fix(#337): wrap require prettier in a try-catch so that we don't thro…

…w when dep tree has no prettier

lib/rules/decorator-position.js

@@ -309,9 +309,16 @@ function configuredDecoratorsInOptions(options) {
 
 function lineLength(userOptions, filePath) {
   if (!prettier) {
-    // we acknowledge that this might not exist
-    // eslint-disable-next-line node/no-unpublished-require
-    prettier = require('prettier');
+    try {
+      // we acknowledge that this might not exist
+      // eslint-disable-next-line node/no-unpublished-require
+      prettier = require('prettier');
+    } catch (error) {
+      // throw an all errors that aren't "Cannot find module"
+      if (!error.message.includes('Cannot find module')) {
+        throw error;
+      }
+    }
   }
 
   const eslintPrettierRules = cli.getConfigForFile(filePath).rules['prettier/prettier'] || [];
@@ -323,17 +330,18 @@ function lineLength(userOptions, filePath) {
 
   const eslintPrettierOptions = eslintPrettierRules[1] || {};
   const usePrettierrc = !eslintPrettierOptions || eslintPrettierOptions.usePrettierrc !== false;
-  const prettierRcOptions = usePrettierrc
-    ? prettier.resolveConfig.sync(filePath, {
-        editorconfig: true,
-      })
-    : {};
+  const prettierRcOptions =
+    prettier && usePrettierrc
+      ? prettier.resolveConfig.sync(filePath, {
+          editorconfig: true,
+        })
+      : {};
 
   const prettierOptions = Object.assign({}, prettierRcOptions, eslintPrettierOptions, {
     filePath,
   });
 
-  if (!('printWidth' in prettierOptions)) {
+  if (prettier && !('printWidth' in prettierOptions)) {
     // available at prettier/src/main/core-options
     // keep an eye on this. There may have been an issue with prettier 2.2.0
     // but I've been unable to get the tests to pass prior to this change with *any*