Run vale linter only if vale is installed

scripts/check-docs-quality.js

@@ -16,6 +16,8 @@
  */
 const { execSync, spawnSync } = require('child_process');
 const path = require('path');
+// eslint-disable-next-line import/no-extraneous-dependencies
+const commandExists = require('command-exists');
 
 const listFilesTrackedByGit = 'git ls-files';
 
@@ -23,46 +25,58 @@ const inheritStdIo = {
   stdio: 'inherit',
 };
 
+const LINT_SKIPPED_MESSAGE =
+  'Skipping documentation quality check (vale not found). Install vale linter (https://docs.errata.ai/vale/install) to enable.\n';
 const ERROR_MESSAGE =
-  'Please install vale linter(https://docs.errata.ai/vale/install). Ignore this message if already installed.\n';
+  'Language linter (vale) generated errors. Please check the errors and review any markdown files that you changed.\n';
 
-// xargs is not supported by shx.
-if (process.platform === 'win32') {
-  const validMDFilesCommand = `${listFilesTrackedByGit} | .\\node_modules\\.bin\\shx grep ".md"`;
-  try {
-    // get list of all md files except in directories of gitignore.
-    let filesToLint = execSync(validMDFilesCommand, {
-      stdio: ['ignore', 'pipe', 'inherit'],
-    });
+// Proceed with the script only if Vale linter is installed. Limit the friction and surprises caused by the script.
+commandExists('vale')
+  .catch(() => {
+    console.log(LINT_SKIPPED_MESSAGE);
+    process.exit(0);
+  })
+  .then(() => {
+    // xargs is not supported by shx.
+    if (process.platform === 'win32') {
+      const validMDFilesCommand = `${listFilesTrackedByGit} | .\\node_modules\\.bin\\shx grep ".md"`;
+      try {
+        // get list of all md files except in directories of gitignore.
+        let filesToLint = execSync(validMDFilesCommand, {
+          stdio: ['ignore', 'pipe', 'inherit'],
+        });
 
-    // set all file(s) path as absolute path
-    filesToLint = filesToLint
-      .toString()
-      .split('\n')
-      .map(filepath => (filepath ? path.join(process.cwd(), filepath) : null))
-      .filter(Boolean);
+        // set all file(s) path as absolute path
+        filesToLint = filesToLint
+          .toString()
+          .split('\n')
+          .map(filepath =>
+            filepath ? path.join(process.cwd(), filepath) : null,
+          )
+          .filter(Boolean);
 
-    const output = spawnSync('vale', filesToLint, inheritStdIo);
+        const output = spawnSync('vale', filesToLint, inheritStdIo);
 
-    // if the command does not succeed
-    if (output.status !== 0) {
-      // if it contains system level error. [in this case vale does not exist]
-      if (output.error) {
-        console.error(ERROR_MESSAGE);
+        // if the command does not succeed
+        if (output.status !== 0) {
+          // if it contains system level error. [in this case vale does not exist]
+          if (output.error) {
+            console.error(ERROR_MESSAGE);
+          }
+          process.exit(1);
+        }
+      } catch (e) {
+        console.error(e.message);
+        process.exit(1);
+      }
+    } else {
+      const validMDFilesCommand = `${listFilesTrackedByGit} | ./node_modules/.bin/shx grep ".md"`;
+      // use xargs
+      try {
+        execSync(`${validMDFilesCommand} | xargs vale`, inheritStdIo);
+      } catch (e) {
+        console.error(ERROR_MESSAGE);
+        process.exit(1);
       }
-      process.exit(1);
     }
-  } catch (e) {
-    console.error(e.message);
-    process.exit(1);
-  }
-} else {
-  const validMDFilesCommand = `${listFilesTrackedByGit} | ./node_modules/.bin/shx grep ".md"`;
-  // use xargs
-  try {
-    execSync(`${validMDFilesCommand} | xargs vale`, inheritStdIo);
-  } catch (e) {
-    console.error(ERROR_MESSAGE);
-    process.exit(1);
-  }
-}
+  });