feat(cli): add `--loglevel` option (#2992)

* feat(cli): add `--loglevel` option

* fix: handle error from invalid option

* fix: choice value and shouldLog logic

* test: fix test cases

* fix: change log style

* test: truncate snapshots

* test: reduce duplicate code

* test: use patterns instead of snapshots

* test: fix regex

src/cli-constant.js

@@ -187,6 +187,12 @@ const detailedOptions = normalizeDetailedOptions({
     description:
       "Print the names of files that are different from Prettier's formatting."
   },
+  loglevel: {
+    type: "choice",
+    description: "What level of logs to report.",
+    default: "warn",
+    choices: ["silent", "error", "warn", "debug"]
+  },
   parser: {
     type: "choice",
     category: CATEGORY_FORMAT,
@@ -334,13 +340,7 @@ const minimistOptions = {
       (current, option) =>
         Object.assign({ [option.name]: option.alias }, current),
       {}
-    ),
+    )
-  unknown: param => {
-    if (param.startsWith("-")) {
-      console.warn(`Ignored unknown option: ${param}\n`);
-      return false;
-    }
-  }
 };
 
 const usageSummary = `

src/cli-logger.js

@@ -0,0 +1,48 @@
+"use strict";
+
+const ENV_LOG_LEVEL = "PRETTIER_LOG_LEVEL";
+
+const chalk = require("chalk");
+
+const warn = createLogger("warn", "yellow");
+const error = createLogger("error", "red");
+const debug = createLogger("debug", "blue");
+
+function createLogger(loggerName, color) {
+  const prefix = `[${chalk[color](loggerName)}] `;
+  return function(message) {
+    if (shouldLog(loggerName)) {
+      console.error(message.replace(/^/gm, prefix).replace(/[\t ]+$/gm, ""));
+    }
+  };
+}
+
+function shouldLog(loggerName) {
+  const logLevel = process.env[ENV_LOG_LEVEL];
+
+  switch (logLevel) {
+    case "silent":
+      return false;
+    default:
+      return true;
+    case "debug":
+      if (loggerName === "debug") {
+        return true;
+      }
+    // fall through
+    case "warn":
+      if (loggerName === "warn") {
+        return true;
+      }
+    // fall through
+    case "error":
+      return loggerName === "error";
+  }
+}
+
+module.exports = {
+  warn,
+  error,
+  debug,
+  ENV_LOG_LEVEL
+};

src/cli-util.js

@@ -18,6 +18,7 @@ const constant = require("./cli-constant");
 const validator = require("./cli-validator");
 const apiDefaultOptions = require("./options").defaults;
 const errors = require("./errors");
+const logger = require("./cli-logger");
 
 const OPTION_USAGE_THRESHOLD = 25;
 const CHOICE_USAGE_MARGIN = 3;
@@ -57,15 +58,15 @@ function handleError(filename, error) {
   // `util.inspect` of throws things that aren't `Error` objects. (The Flow
   // parser has mistakenly thrown arrays sometimes.)
   if (isParseError) {
-    console.error(`${filename}: ${String(error)}`);
+    logger.error(`${filename}: ${String(error)}`);
   } else if (isValidationError || error instanceof errors.ConfigError) {
-    console.error(String(error));
+    logger.error(String(error));
     // If validation fails for one file, it will fail for all of them.
     process.exit(1);
   } else if (error instanceof errors.DebugError) {
-    console.error(`${filename}: ${error.message}`);
+    logger.error(`${filename}: ${error.message}`);
   } else {
-    console.error(filename + ":", error.stack || error);
+    logger.error(filename + ": " + (error.stack || error));
   }
 
   // Don't exit the process if one file failed
@@ -146,25 +147,44 @@ function format(argv, input, opt) {
 
 function getOptionsOrDie(argv, filePath) {
   try {
-    return argv["config"] === false
+    if (argv["config"] === false) {
-      ? null
+      logger.debug("'--no-config' option found, skip loading config file.");
-      : resolver.resolveConfig.sync(filePath, { config: argv["config"] });
+      return null;
+    }
+
+    logger.debug(
+      argv["config"]
+        ? `load config file from '${argv["config"]}'`
+        : `resolve config from '${filePath}'`
+    );
+    const options = resolver.resolveConfig.sync(filePath, {
+      config: argv["config"]
+    });
+
+    logger.debug("loaded options `" + JSON.stringify(options) + "`");
+    return options;
   } catch (error) {
-    console.error("Error: Invalid configuration file.");
+    logger.error("Invalid configuration file: " + error.message);
-    console.error(error.message);
     process.exit(2);
   }
 }
 
 function getOptionsForFile(argv, filepath) {
   const options = getOptionsOrDie(argv, filepath);
-  return Object.assign(
+
+  const appliedOptions = Object.assign(
     { filepath },
     applyConfigPrecedence(
       argv,
       options && normalizeConfig("api", options, constant.detailedOptionMap)
     )
   );
+
+  logger.debug(
+    `applied config-precedence (${argv["config-precedence"]}): ` +
+      `${JSON.stringify(appliedOptions)}`
+  );
+  return appliedOptions;
 }
 
 function parseArgsToOptions(argv, overrideDefaults) {
@@ -199,7 +219,7 @@ function applyConfigPrecedence(argv, options) {
         return options || parseArgsToOptions(argv);
     }
   } catch (error) {
-    console.error(error.toString());
+    logger.error(error.toString());
     process.exit(2);
   }
 }
@@ -235,7 +255,7 @@ function eachFilename(argv, patterns, callback) {
     ignoreText = fs.readFileSync(ignoreFilePath, "utf8");
   } catch (readError) {
     if (readError.code !== "ENOENT") {
-      console.error(`Unable to read ${ignoreFilePath}:`, readError);
+      logger.error(`Unable to read ${ignoreFilePath}: ` + readError.message);
       process.exit(2);
     }
   }
@@ -252,7 +272,7 @@ function eachFilename(argv, patterns, callback) {
       .map(filePath => path.relative(process.cwd(), filePath));
 
     if (filePaths.length === 0) {
-      console.error(`No matching files. Patterns tried: ${patterns.join(" ")}`);
+      logger.error(`No matching files. Patterns tried: ${patterns.join(" ")}`);
       process.exitCode = 2;
       return;
     }
@@ -262,8 +282,8 @@ function eachFilename(argv, patterns, callback) {
         callback(filePath, getOptionsForFile(argv, filePath))
       );
   } catch (error) {
-    console.error(
+    logger.error(
-      `Unable to expand glob patterns: ${patterns.join(" ")}\n${error}`
+      `Unable to expand glob patterns: ${patterns.join(" ")}\n${error.message}`
     );
     // Don't exit the process if one pattern failed
     process.exitCode = 2;
@@ -284,7 +304,7 @@ function formatFiles(argv) {
       // Add newline to split errors from filename line.
       process.stdout.write("\n");
 
-      console.error(`Unable to read file: ${filename}\n${error}`);
+      logger.error(`Unable to read file: ${filename}\n${error.message}`);
       // Don't exit the process if one file failed
       process.exitCode = 2;
       return;
@@ -335,7 +355,7 @@ function formatFiles(argv) {
         try {
           fs.writeFileSync(filename, output, "utf8");
         } catch (error) {
-          console.error(`Unable to write file: ${filename}\n${error}`);
+          logger.error(`Unable to write file: ${filename}\n${error.message}`);
           // Don't exit the process if one file failed
           process.exitCode = 2;
         }
@@ -470,14 +490,14 @@ function getOptionWithLevenSuggestion(options, optionName) {
 
   if (suggestedOptionNameContainer !== undefined) {
     const suggestedOptionName = suggestedOptionNameContainer.value;
-    console.warn(
+    logger.warn(
-      `Unknown option name "${optionName}", did you mean "${suggestedOptionName}"?\n`
+      `Unknown option name "${optionName}", did you mean "${suggestedOptionName}"?`
     );
 
     return options[suggestedOptionNameContainer.index];
   }
 
-  console.warn(`Unknown option name "${optionName}"\n`);
+  logger.warn(`Unknown option name "${optionName}"`);
   return options.find(option => option.name === "help");
 }
 
@@ -562,7 +582,8 @@ function normalizeConfig(type, rawConfig, options) {
 
   options = options || {};
 
-  const consoleWarn = options.warning === false ? () => {} : console.warn;
+  const consoleWarn =
+    options.warning === false ? () => {} : logger.warn.bind(logger);
 
   const normalized = {};
 
@@ -585,11 +606,12 @@ function normalizeConfig(type, rawConfig, options) {
 
     // unknown option
     if (option === undefined) {
-      // no need to warn for CLI since it's already warned in minimist
       if (type === "api") {
-        console.warn(`Ignored unknown option: ${rawKey}`);
+        consoleWarn(`Ignored unknown option: ${rawKey}`);
+      } else {
+        const optionName = rawValue === false ? `no-${rawKey}` : rawKey;
+        consoleWarn(`Ignored unknown option: --${optionName}`);
       }
-
       return;
     }
 
@@ -609,6 +631,7 @@ function normalizeConfig(type, rawConfig, options) {
       }
     }
 
+    try {
       switch (option.type) {
         case "int":
           validator.validateIntOption(type, value, option);
@@ -622,6 +645,10 @@ function normalizeConfig(type, rawConfig, options) {
           normalized[rawKey] = value;
           break;
       }
+    } catch (error) {
+      logger.error(error.message);
+      process.exit(2);
+    }
   });
 
   return normalized;

src/cli-validator.js

@@ -1,15 +1,16 @@
 "use strict";
 
 const camelCase = require("camelcase");
+const logger = require("./cli-logger");
 
 function validateArgv(argv) {
   if (argv["write"] && argv["debug-check"]) {
-    console.error("Cannot use --write and --debug-check together.");
+    logger.error("Cannot use --write and --debug-check together.");
     process.exit(1);
   }
 
   if (argv["find-config-path"] && argv.__filePatterns.length) {
-    console.error("Cannot use --find-config-path with multiple files");
+    logger.error("Cannot use --find-config-path with multiple files");
     process.exit(1);
   }
 }

src/cli.js

@@ -6,12 +6,17 @@ const prettier = eval("require")("../index");
 const constant = require("./cli-constant");
 const util = require("./cli-util");
 const validator = require("./cli-validator");
+const logger = require("./cli-logger");
 
 function run(args) {
-  const argv = util.normalizeConfig(
+  const rawArgv = minimist(args, constant.minimistOptions);
-    "cli",
+
-    minimist(args, constant.minimistOptions)
+  process.env[logger.ENV_LOG_LEVEL] =
-  );
+    rawArgv["loglevel"] || constant.detailedOptionMap["loglevel"].default;
+
+  const argv = util.normalizeConfig("cli", rawArgv);
+
+  logger.debug(`normalized argv: ${JSON.stringify(argv)}`);
 
   argv.__args = args;
   argv.__filePatterns = argv["_"];

tests_integration/__tests__/__snapshots__/arg-parsing.js.snap

@@ -10,7 +10,7 @@ exports[`boolean flags do not swallow the next argument (stdout) 1`] = `
 exports[`boolean flags do not swallow the next argument (write) 1`] = `Array []`;
 
 exports[`deprecated option values are warned (stderr) 1`] = `
-"\`--trailing-comma\` without an argument is deprecated. Prettier now treats it as: \`--trailing-comma=es5\`.
+"[warn] \`--trailing-comma\` without an argument is deprecated. Prettier now treats it as: \`--trailing-comma=es5\`.
 "
 `;
 
@@ -22,7 +22,7 @@ exports[`deprecated option values are warned (stdout) 1`] = `
 exports[`deprecated option values are warned (write) 1`] = `Array []`;
 
 exports[`deprecated options are warned (stderr) 1`] = `
-"\`--flow-parser\` is deprecated. Use \`--parser flow\` instead.
+"[warn] \`--flow-parser\` is deprecated. Use \`--parser flow\` instead.
 "
 `;
 
@@ -43,8 +43,7 @@ exports[`negated options work (stdout) 1`] = `
 exports[`negated options work (write) 1`] = `Array []`;
 
 exports[`unknown negated options are warned (stderr) 1`] = `
-"Ignored unknown option: --no-unknown
+"[warn] Ignored unknown option: --no-unknown
-
 "
 `;
 
@@ -56,8 +55,7 @@ exports[`unknown negated options are warned (stdout) 1`] = `
 exports[`unknown negated options are warned (write) 1`] = `Array []`;
 
 exports[`unknown options are warned (stderr) 1`] = `
-"Ignored unknown option: --unknown
+"[warn] Ignored unknown option: --unknown
-
 "
 `;
 

tests_integration/__tests__/__snapshots__/config-invalid.js.snap

@@ -1,7 +1,7 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`show warning with unknown option (stderr) 1`] = `
-"Ignored unknown option: hello
+"[warn] Ignored unknown option: hello
 "
 `;
 
@@ -10,8 +10,7 @@ exports[`show warning with unknown option (stdout) 1`] = `""`;
 exports[`show warning with unknown option (write) 1`] = `Array []`;
 
 exports[`throw error with invalid config format (stderr) 1`] = `
-"Error: Invalid configuration file.
+"[error] Invalid configuration file: Failed to parse \\"<cwd>/tests_integration/cli/config/invalid/file/.prettierrc\\" as JSON, JS, or YAML.
-Failed to parse \\"<cwd>/tests_integration/cli/config/invalid/file/.prettierrc\\" as JSON, JS, or YAML.
 "
 `;
 
@@ -20,8 +19,9 @@ exports[`throw error with invalid config format (stdout) 1`] = `""`;
 exports[`throw error with invalid config format (write) 1`] = `Array []`;
 
 exports[`throw error with invalid config option (int) (stderr) 1`] = `
-"Invalid tabWidth value.
+"[error] Invalid tabWidth value.
-Expected an integer, but received: 0.5"
+[error] Expected an integer, but received: 0.5
+"
 `;
 
 exports[`throw error with invalid config option (int) (stdout) 1`] = `""`;
@@ -29,8 +29,9 @@ exports[`throw error with invalid config option (int) (stdout) 1`] = `""`;
 exports[`throw error with invalid config option (int) (write) 1`] = `Array []`;
 
 exports[`throw error with invalid config option (trailingComma) (stderr) 1`] = `
-"Invalid option for trailingComma.
+"[error] Invalid option for trailingComma.
-Expected \\"none\\", \\"es5\\" or \\"all\\", but received: \\"wow\\""
+[error] Expected \\"none\\", \\"es5\\" or \\"all\\", but received: \\"wow\\"
+"
 `;
 
 exports[`throw error with invalid config option (trailingComma) (stdout) 1`] = `""`;
@@ -38,8 +39,9 @@ exports[`throw error with invalid config option (trailingComma) (stdout) 1`] = `
 exports[`throw error with invalid config option (trailingComma) (write) 1`] = `Array []`;
 
 exports[`throw error with invalid config precedence option (configPrecedence) (stderr) 1`] = `
-"Invalid option for --config-precedence.
+"[error] Invalid option for --config-precedence.
-Expected \\"cli-override\\", \\"file-override\\" or \\"prefer-file\\", but received: \\"option/configPrecedence\\""
+[error] Expected \\"cli-override\\", \\"file-override\\" or \\"prefer-file\\", but received: \\"option/configPrecedence\\"
+"
 `;
 
 exports[`throw error with invalid config precedence option (configPrecedence) (stdout) 1`] = `""`;
@@ -47,8 +49,7 @@ exports[`throw error with invalid config precedence option (configPrecedence) (s
 exports[`throw error with invalid config precedence option (configPrecedence) (write) 1`] = `Array []`;
 
 exports[`throw error with invalid config target (directory) (stderr) 1`] = `
-"Error: Invalid configuration file.
+"[error] Invalid configuration file: EISDIR: illegal operation on a directory, read
-EISDIR: illegal operation on a directory, read
 "
 `;
 

tests_integration/__tests__/__snapshots__/debug-check.js.snap

@@ -5,56 +5,56 @@ exports[`checks stdin with --debug-check (write) 1`] = `Array []`;
 exports[`doesn't crash when --debug-check is passed (write) 1`] = `Array []`;
 
 exports[`show diff for 2+ error files with --debug-check (stderr) 1`] = `
-"a.js: ast(input) !== ast(prettier(input))
+"[error] a.js: ast(input) !== ast(prettier(input))
-Index: 
+[error] Index:
-===================================================================
+[error] ===================================================================
---- 	
+[error] ---
-+++ 	
+[error] +++
-@@ -17,6 +17,6 @@
+[error] @@ -17,6 +17,6 @@
-                   \\"method\\": false,
+[error]                    \\"method\\": false,
-                   \\"key\\": {
+[error]                    \\"key\\": {
--                    \\"type\\": \\"StringLiteral\\",
+[error] -                    \\"type\\": \\"StringLiteral\\",
--                    \\"value\\": \\"a\\"
+[error] -                    \\"value\\": \\"a\\"
-+                    \\"type\\": \\"Identifier\\",
+[error] +                    \\"type\\": \\"Identifier\\",
-+                    \\"name\\": \\"a\\"
+[error] +                    \\"name\\": \\"a\\"
-                   },
+[error]                    },
-                   \\"computed\\": false,
+[error]                    \\"computed\\": false,
-
+[error]
-Index: 
+[error] Index:
-===================================================================
+[error] ===================================================================
---- 	
+[error] ---
-+++ 	
+[error] +++
-@@ -1,3 +1,3 @@
+[error] @@ -1,3 +1,3 @@
- const a = {
+[error]  const a = {
--    'a': 1
+[error] -    'a': 1
-+  a: 1
+[error] +  a: 1
- };
+[error]  };
-
+[error]
-b.js: ast(input) !== ast(prettier(input))
+[error] b.js: ast(input) !== ast(prettier(input))
-Index: 
+[error] Index:
-===================================================================
+[error] ===================================================================
---- 	
+[error] ---
-+++ 	
+[error] +++
-@@ -17,6 +17,6 @@
+[error] @@ -17,6 +17,6 @@
-                   \\"method\\": false,
+[error]                    \\"method\\": false,
-                   \\"key\\": {
+[error]                    \\"key\\": {
--                    \\"type\\": \\"StringLiteral\\",
+[error] -                    \\"type\\": \\"StringLiteral\\",
--                    \\"value\\": \\"b\\"
+[error] -                    \\"value\\": \\"b\\"
-+                    \\"type\\": \\"Identifier\\",
+[error] +                    \\"type\\": \\"Identifier\\",
-+                    \\"name\\": \\"b\\"
+[error] +                    \\"name\\": \\"b\\"
-                   },
+[error]                    },
-                   \\"computed\\": false,
+[error]                    \\"computed\\": false,
-
+[error]
-Index: 
+[error] Index:
-===================================================================
+[error] ===================================================================
---- 	
+[error] ---
-+++ 	
+[error] +++
-@@ -1,3 +1,3 @@
+[error] @@ -1,3 +1,3 @@
- const b = {
+[error]  const b = {
--    'b': 2
+[error] -    'b': 2
-+  b: 2
+[error] +  b: 2
- };
+[error]  };
-
+[error]
 "
 `;
 

tests_integration/__tests__/__snapshots__/early-exit.js.snap

@@ -155,6 +155,26 @@ exports[`show detailed usage with --help list-different (stdout) 1`] = `
 
 exports[`show detailed usage with --help list-different (write) 1`] = `Array []`;
 
+exports[`show detailed usage with --help loglevel (stderr) 1`] = `""`;
+
+exports[`show detailed usage with --help loglevel (stdout) 1`] = `
+"--loglevel <silent|error|warn|debug>
+
+  What level of logs to report.
+
+Valid options:
+
+  silent   
+  error    
+  warn     
+  debug    
+
+Default: warn
+"
+`;
+
+exports[`show detailed usage with --help loglevel (write) 1`] = `Array []`;
+
 exports[`show detailed usage with --help no-bracket-spacing (stderr) 1`] = `""`;
 
 exports[`show detailed usage with --help no-bracket-spacing (stdout) 1`] = `
@@ -475,6 +495,9 @@ Other options:
                            Example: --help write
   --insert-pragma          Insert @format pragma into file's first docblock comment.
                            Defaults to false.
+  --loglevel <silent|error|warn|debug>
+                           What level of logs to report.
+                           Defaults to warn.
   --require-pragma         Require either '@prettier' or '@format' to be present in the file's first docblock comment
                            in order for it to be formatted.
                            Defaults to false.
@@ -493,8 +516,7 @@ exports[`show version with --version (stderr) 1`] = `""`;
 exports[`show version with --version (write) 1`] = `Array []`;
 
 exports[`show warning with --help not-found (stderr) 1`] = `
-"Unknown option name \\"not-found\\"
+"[warn] Unknown option name \\"not-found\\"
-
 "
 `;
 
@@ -507,8 +529,7 @@ exports[`show warning with --help not-found (stdout) 1`] = `
 `;
 
 exports[`show warning with --help not-found (typo) (stderr) 1`] = `
-"Unknown option name \\"parserr\\", did you mean \\"parser\\"?
+"[warn] Unknown option name \\"parserr\\", did you mean \\"parser\\"?
-
 "
 `;
 
@@ -605,6 +626,9 @@ Other options:
                            Example: --help write
   --insert-pragma          Insert @format pragma into file's first docblock comment.
                            Defaults to false.
+  --loglevel <silent|error|warn|debug>
+                           What level of logs to report.
+                           Defaults to warn.
   --require-pragma         Require either '@prettier' or '@format' to be present in the file's first docblock comment
                            in order for it to be formatted.
                            Defaults to false.
@@ -619,7 +643,7 @@ Other options:
 exports[`throw error and show usage with something unexpected (write) 1`] = `Array []`;
 
 exports[`throw error with --find-config-path + multiple files (stderr) 1`] = `
-"Cannot use --find-config-path with multiple files
+"[error] Cannot use --find-config-path with multiple files
 "
 `;
 
@@ -628,7 +652,7 @@ exports[`throw error with --find-config-path + multiple files (stdout) 1`] = `""
 exports[`throw error with --find-config-path + multiple files (write) 1`] = `Array []`;
 
 exports[`throw error with --write + --debug-check (stderr) 1`] = `
-"Cannot use --write and --debug-check together.
+"[error] Cannot use --write and --debug-check together.
 "
 `;
 

tests_integration/__tests__/__snapshots__/invalid-ignore.js.snap

@@ -1,7 +1,7 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`throw error with invalid ignore (stderr) 1`] = `
-"Unable to read <cwd>/tests_integration/cli/invalid-ignore/.prettierignore:
+"[error] Unable to read <cwd>/tests_integration/cli/invalid-ignore/.prettierignore: EISDIR: illegal operation on a directory, read
 "
 `;
 

tests_integration/__tests__/__snapshots__/multiple-patterns.js.snap

@@ -72,7 +72,7 @@ directory/nested-directory/nested-directory-file.js
 exports[`multiple patterns with non exists pattern (write) 1`] = `Array []`;
 
 exports[`multiple patterns, throw error and exit with non zero code on non existing files (stderr) 1`] = `
-"No matching files. Patterns tried: non-existent.js other-non-existent.js !**/node_modules/** !./node_modules/**
+"[error] No matching files. Patterns tried: non-existent.js other-non-existent.js !**/node_modules/** !./node_modules/**
 "
 `;
 

tests_integration/__tests__/__snapshots__/stdin-filepath.js.snap

@@ -12,9 +12,9 @@ exports[`format correctly if stdin content compatible with stdin-filepath (stdou
 exports[`format correctly if stdin content compatible with stdin-filepath (write) 1`] = `Array []`;
 
 exports[`throw error if stdin content incompatible with stdin-filepath (stderr) 1`] = `
-"stdin: SyntaxError: Unexpected token (1:1)
+"[error] stdin: SyntaxError: Unexpected token (1:1)
-> 1 | .name { display: none; }
+[error] > 1 | .name { display: none; }
-    | ^
+[error]     | ^
 "
 `;
 

tests_integration/__tests__/__snapshots__/syntax-error.js.snap

@@ -1,9 +1,9 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`exits with non-zero code when input has a syntax error (stderr) 1`] = `
-"stdin: SyntaxError: Unexpected token, expected ; (1:2)
+"[error] stdin: SyntaxError: Unexpected token, expected ; (1:2)
-> 1 | a.2
+[error] > 1 | a.2
-    |  ^
+[error]     |  ^
 "
 `;
 

tests_integration/__tests__/__snapshots__/with-config-precedence.js.snap

@@ -192,8 +192,9 @@ function rcYaml() {
 exports[`CLI overrides take precedence without --config-precedence (write) 1`] = `Array []`;
 
 exports[`CLI validate options with --config-precedence cli-override (stderr) 1`] = `
-"Invalid printWidth value.
+"[error] Invalid printWidth value.
-Expected an integer, but received: 0.5"
+[error] Expected an integer, but received: 0.5
+"
 `;
 
 exports[`CLI validate options with --config-precedence cli-override (stdout) 1`] = `""`;
@@ -201,8 +202,9 @@ exports[`CLI validate options with --config-precedence cli-override (stdout) 1`]
 exports[`CLI validate options with --config-precedence cli-override (write) 1`] = `Array []`;
 
 exports[`CLI validate options with --config-precedence file-override (stderr) 1`] = `
-"Invalid printWidth value.
+"[error] Invalid printWidth value.
-Expected an integer, but received: 0.5"
+[error] Expected an integer, but received: 0.5
+"
 `;
 
 exports[`CLI validate options with --config-precedence file-override (stdout) 1`] = `""`;
@@ -210,8 +212,9 @@ exports[`CLI validate options with --config-precedence file-override (stdout) 1`
 exports[`CLI validate options with --config-precedence file-override (write) 1`] = `Array []`;
 
 exports[`CLI validate options with --config-precedence prefer-file (stderr) 1`] = `
-"Invalid printWidth value.
+"[error] Invalid printWidth value.
-Expected an integer, but received: 0.5"
+[error] Expected an integer, but received: 0.5
+"
 `;
 
 exports[`CLI validate options with --config-precedence prefer-file (stdout) 1`] = `""`;

tests_integration/__tests__/__snapshots__/write.js.snap

@@ -8,9 +8,9 @@ exports[`do not write file with --write + formatted file (stdout) 1`] = `
 `;
 
 exports[`do not write file with --write + invalid file (stderr) 1`] = `
-"invalid.js: SyntaxError: Unexpected token, expected ; (1:6)
+"[error] invalid.js: SyntaxError: Unexpected token, expected ; (1:6)
-> 1 | this is invalid!
+[error] > 1 | this is invalid!
-    |      ^
+[error]     |      ^
 "
 `;
 

tests_integration/__tests__/loglevel.js

@@ -0,0 +1,40 @@
+"use strict";
+
+const runPrettier = require("../runPrettier");
+
+test("do not show logs with --loglevel silent", () => {
+  runPrettierWithLogLevel("silent", null);
+});
+
+test("do not show warnings with --loglevel error", () => {
+  runPrettierWithLogLevel("error", ["[error]"]);
+});
+
+test("show errors and warnings with --loglevel warn", () => {
+  runPrettierWithLogLevel("warn", ["[error]", "[warn]"]);
+});
+
+test("show all logs with --loglevel debug", () => {
+  runPrettierWithLogLevel("debug", ["[error]", "[warn]", "[debug]"]);
+});
+
+function runPrettierWithLogLevel(logLevel, patterns) {
+  const result = runPrettier("cli/loglevel", [
+    "--loglevel",
+    logLevel,
+    "--unknown-option",
+    "--parser",
+    "unknown-parser",
+    "not-found.js"
+  ]);
+
+  expect(result).not.toEqual(0);
+
+  if (patterns) {
+    patterns.forEach(pattern => {
+      expect(result.stderr).toMatch(pattern);
+    });
+  } else {
+    expect(result.stderr).toMatch(/^\s*$/);
+  }
+}

tests_integration/cli/loglevel/.prettierrc

@@ -0,0 +1,3 @@
+{
+    "printWidth": 999
+}

tests_integration/runPrettier.js

@@ -3,6 +3,7 @@
 const fs = require("fs");
 const path = require("path");
 const stripAnsi = require("strip-ansi");
+const ENV_LOG_LEVEL = require("../src/cli-logger").ENV_LOG_LEVEL;
 
 const isProduction = process.env.NODE_ENV === "production";
 const prettierApi = isProduction ? "../dist/index" : "../index";
@@ -55,6 +56,7 @@ function runPrettier(dir, args, options) {
   const originalExitCode = process.exitCode;
   const originalStdinIsTTY = process.stdin.isTTY;
   const originalStdoutIsTTY = process.stdout.isTTY;
+  const originalEnvLogLevel = process.env[ENV_LOG_LEVEL];
 
   process.chdir(normalizeDir(dir));
   process.stdin.isTTY = !!options.isTTY;
@@ -84,6 +86,7 @@ function runPrettier(dir, args, options) {
     process.exitCode = originalExitCode;
     process.stdin.isTTY = originalStdinIsTTY;
     process.stdout.isTTY = originalStdoutIsTTY;
+    process.env[ENV_LOG_LEVEL] = originalEnvLogLevel;
     jest.restoreAllMocks();
   }
 
@@ -113,7 +116,7 @@ function runPrettier(dir, args, options) {
     return result;
   };
 
-  return { test: testResult };
+  return Object.assign({ test: testResult }, result);
 
   function appendStdout(text) {
     if (status === undefined) {