feat: Add "--json" flag to deno lint (#6940)

Co-authored-by: JackSkylark <jdslaughter44@gmail.com>

7 files changed, 233 insertions, 37 deletions

diff --git a/cli/flags.rs b/cli/flags.rs
index 6c58238de..537e768f2 100644
--- a/cli/flags.rs
+++ b/cli/flags.rs
@@ -57,6 +57,7 @@ pub enum DenoSubcommand {
     files: Vec<String>,
     ignore: Vec<String>,
     rules: bool,
+    json: bool,
   },
   Repl,
   Run {
@@ -636,10 +637,12 @@ fn lint_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
     None => vec![],
   };
   let rules = matches.is_present("rules");
+  let json = matches.is_present("json");
   flags.subcommand = DenoSubcommand::Lint {
     files,
     rules,
     ignore,
+    json,
   };
 }
 
@@ -1008,6 +1011,9 @@ fn lint_subcommand<'a, 'b>() -> App<'a, 'b> {
   deno lint --unstable
   deno lint --unstable myfile1.ts myfile2.js
 
+Print result as JSON:
+  deno lint --unstable --json
+
 List available rules:
   deno lint --unstable --rules
 
@@ -1042,6 +1048,12 @@ Ignore linting a file by adding an ignore comment at the top of the file:
         .help("Ignore linting particular source files."),
     )
     .arg(
+      Arg::with_name("json")
+        .long("json")
+        .help("Output lint result in JSON format.")
+        .takes_value(false),
+    )
+    .arg(
       Arg::with_name("files")
         .takes_value(true)
         .multiple(true)
@@ -1761,6 +1773,7 @@ mod tests {
         subcommand: DenoSubcommand::Lint {
           files: vec!["script_1.ts".to_string(), "script_2.ts".to_string()],
           rules: false,
+          json: false,
           ignore: vec![],
         },
         unstable: true,
@@ -1780,6 +1793,7 @@ mod tests {
         subcommand: DenoSubcommand::Lint {
           files: vec![],
           rules: false,
+          json: false,
           ignore: svec!["script_1.ts", "script_2.ts"],
         },
         unstable: true,
@@ -1794,6 +1808,28 @@ mod tests {
         subcommand: DenoSubcommand::Lint {
           files: vec![],
           rules: true,
+          json: false,
+          ignore: vec![],
+        },
+        unstable: true,
+        ..Flags::default()
+      }
+    );
+
+    let r = flags_from_vec_safe(svec![
+      "deno",
+      "lint",
+      "--unstable",
+      "--json",
+      "script_1.ts"
+    ]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        subcommand: DenoSubcommand::Lint {
+          files: vec!["script_1.ts".to_string()],
+          rules: false,
+          json: true,
           ignore: vec![],
         },
         unstable: true,
diff --git a/cli/lint.rs b/cli/lint.rs
index 3e9380d9d..bf6dc16b6 100644
--- a/cli/lint.rs
+++ b/cli/lint.rs
@@ -6,7 +6,6 @@
 //! At the moment it is only consumed using CLI but in
 //! the future it can be easily extended to provide
 //! the same functions as ops available in JS runtime.
-
 use crate::colors;
 use crate::file_fetcher::map_file_extension;
 use crate::fmt::collect_files;
@@ -19,15 +18,29 @@ use deno_lint::linter::Linter;
 use deno_lint::linter::LinterBuilder;
 use deno_lint::rules;
 use deno_lint::rules::LintRule;
+use serde::Serialize;
 use std::fs;
 use std::path::PathBuf;
-use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 use swc_ecmascript::parser::Syntax;
 
+pub enum LintReporterKind {
+  Pretty,
+  Json,
+}
+
+fn create_reporter(kind: LintReporterKind) -> Box<dyn LintReporter + Send> {
+  match kind {
+    LintReporterKind::Pretty => Box::new(PrettyLintReporter::new()),
+    LintReporterKind::Json => Box::new(JsonLintReporter::new()),
+  }
+}
+
 pub async fn lint_files(
   args: Vec<String>,
   ignore: Vec<String>,
+  json: bool,
 ) -> Result<(), ErrBox> {
   let mut target_files = collect_files(args)?;
   if !ignore.is_empty() {
@@ -38,28 +51,32 @@ pub async fn lint_files(
   }
   debug!("Found {} files", target_files.len());
 
-  let error_count = Arc::new(AtomicUsize::new(0));
+  let has_error = Arc::new(AtomicBool::new(false));
 
-  // prevent threads outputting at the same time
-  let output_lock = Arc::new(Mutex::new(0));
+  let reporter_kind = if json {
+    LintReporterKind::Json
+  } else {
+    LintReporterKind::Pretty
+  };
+  let reporter_lock = Arc::new(Mutex::new(create_reporter(reporter_kind)));
 
   run_parallelized(target_files, {
-    let error_count = error_count.clone();
+    let reporter_lock = reporter_lock.clone();
+    let has_error = has_error.clone();
     move |file_path| {
       let r = lint_file(file_path.clone());
+      let mut reporter = reporter_lock.lock().unwrap();
 
       match r {
         Ok(file_diagnostics) => {
-          error_count.fetch_add(file_diagnostics.len(), Ordering::SeqCst);
-          let _g = output_lock.lock().unwrap();
           for d in file_diagnostics.iter() {
-            let fmt_diagnostic = format_diagnostic(d);
-            eprintln!("{}\n", fmt_diagnostic);
+            has_error.store(true, Ordering::Relaxed);
+            reporter.visit(&d);
           }
         }
         Err(err) => {
-          eprintln!("Error linting: {}", file_path.to_string_lossy());
-          eprintln!("   {}", err);
+          has_error.store(true, Ordering::Relaxed);
+          reporter.visit_error(&file_path.to_string_lossy().to_string(), &err);
         }
       }
       Ok(())
@@ -67,9 +84,11 @@ pub async fn lint_files(
   })
   .await?;
 
-  let error_count = error_count.load(Ordering::SeqCst);
-  if error_count > 0 {
-    eprintln!("Found {} problems", error_count);
+  let has_error = has_error.load(Ordering::Relaxed);
+
+  reporter_lock.lock().unwrap().close();
+
+  if has_error {
     std::process::exit(1);
   }
 
@@ -170,21 +189,106 @@ fn lint_file(file_path: PathBuf) -> Result<Vec<LintDiagnostic>, ErrBox> {
   Ok(file_diagnostics)
 }
 
-fn format_diagnostic(d: &LintDiagnostic) -> String {
-  let pretty_message =
-    format!("({}) {}", colors::gray(&d.code), d.message.clone());
-
-  fmt_errors::format_stack(
-    true,
-    &pretty_message,
-    Some(&d.line_src),
-    Some(d.location.col as i64),
-    Some((d.location.col + d.snippet_length) as i64),
-    &[fmt_errors::format_location(
-      &d.location.filename,
-      d.location.line as i64,
-      d.location.col as i64,
-    )],
-    0,
-  )
+trait LintReporter {
+  fn visit(&mut self, d: &LintDiagnostic);
+  fn visit_error(&mut self, file_path: &str, err: &ErrBox);
+  fn close(&mut self);
+}
+
+#[derive(Serialize)]
+struct LintError {
+  file_path: String,
+  message: String,
+}
+
+struct PrettyLintReporter {
+  lint_count: u32,
+}
+
+impl PrettyLintReporter {
+  fn new() -> PrettyLintReporter {
+    PrettyLintReporter { lint_count: 0 }
+  }
+}
+
+impl LintReporter for PrettyLintReporter {
+  fn visit(&mut self, d: &LintDiagnostic) {
+    self.lint_count += 1;
+
+    let pretty_message =
+      format!("({}) {}", colors::gray(&d.code), d.message.clone());
+
+    let message = fmt_errors::format_stack(
+      true,
+      &pretty_message,
+      Some(&d.line_src),
+      Some(d.location.col as i64),
+      Some((d.location.col + d.snippet_length) as i64),
+      &[fmt_errors::format_location(
+        &d.location.filename,
+        d.location.line as i64,
+        d.location.col as i64,
+      )],
+      0,
+    );
+
+    eprintln!("{}\n", message);
+  }
+
+  fn visit_error(&mut self, file_path: &str, err: &ErrBox) {
+    eprintln!("Error linting: {}", file_path);
+    eprintln!("   {}", err);
+  }
+
+  fn close(&mut self) {
+    match self.lint_count {
+      1 => eprintln!("Found 1 problem"),
+      n if n > 1 => eprintln!("Found {} problems", self.lint_count),
+      _ => (),
+    }
+  }
+}
+
+#[derive(Serialize)]
+struct JsonLintReporter {
+  diagnostics: Vec<LintDiagnostic>,
+  errors: Vec<LintError>,
+}
+
+impl JsonLintReporter {
+  fn new() -> JsonLintReporter {
+    JsonLintReporter {
+      diagnostics: Vec::new(),
+      errors: Vec::new(),
+    }
+  }
+}
+
+impl LintReporter for JsonLintReporter {
+  fn visit(&mut self, d: &LintDiagnostic) {
+    self.diagnostics.push(d.clone());
+  }
+
+  fn visit_error(&mut self, file_path: &str, err: &ErrBox) {
+    self.errors.push(LintError {
+      file_path: file_path.to_string(),
+      message: err.to_string(),
+    });
+  }
+
+  fn close(&mut self) {
+    // Sort so that we guarantee a deterministic output which is useful for tests
+    self
+      .diagnostics
+      .sort_by(|a, b| get_sort_key(&a).cmp(&get_sort_key(&b)));
+
+    let json = serde_json::to_string_pretty(&self);
+    eprintln!("{}", json.unwrap());
+  }
+}
+
+pub fn get_sort_key(a: &LintDiagnostic) -> String {
+  let location = &a.location;
+
+  return format!("{}:{}:{}", location.filename, location.line, location.col);
 }
diff --git a/cli/main.rs b/cli/main.rs
index 27948e14f..b5eb0b745 100644
--- a/cli/main.rs
+++ b/cli/main.rs
@@ -346,6 +346,7 @@ async fn lint_command(
   files: Vec<String>,
   list_rules: bool,
   ignore: Vec<String>,
+  json: bool,
 ) -> Result<(), ErrBox> {
   if !flags.unstable {
     exit_unstable("lint");
@@ -356,7 +357,7 @@ async fn lint_command(
     return Ok(());
   }
 
-  lint::lint_files(files, ignore).await
+  lint::lint_files(files, ignore, json).await
 }
 
 async fn cache_command(flags: Flags, files: Vec<String>) -> Result<(), ErrBox> {
@@ -738,7 +739,8 @@ pub fn main() {
       files,
       rules,
       ignore,
-    } => lint_command(flags, files, rules, ignore).boxed_local(),
+      json,
+    } => lint_command(flags, files, rules, ignore, json).boxed_local(),
     DenoSubcommand::Repl => run_repl(flags).boxed_local(),
     DenoSubcommand::Run { script } => run_command(flags, script).boxed_local(),
     DenoSubcommand::Test {
diff --git a/cli/tests/integration_tests.rs b/cli/tests/integration_tests.rs
index bb7ba0d6f..6e487d12f 100644
--- a/cli/tests/integration_tests.rs
+++ b/cli/tests/integration_tests.rs
@@ -2216,14 +2216,21 @@ itest!(deno_lint {
   exit_code: 1,
 });
 
+itest!(deno_lint_json {
+  args:
+    "lint --unstable --json lint/file1.js lint/file2.ts lint/ignored_file.ts lint/malformed.js",
+  output: "lint/expected_json.out",
+  exit_code: 1,
+});
+
 itest!(deno_lint_ignore {
-  args: "lint --unstable --ignore=lint/file1.js lint/",
+  args: "lint --unstable --ignore=lint/file1.js,lint/malformed.js lint/",
   output: "lint/expected_ignore.out",
   exit_code: 1,
 });
 
 itest!(deno_lint_glob {
-  args: "lint --unstable lint/",
+  args: "lint --unstable --ignore=lint/malformed.js lint/",
   output: "lint/expected_glob.out",
   exit_code: 1,
 });
diff --git a/cli/tests/lint/expected_ignore.out b/cli/tests/lint/expected_ignore.out
index 6041d1c6a..02b9d917c 100644
--- a/cli/tests/lint/expected_ignore.out
+++ b/cli/tests/lint/expected_ignore.out
@@ -1,2 +1,2 @@
 [WILDCARD]
-Found 1 problems
+Found 1 problem
diff --git a/cli/tests/lint/expected_json.out b/cli/tests/lint/expected_json.out
new file mode 100644
index 000000000..b4ce63395
--- /dev/null
+++ b/cli/tests/lint/expected_json.out
@@ -0,0 +1,43 @@
+{
+  "diagnostics": [
+    {
+      "location": {
+        "filename": "[WILDCARD]",
+        "line": 1,
+        "col": 0
+      },
+      "message": "Ignore directive requires lint rule code",
+      "code": "ban-untagged-ignore",
+      "line_src": "// deno-lint-ignore",
+      "snippet_length": 19
+    },
+    {
+      "location": {
+        "filename": "[WILDCARD]",
+        "line": 2,
+        "col": 14
+      },
+      "message": "Empty block statement",
+      "code": "no-empty",
+      "line_src": "while (false) {}",
+      "snippet_length": 2
+    },
+    {
+      "location": {
+        "filename": "[WILDCARD]",
+        "line": 3,
+        "col": 12
+      },
+      "message": "Empty block statement",
+      "code": "no-empty",
+      "line_src": "} catch (e) {}",
+      "snippet_length": 2
+    }
+  ],
+  "errors": [
+    {
+      "file_path": "[WILDCARD]malformed.js",
+      "message": "Expected RBrace, got None at [WILDCARD]malformed.js:4:15"
+    }
+  ]
+}
diff --git a/cli/tests/lint/malformed.js b/cli/tests/lint/malformed.js
new file mode 100644
index 000000000..5ad4650d6
--- /dev/null
+++ b/cli/tests/lint/malformed.js
@@ -0,0 +1,4 @@
+// deno-fmt-ignore-file
+
+// intentionally malformed file
+export class A {
\ No newline at end of file