentionally installs caller-selected Prettier packages on ephemeral runners.
+        run: |
+          set -euo pipefail
+
+          if [[ -n "${INPUTS_PRETTIER_PLUGINS}" ]]; then
+            # Plugins named by the project's Prettier config must be resolvable
+            # from the checkout, so install them alongside Prettier itself.
+            IFS=' ' read -r -a plugins <<<"$INPUTS_PRETTIER_PLUGINS"
+
+            # Keep the installed packages out of the release pull request.
+            if [[ ! -e node_modules ]]; then
+              trap 'rm -rf node_modules' EXIT
+            fi
+
+            npm install \
+              --no-save \
+              --no-package-lock \
+              --ignore-scripts \
+              prettier@latest \
+              "${plugins[@]}"
+
+            prettier=(npx --no-install prettier)
+          else
+            prettier=(npx --yes prettier@latest)
+          fi
+
+          "${prettier[@]}" --color --prose-wrap always --write -- **/CHANGELOG.md
 
       - name: Rotate unreleased whatsnew docs into release directory
         run: get-project-version | rotate-whatsnew

diff --git a/.github/workflows/bump-version-rust.yml b/.github/workflows/bump-version-rust.yml
@@ -12,6 +12,13 @@ on:
         description: Bump level
         required: true
         type: string
+      prettier_plugins:
+        description: >
+          Optional whitespace-delimited list of npm package specs to install so that
+          Prettier can resolve the plugins named by the project's configuration.
+        required: false
+        type: string
+        default: ""
     secrets:
       APP_ID:
         description: GitHub App installation ID
@@ -95,7 +102,35 @@ jobs:
         run: cargo release replace -v --execute --no-confirm --package "${INPUTS_PACKAGE}"
 
       - name: Fix up CHANGELOG formatting
-        run: npx --yes prettier@latest --color --prose-wrap always --write -- **/CHANGELOG.md
+        env:
+          INPUTS_PRETTIER_PLUGINS: ${{ inputs.prettier_plugins }}
+        # zizmor: ignore[adhoc-packages] This reusable workflow intentionally installs caller-selected Prettier packages on ephemeral runners.
+        run: |
+          set -euo pipefail
+
+          if [[ -n "${INPUTS_PRETTIER_PLUGINS}" ]]; then
+            # Plugins named by the project's Prettier config must be resolvable
+            # from the checkout, so install them alongside Prettier itself.
+            IFS=' ' read -r -a plugins <<<"$INPUTS_PRETTIER_PLUGINS"
+
+            # Keep the installed packages out of the release pull request.
+            if [[ ! -e node_modules ]]; then
+              trap 'rm -rf node_modules' EXIT
+            fi
+
+            npm install \
+              --no-save \
+              --no-package-lock \
+              --ignore-scripts \
+              prettier@latest \
+              "${plugins[@]}"
+
+            prettier=(npx --no-install prettier)
+          else
+            prettier=(npx --yes prettier@latest)
+          fi
+
+          "${prettier[@]}" --color --prose-wrap always --write -- **/CHANGELOG.md
 
       - id: version
         name: Get the new release version

diff --git a/.github/workflows/check-html.yml b/.github/workflows/check-html.yml
@@ -6,6 +6,9 @@ on:
       files:
         type: string
         default: "**/*.html"
+      prettier_plugins:
+        type: string
+        default: ""
       prettier_version:
         type: string
         default: "latest"
@@ -22,15 +25,34 @@ jobs:
 
       - name: Check HTML file formatting
         env:
+          INPUTS_PRETTIER_PLUGINS: ${{ inputs.prettier_plugins }}
           INPUTS_PRETTIER_VERSION: ${{ inputs.prettier_version }}
           INPUTS_FILES: ${{ inputs.files }}
+        # zizmor: ignore[adhoc-packages] This reusable workflow intentionally installs caller-selected Prettier packages on ephemeral runners.
         run: |
           set -euo pipefail
 
           # Split INPUTS_FILES into an array (space-separated)
           IFS=' ' read -r -a files <<<"$INPUTS_FILES"
 
-          npx --yes "prettier@${INPUTS_PRETTIER_VERSION}" \
+          if [[ -n "${INPUTS_PRETTIER_PLUGINS}" ]]; then
+            # Plugins named by the caller's Prettier config must be resolvable
+            # from the checkout, so install them alongside Prettier itself.
+            IFS=' ' read -r -a plugins <<<"$INPUTS_PRETTIER_PLUGINS"
+
+            npm install \
+              --no-save \
+              --no-package-lock \
+              --ignore-scripts \
+              "prettier@${INPUTS_PRETTIER_VERSION}" \
+              "${plugins[@]}"
+
+            prettier=(npx --no-install prettier)
+          else
+            prettier=(npx --yes "prettier@${INPUTS_PRETTIER_VERSION}")
+          fi
+
+          "${prettier[@]}" \
             --check \
             --debug-check \
             --color \

diff --git a/.github/workflows/check-markdown.yml b/.github/workflows/check-markdown.yml
@@ -6,6 +6,9 @@ on:
       files:
         type: string
         default: "**/*.md"
+      prettier_plugins:
+        type: string
+        default: ""
       prettier_version:
         type: string
         default: "latest"
@@ -22,15 +25,34 @@ jobs:
 
       - name: Check Markdown file formatting
         env:
+          INPUTS_PRETTIER_PLUGINS: ${{ inputs.prettier_plugins }}
           INPUTS_PRETTIER_VERSION: ${{ inputs.prettier_version }}
           INPUTS_FILES: ${{ inputs.files }}
+        # zizmor: ignore[adhoc-packages] This reusable workflow intentionally installs caller-selected Prettier packages on ephemeral runners.
         run: |
           set -euo pipefail
 
           # Split INPUTS_FILES into an array (space-separated)
           IFS=' ' read -r -a files <<<"$INPUTS_FILES"
 
-          npx --yes "prettier@${INPUTS_PRETTIER_VERSION}" \
+          if [[ -n "${INPUTS_PRETTIER_PLUGINS}" ]]; then
+            # Plugins named by the caller's Prettier config must be resolvable
+            # from the checkout, so install them alongside Prettier itself.
+            IFS=' ' read -r -a plugins <<<"$INPUTS_PRETTIER_PLUGINS"
+
+            npm install \
+              --no-save \
+              --no-package-lock \
+              --ignore-scripts \
+              "prettier@${INPUTS_PRETTIER_VERSION}" \
+              "${plugins[@]}"
+
+            prettier=(npx --no-install prettier)
+          else
+            prettier=(npx --yes "prettier@${INPUTS_PRETTIER_VERSION}")
+          fi
+
+          "${prettier[@]}" \
             --check \
             --debug-check \
             --color \

diff --git a/docs/common.md b/docs/common.md
@@ -12,6 +12,42 @@ jobs:
     uses: EarthmanMuons/reusable-workflows/.github/workflows/check-spelling.yml@main
 ```
 
+## Prettier Plugins
+
+Prettier loads the plugins named by a project's configuration at startup, before
+it looks at any file, and resolves them from the checkout root. A repository
+whose `.prettierrc` declares a plugin will therefore fail **every** Prettier job
+with an error like:
+
+```
+[error] Cannot find package 'prettier-plugin-astro' imported from /home/runner/work/PROJECT/PROJECT/noop.js
+```
+
+That happens regardless of which file types the job formats, so a Markdown-only
+check fails just as an HTML one does.
+
+Workflows that run Prettier accept a `prettier_plugins` input listing the npm
+packages to install into the checkout beforehand, so Prettier can resolve them.
+Entries are whitespace-delimited and may pin a version:
+
+```yml
+jobs:
+  check_markdown:
+    uses: EarthmanMuons/reusable-workflows/.github/workflows/check-markdown.yml@main
+    with:
+      prettier_plugins: prettier-plugin-astro
+```
+
+The packages are only installed, never enabled on the command line; the
+project's own Prettier configuration remains the source of truth for which
+plugins are active. Leaving the input empty preserves the default behavior of
+running Prettier with no additional packages.
+
+Applies to [check-html.yml](#check-htmlyml),
+[check-markdown.yml](#check-markdownyml), and the CHANGELOG formatting step in
+the `bump-version-*` workflows documented under [Flutter](flutter.md) and
+[Rust](rust.md).
+
 ---
 
 ## detect-changed-files.yml
@@ -124,8 +160,11 @@ Checks HTML formatting using [Prettier](https://prettier.io/).
 | Name               | Required | Default     |
 | ------------------ | -------- | ----------- |
 | `files`            | false    | `**/*.html` |
+| `prettier_plugins` | false    | `""`        |
 | `prettier_version` | false    | `latest`    |
 
+See [Prettier plugins](#prettier-plugins) for when `prettier_plugins` is needed.
+
 **Typical usage with changed files**
 
 ```yml
@@ -154,8 +193,11 @@ Checks Markdown formatting using [Prettier](https://prettier.io/).
 | Name               | Required | Default   |
 | ------------------ | -------- | --------- |
 | `files`            | false    | `**/*.md` |
+| `prettier_plugins` | false    | `""`      |
 | `prettier_version` | false    | `latest`  |
 
+See [Prettier plugins](#prettier-plugins) for when `prettier_plugins` is needed.
+
 ---
 
 ## check-python.yml

diff --git a/docs/flutter.md b/docs/flutter.md
@@ -58,10 +58,14 @@ preparation pull request.
 
 **Inputs**
 
-| Name            | Required | Default |
-| --------------- | -------- | ------- |
-| `date_override` | false    | `""`    |
-| `format`        | false    | `""`    |
+| Name               | Required | Default |
+| ------------------ | -------- | ------- |
+| `date_override`    | false    | `""`    |
+| `format`           | false    | `""`    |
+| `prettier_plugins` | false    | `""`    |
+
+`prettier_plugins` covers the CHANGELOG formatting step; see
+[Prettier plugins](common.md#prettier-plugins).
 
 **Secrets**
 
@@ -83,9 +87,13 @@ preparation pull request.
 
 **Inputs**
 
-| Name    | Required | Default |
-| ------- | -------- | ------- |
-| `level` | true     | —       |
+| Name               | Required | Default |
+| ------------------ | -------- | ------- |
+| `level`            | true     | —       |
+| `prettier_plugins` | false    | `""`    |
+
+`prettier_plugins` covers the CHANGELOG formatting step; see
+[Prettier plugins](common.md#prettier-plugins).
 
 **Secrets**
 

diff --git a/docs/rust.md b/docs/rust.md
@@ -61,13 +61,17 @@ versions, update documentation, and open a PR.
 
 **Inputs**
 
-| Name      | Required | Default |
-| --------- | -------- | ------- |
-| `package` | true     | —       |
-| `level`   | true     | —       |
+| Name               | Required | Default |
+| ------------------ | -------- | ------- |
+| `package`          | true     | —       |
+| `level`            | true     | —       |
+| `prettier_plugins` | false    | `""`    |
 
 `level` must be `major`, `minor`, `patch`, `release`, `rc`, `beta`, or `alpha`.
 
+`prettier_plugins` covers the CHANGELOG formatting step; see
+[Prettier plugins](common.md#prettier-plugins).
+
 **Secrets**
 
 - `APP_ID`