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bun:test: print a nested multi-line string, Map or Set on its key's line in failure messages #47748

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bun:test: print a nested multi-line string, Map or Set on its key's line in failure messages #47748

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bun:test: print a nested multi-line string, Map or Set on its key's l…
robobun Nov 2, 2026
ca3ad8d
ci: retrigger
robobun Nov 8, 2026
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45 changes: 37 additions & 8 deletions src/runtime/test_runner/pretty_format.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -772,6 +772,11 @@ impl<'w, W: bun_io::Write> WrappedWriter<'w, W> {
use bun_io::AsFmt;

impl<'a> Formatter<'a> {
/// Older versions stored these line breaks at every depth, so snapshots keep them. Only a failure message counts its output.
fn has_snapshot_line_breaks(&self) -> bool {
self.indent == 0 || self.output_length.is_none()
}

pub(crate) fn write_indent<W: bun_io::Write>(&self, writer: &mut W) -> bun_io::Result<()> {
let indent = self.indent.min(32);
let buf = [b' '; 64];
Expand Down Expand Up @@ -1156,6 +1161,7 @@ impl<'a> Formatter<'a> {
writer.write_all(b"String {}");
return Ok(());
}
let line_breaks = self.has_snapshot_line_breaks();
if self.indent == 0 && str.len > 0 {
writer.write_all(b"\n");
}
Expand All @@ -1176,8 +1182,14 @@ impl<'a> Formatter<'a> {
}
}
self.reset_line();
writer.write_all(b"}\n");
self.indent = self.indent.saturating_sub(1);
if line_breaks {
// In a snapshot the closing brace of a nested String object has no indentation.
writer.write_all(b"}\n");
} else {
let _ = self.write_indent(writer.ctx);
writer.write_all(b"}");
}
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return Ok(());
}

Expand All @@ -1193,7 +1205,7 @@ impl<'a> Formatter<'a> {

let mut has_newline = false;

if str.index_of_any(b"\n\r").is_some() {
if str.index_of_any(b"\n\r").is_some() && self.has_snapshot_line_breaks() {
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has_newline = true;
writer.write_all(b"\n");
}
Expand Down Expand Up @@ -1736,7 +1748,7 @@ impl<'a> Formatter<'a> {
writer.write_all(b"[native code]");
}
Tag::Promise => {
if self.good_time_for_a_new_line() {
if self.has_snapshot_line_breaks() && self.good_time_for_a_new_line() {
writer.write_all(b"\n");
let _ = self.write_indent(writer.ctx);
}
Expand Down Expand Up @@ -1791,7 +1803,12 @@ impl<'a> Formatter<'a> {
return Ok(());
}

writer.print(format_args!("\n{} {{\n", map_name));
let line_breaks = self.has_snapshot_line_breaks();
if line_breaks {
writer.print(format_args!("\n{} {{\n", map_name));
} else {
writer.print(format_args!("{} {{\n", map_name));
}
{
self.indent += 1;
// hoist global_this (Copy &ref) before iter mutably
Expand All @@ -1815,7 +1832,9 @@ impl<'a> Formatter<'a> {
}
let _ = self.write_indent(writer.ctx);
writer.write_all(b"}");
writer.write_all(b"\n");
if line_breaks {
writer.write_all(b"\n");
}
}
Tag::Set => {
let length_value = value
Expand All @@ -1830,7 +1849,11 @@ impl<'a> Formatter<'a> {
let prev_quote_strings = self.quote_strings;
self.quote_strings = true;

let _ = self.write_indent(writer.ctx);
let line_breaks = self.has_snapshot_line_breaks();
if line_breaks {
// A snapshot also has the indentation of a nested Set before its name.
let _ = self.write_indent(writer.ctx);
}

let set_name: &str =
if value.js_type() == JSType::WeakSet { "WeakSet" } else { "Set" };
Expand All @@ -1841,7 +1864,11 @@ impl<'a> Formatter<'a> {
return Ok(());
}

writer.print(format_args!("\n{} {{\n", set_name));
if line_breaks {
writer.print(format_args!("\n{} {{\n", set_name));
} else {
writer.print(format_args!("{} {{\n", set_name));
}
{
self.indent += 1;
let global = self.global_this;
Expand All @@ -1862,7 +1889,9 @@ impl<'a> Formatter<'a> {
}
let _ = self.write_indent(writer.ctx);
writer.write_all(b"}");
writer.write_all(b"\n");
if line_breaks {
writer.write_all(b"\n");
}
}
Tag::JSON => {
let str = value.json_stringify(self.global_this, self.indent)?;
Expand Down
6 changes: 6 additions & 0 deletions test/js/bun/test/expect-extend.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -731,6 +731,12 @@ describe("MatcherContext", () => {
expect(Bun.stripANSI(utils.diff(Symbol("a"), Symbol("b")))).toBe("Expected: Symbol(a)\nReceived: Symbol(b)");
});

test("diff prints a Set inside an object on the line of its key", () => {
expect(Bun.stripANSI(utils.diff({ s: new Set([1]) }, { s: new Set([2]) }))).toContain(
'\n "s": Set {\n- 1,\n+ 2,\n },\n',
);
});

test("diff rethrows an error thrown while printing a value", () => {
const thrown = new Error("from the trap");
const value = new Proxy(
Expand Down
15 changes: 15 additions & 0 deletions test/js/bun/test/printing/diffexample.fixture.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -355,3 +355,18 @@ test.skipIf(!Bun.enableANSIColors)("mix of whitespace-only and non-whitespace-on
`);
}
});

test("the output of a subprocess in an object", () => {
const received = { stdout: "hello\n", stderr: "warn: x\n", exitCode: 1 };
expect(received).toEqual({ stdout: "hello\n", stderr: "", exitCode: 0 });
});

test("a Set and a Map in an object", () => {
const received = { s: new Set([1, 2]), m: new Map([["a", 1]]), a: 1 };
expect(received).toEqual({ s: new Set([1, 3]), m: new Map([["a", 2]]), a: 1 });
});

test("a Set and a Map in an array", () => {
const received = [new Set([1, 2]), new Map([["a", 1]]), 1];
expect(received).toEqual([new Set([1, 3]), new Map([["a", 2]]), 1]);
});
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