logger: bound the excerpt printed for an error on a long line

src/ast/lib.rs

@@ -978,11 +978,19 @@ impl Data {
 
         if let Some(location) = &self.location {
             if let Some(line_text_) = location.line_text.as_deref() {
-                let line_text_right_trimmed = bun_core::trim_right(line_text_, b" \r\n\t");
-                let line_text = bun_core::trim_left(line_text_right_trimmed, b"\n\r");
-                if location.column > 0 && !line_text.is_empty() {
-                    let mut line_offset_for_second_line: usize =
-                        usize::try_from(location.column - 1).expect("int cast");
+                let line_text = bun_core::trim_left(line_text_, b"\n\r");
+                if location.column > 0 && !bun_core::trim_right(line_text, b" \r\n\t").is_empty() {
+                    let (line_text, caret_column) = excerpt_around_column(
+                        line_text,
+                        usize::try_from(location.column - 1).expect("int cast"),
+                        // A cut can drop the key that marks a secret, so a redacted line prints whole.
+                        if redact_sensitive_information {
+                            usize::MAX
+                        } else {
+                            MAX_EXCERPT_LEN
+                        },
+                    );
+                    let mut line_offset_for_second_line: usize = caret_column;
 
                     if location.line > -1 {
                         let bold = matches!(kind, Kind::Err | Kind::Warn);
@@ -1071,6 +1079,49 @@ fn write_n_bytes(to: &mut impl fmt::Write, b: u8, n: usize) -> fmt::Result {
     Ok(())
 }
 
+/// `Data::write_format` cuts a line longer than this many bytes, unless it redacts the line.
+const MAX_EXCERPT_LEN: usize = 120;
+/// The excerpt starts this many bytes before the caret, or earlier when the line ends first.
+const EXCERPT_LEN_BEFORE_CARET: usize = 40;
+
+/// Walks `text` for up to `columns` UTF-16 code units. Returns the bytes and the code units walked.
+fn advance_utf16_columns(text: &[u8], columns: usize) -> (usize, usize) {
+    use bun_core::strings::{CodepointIterator, Cursor};
+    let iter = CodepointIterator::init(text);
+    let mut cursor = Cursor::default();
+    let mut walked: usize = 0;
+    while walked < columns && iter.next(&mut cursor) {
+        walked += 1 + (cursor.c > 0xFFFF) as usize;
+    }
+    (cursor.i as usize + cursor.width as usize, walked)
+}
+
+/// The part of `line_text` to print for a caret at the 0-based `column`, and the caret's column in it.
+fn excerpt_around_column(line_text: &[u8], column: usize, max_len: usize) -> (&[u8], usize) {
+    debug_assert!(max_len >= EXCERPT_LEN_BEFORE_CARET);
+    let (caret, caret_column) = advance_utf16_columns(line_text, column);
+    let visible = bun_core::trim_right(line_text, b" \r\n\t");
+    if line_text.len() <= max_len {
+        return (visible, caret_column);
+    }
+    let caret = caret.min(visible.len());
+    let mut hi = (caret.saturating_sub(EXCERPT_LEN_BEFORE_CARET) + max_len).min(visible.len());
+    let mut lo = hi.saturating_sub(max_len);
+    // A UTF-8 sequence has at most 3 continuation bytes.
+    for _ in 0..3 {
+        if !bun_core::strings::is_on_char_boundary(visible, lo) {
+            lo -= 1;
+        }
+        if !bun_core::strings::is_on_char_boundary(visible, hi) {
+            hi += 1;
+        }
+    }
+    (
+        bun_core::trim_right(&visible[lo..hi], b" \r\n\t"),
+        advance_utf16_columns(&visible[lo..caret], usize::MAX).1,
+    )
+}
+
 // ───────────────────────────────────────────────────────────────────────────
 // BabyString
 // ───────────────────────────────────────────────────────────────────────────

test/cli/install/redacted-config-logs.test.ts

@@ -141,6 +141,53 @@ test("bunfig password value is masked in config error output", async () => {
   expect(coloredExit).toBe(1);
 });
 
+test("bunfig token is masked when its key is further from the error than one printed excerpt", async () => {
+  // The logger prints about 120 bytes around the caret of a long line. The
+  // `token` key is 154 bytes to the left of the caret here, and the redaction
+  // has to see that key to know that the string is a secret.
+  const secret = Buffer.alloc(143, "secretvalue").toString();
+  const masked = Buffer.alloc(143, "*").toString();
+  using dir = tempDir("redacted-bunfig-long-line", {
+    "bunfig.toml": `[install]\ntoken = "${secret}" ]\n`,
+    "package.json": "{}",
+  });
+
+  await using plain = Bun.spawn({
+    cmd: [bunExe(), "install"],
+    cwd: String(dir),
+    env: { ...bunEnv, NO_COLOR: "1" },
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+
+  const [plainOut, plainErr, plainExit] = await Promise.all([plain.stdout.text(), plain.stderr.text(), plain.exited]);
+
+  expect(plainOut).not.toContain("secretvalue");
+  expect(plainErr).not.toContain("secretvalue");
+  expect(plainErr).toContain(`2 | token = "${masked}" ]`);
+
+  await using colored = Bun.spawn({
+    cmd: [bunExe(), "install"],
+    cwd: String(dir),
+    env: { ...bunEnv, NO_COLOR: undefined, FORCE_COLOR: "1" },
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+
+  const [coloredOut, coloredErr, coloredExit] = await Promise.all([
+    colored.stdout.text(),
+    colored.stderr.text(),
+    colored.exited,
+  ]);
+
+  expect(coloredOut).not.toContain("secretvalue");
+  expect(coloredErr).not.toContain("secretvalue");
+  expect(coloredErr).toContain(`"${masked}"`);
+
+  expect(plainExit).toBe(1);
+  expect(coloredExit).toBe(1);
+});
+
 describe.concurrent("redact", async () => {
   const tests = [
     {

test/js/bun/transpiler/parse-error-column.test.ts

@@ -1,4 +1,4 @@
-import { expect, test } from "bun:test";
+import { describe, expect, test } from "bun:test";
 import { bunEnv, bunExe, tempDir } from "harness";
 import { join } from "node:path";
 
@@ -142,8 +142,8 @@ test.concurrent("long non-ASCII line's lineText window does not split a UTF-8 se
 });
 
 test.concurrent("CLI caret stays under the token for an error at the end of a long line", async () => {
-  // `write_format` offsets the caret by `column - 1` with no knowledge of any
-  // left-trim, so the window gate must not left-trim this case.
+  // The location keeps the whole 151-byte line. The printer shows its last 120
+  // bytes and indents the caret by what it printed, not by the column.
   using dir = tempDir("parse-col-caret", {
     "long.js": Buffer.alloc(150, "a").toString() + "]",
   });
@@ -158,5 +158,166 @@ test.concurrent("CLI caret stays under the token for an error at the end of a lo
   const lines = stderr.split("\n");
   const textLine = lines.find(l => l.includes("]"))!;
   const caretLine = lines.find(l => l.trimEnd().endsWith("^"))!;
-  expect({ token: textLine.indexOf("]"), caret: caretLine.indexOf("^") }).toEqual({ token: 154, caret: 154 });
+  expect({ token: textLine.indexOf("]"), caret: caretLine.indexOf("^") }).toEqual({ token: 123, caret: 123 });
+});
+
+const fill = (count: number, char: string) => Buffer.alloc(count, char).toString();
+
+/**
+ * Runs `bun <args>` in a directory holding `files`. Returns the exit code,
+ * stderr and every source excerpt in it: a `N | text` line and the index of
+ * the `^` under it.
+ */
+async function printedExcerpts(args: string[], files: Record<string, string>) {
+  using dir = tempDir("parse-col-excerpt", files);
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), ...args],
+    env: bunEnv,
+    cwd: String(dir),
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+  const [stderr, , exitCode] = await Promise.all([proc.stderr.text(), proc.stdout.text(), proc.exited]);
+  const lines = stderr.split(/\r?\n/);
+  const excerpts: { excerpt: string; caret: number }[] = [];
+  for (let i = 0; i + 1 < lines.length; i++) {
+    if (/^\d+ \| /.test(lines[i]) && /^ *\^$/.test(lines[i + 1])) {
+      excerpts.push({ excerpt: lines[i], caret: lines[i + 1].indexOf("^") });
+    }
+  }
+  return { stderr, excerpts, exitCode };
+}
+
+// The logger prints at most about 120 bytes of a line: 40 before the caret and
+// 80 after it, or the last 120 when the line ends sooner. It indents the caret
+// by what it printed. A location can hold far more than 120 bytes: the parsers
+// keep the whole line for an error in its last 80 bytes, and CSS always does.
+const longArray = "[" + fill(80_000, "1,") + "]";
+
+describe.each([["build"], ["run"]])("bun %s prints a bounded excerpt of a very long line", subcommand => {
+  test.concurrent("for an error at its start", async () => {
+    const source = `var b = (; var a = ${longArray};`;
+    const { stderr, excerpts, exitCode } = await printedExcerpts([subcommand, "long.js"], { "long.js": source });
+    expect(excerpts).toEqual([{ excerpt: "1 | " + source.slice(0, 9 + 80), caret: 4 + 9 }]);
+    expect(stderr.length).toBeLessThan(1024);
+    expect(exitCode).toBe(1);
+  });
+
+  test.concurrent("for an error in its middle", async () => {
+    const source = `var a = ${longArray}; var b = (; var c = ${longArray};`;
+    const at = source.indexOf("(;") + 1;
+    const { stderr, excerpts, exitCode } = await printedExcerpts([subcommand, "long.js"], { "long.js": source });
+    expect(excerpts.map(e => e.excerpt)).toEqual(["1 | " + source.slice(at - 40, at + 80)]);
+    // This location does not say how much of the line it dropped on the left,
+    // so only the length of the caret line is checked: it was `at` spaces long.
+    expect(excerpts[0].caret).toBeLessThanOrEqual(excerpts[0].excerpt.length);
+    expect(stderr.length).toBeLessThan(1024);
+    expect(exitCode).toBe(1);
+  });
+
+  test.concurrent("for an error at its end", async () => {
+    const source = `var a = ${longArray}; var b = (;`;
+    const { stderr, excerpts, exitCode } = await printedExcerpts([subcommand, "long.js"], { "long.js": source });
+    expect(excerpts).toEqual([{ excerpt: "1 | " + source.slice(-120), caret: 4 + 119 }]);
+    expect(stderr.length).toBeLessThan(1024);
+    expect(exitCode).toBe(1);
+  });
+});
+
+test.concurrent("an error in the trailing whitespace of a very long line prints the end of its text", async () => {
+  // "Unexpected end of file" at the last of 200 spaces. Those 200 bytes are
+  // not the excerpt, and the caret goes right after the `(`.
+  const text = `var a = ${longArray}; var b = (`;
+  const { stderr, excerpts, exitCode } = await printedExcerpts(["build", "long.js"], {
+    "long.js": text + fill(200, " "),
+  });
+  expect(excerpts).toEqual([{ excerpt: "1 | " + text.slice(-120), caret: 4 + 120 }]);
+  expect(stderr.length).toBeLessThan(1024);
+  expect(exitCode).toBe(1);
+});
+
+test.concurrent("an error in the trailing whitespace of a short line keeps its caret at the column", async () => {
+  const { excerpts, exitCode } = await printedExcerpts(["build", "short.js"], {
+    "short.js": "var b = (" + fill(20, " "),
+  });
+  expect(excerpts).toEqual([{ excerpt: "1 | var b = (", caret: 4 + 28 }]);
+  expect(exitCode).toBe(1);
+});
+
+test.concurrent("an error and its note on one very long line both print a bounded excerpt", async () => {
+  const source = `const x = 1; var a = ${longArray}; const x = 2;`;
+  const { stderr, excerpts, exitCode } = await printedExcerpts(["build", "long.js"], { "long.js": source });
+  expect(excerpts).toEqual([
+    { excerpt: "1 | " + source.slice(-120), caret: 4 + 120 - "x = 2;".length },
+    { excerpt: "1 | " + source.slice(0, 6 + 80), caret: 4 + 6 },
+  ]);
+  expect(stderr.length).toBeLessThan(1024);
+  expect(exitCode).toBe(1);
+});
+
+test.concurrent.each([
+  // The last 120 bytes start one byte into an `é` and three bytes into a `𐐀`.
+  ["2-byte", fill(600, "\u00E9") + "]", "1 | " + fill(120, "\u00E9") + "]", 4 + 60],
+  ["4-byte", fill(400, "\u{10400}") + "xy]", "1 | " + fill(120, "\u{10400}") + "xy]", 4 + 60 + 2],
+])(
+  "bounded excerpt of a line of %s characters starts on a character and counts UTF-16 units",
+  async (_, source, excerpt, caret) => {
+    const { excerpts, exitCode } = await printedExcerpts(["build", "long.js"], { "long.js": source });
+    expect(excerpts).toEqual([{ excerpt, caret }]);
+    expect(exitCode).toBe(1);
+  },
+);
+
+describe("bun build prints a bounded excerpt of a very long CSS line", () => {
+  // A stray `}` after a rule is an error at the `}`.
+  const rules = fill(60_000, "a{color:red}");
+
+  test.concurrent("for an error at its start", async () => {
+    const source = "a{color:red}}" + rules;
+    const { stderr, excerpts, exitCode } = await printedExcerpts(["build", "long.css"], { "long.css": source });
+    expect(excerpts).toEqual([{ excerpt: "1 | " + source.slice(0, 120), caret: 4 + 12 }]);
+    expect(stderr.length).toBeLessThan(1024);
+    expect(exitCode).toBe(1);
+  });
+
+  test.concurrent("for an error in its middle", async () => {
+    const source = rules + "}" + rules;
+    const { stderr, excerpts, exitCode } = await printedExcerpts(["build", "long.css"], { "long.css": source });
+    expect(excerpts).toEqual([{ excerpt: "1 | " + source.slice(60_000 - 40, 60_000 + 80), caret: 4 + 40 }]);
+    expect(stderr.length).toBeLessThan(1024);
+    expect(exitCode).toBe(1);
+  });
+
+  test.concurrent("for an error at its end", async () => {
+    // "Unexpected end of input": the caret is one column past the last `}`.
+    const source = rules + "}";
+    const { stderr, excerpts, exitCode } = await printedExcerpts(["build", "long.css"], { "long.css": source });
+    expect(excerpts).toEqual([{ excerpt: "1 | " + source.slice(-120), caret: 4 + 120 }]);
+    expect(stderr.length).toBeLessThan(1024);
+    expect(exitCode).toBe(1);
+  });
+});
+
+test.concurrent("bounded excerpt of a CSS line starts and ends on a character", async () => {
+  // 40 bytes before the stray `}` is one byte into a `€`, and 80 bytes after
+  // it is two bytes into one.
+  const comment = "/*" + fill(60_000, "\u20AC") + "*/";
+  const source = comment + "a{color:red}}" + comment + "a{color:red}";
+  const { stderr, excerpts, exitCode } = await printedExcerpts(["build", "long.css"], { "long.css": source });
+  expect(excerpts).toEqual([
+    {
+      excerpt: "1 | " + fill(27, "\u20AC") + "*/a{color:red}}/*" + fill(78, "\u20AC"),
+      caret: 4 + 9 + "*/a{color:red}".length,
+    },
+  ]);
+  expect(stderr.length).toBeLessThan(1024);
+  expect(exitCode).toBe(1);
+});
+
+test.concurrent("bun install prints a bounded excerpt of a one-line package.json that is cut short", async () => {
+  const source = `{"name":"x","version":"1.0.0","files":[` + fill(80_000, '"a",') + `"a"]`;
+  const { stderr, excerpts, exitCode } = await printedExcerpts(["install"], { "package.json": source });
+  expect(excerpts).toEqual([{ excerpt: "1 | " + source.slice(-120), caret: 4 + 119 }]);
+  expect(stderr.length).toBeLessThan(1024);
+  expect(exitCode).toBe(1);
 });