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feat(console): split long messages for os_log and report errors as errors - #530
os_log silently truncates long messages with <…> at about 1 KB. console.error is logged at the default level, so log readers can't tell errors apart.
What is the new behavior?
Messages over 900 bytes are split (LogChunks.h), at line breaks when possible and never inside a UTF-8 sequence. Without the CLI's key below, each piece is a plain line with the console prefix repeated.
console.error and failed assertions use OS_LOG_TYPE_ERROR.
When the CLI writes "logFormat": 1 to the app's package.json and stdout is /dev/null, each piece is logged as [ns <id> <index>/<count>] <piece>. The id is unique per message in the process, and the pieces are exact slices of the message: only the first carries the console prefix. The CLI groups pieces by message id, prints a message as soon as its last piece arrives, and shows <…lost…> where pieces never arrived. It never joins the next message onto an unfinished one.
The unified log strips whitespace from the end of every entry, so a piece never ends in whitespace: the cut moves before it and the whitespace starts the next piece, after its header.
logFormat is the newest format the CLI understands. The runtime uses the lower of that and its own, so either side can add a format 2 later.
The key and the stdout check keep the headers to readers that understand them. Older CLIs never write the key, and an attached console fails the stdout check, so older CLIs and Xcode see plain split lines. The new CLI removes the headers when a device falls back to the syslog relay.
The runtime is prebuilt through SwiftPM, so a build setting can't reach it, and adding a build setting would relink. A package.json key costs only a re-sign.
Testing
The table below was run on the first version of this PR, which marked chunks with invisible characters. A demo app logged 11 messages (up to 100 KB, emoji, 800 lines, console.error, objects), compared exactly against the expected text on both launches of each run:
Setup
Simulator (iOS 26.2)
iPad (iPadOS 26.7)
New CLI, default / --log debug / --log trace
11/11
11/11
Published CLI 9.1.1
no markers, nothing lost, long messages stay split
same
Also confirmed with simctl launch --console-pty: markers stay off with a console attached. Launching from Xcode itself wasn't tested.
After the switch to logFormat (simulator only, iPhone 16 Pro, iOS 26.3):
The TestRunner suite passes: 1,835 tests, 0 failures.
30,000 random messages (UTF-8, line breaks, runs of spaces and tabs) split and join back exactly, with every entry's trailing whitespace stripped as the unified log does.
The test app, launched with stdout on /dev/null, logged 62 long messages from the main thread, two workers and forwarded stdout at the same time. Passing the captured log stream through the CLI's code rebuilt all 62 exactly, with no header left in the output. With an extra 2 MB message, all 61 checked messages still came through.
Not rerun on the iPad.
Known limit: in a probe with three threads logging while another logged 2 MB, about a third of the threads' chunks never reached the stream. Losses like that still happen, but pieces are now numbered, so the CLI shows <…lost…> where they belong instead of a silent gap. The 2 MB run above lost nothing, so that path is covered by the CLI's unit tests only.
Console messages and failed assertions are sent to the operating system’s logging service when available; errors are marked with error severity.
Long log messages are split into smaller chunks while preserving UTF-8 characters. When enabled in app configuration, markers indicate whether chunks continue the same line or start a new one.
When operating system logging is unavailable, messages continue to use the existing logging path.
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NativeScript/runtime/Helpers.h
NativeScript/runtime/Helpers.mm
NativeScript/runtime/LogChunks.h
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Walkthrough
The runtime adds a log chunking API and routes formatted messages through chunked OS logging. Chunk markers depend on app configuration and stdout. Console messages use OS logging with error severity for errors and failed assertions. Non-OS-logging paths remain available.
Adds a 900-byte recommended chunk size, break types, invisible markers, and ForEachLogChunk. The function prefers newline breaks and otherwise splits at UTF-8 boundaries. The Xcode project registers the header.
OS logging chunk writer NativeScript/runtime/Helpers.h, NativeScript/runtime/Helpers.mm
Formatted Objective-C and C messages use a chunked OS-log writer. The writer can append break markers. Marker use is enabled when logChunkMarkers is truthy and stdout refers to /dev/null; it is disabled when the application path is empty. Non-OS-logging fallbacks are unchanged.
A shared helper sends console messages to OS logging when enabled. It uses error severity for errors and failed assertions, and preserves the formatted level prefix for regular console messages.
sequenceDiagram
participant FormatPath
participant TNS_WriteToOsLog
participant ShouldMarkLogChunks
participant ForEachLogChunk
participant os_log
FormatPath->>TNS_WriteToOsLog: formatted message and prefix
TNS_WriteToOsLog->>ShouldMarkLogChunks: check marker setting
ShouldMarkLogChunks-->>TNS_WriteToOsLog: marker enabled or disabled
TNS_WriteToOsLog->>ForEachLogChunk: message and chunk limit
loop Each chunk
ForEachLogChunk-->>TNS_WriteToOsLog: chunk and break type
TNS_WriteToOsLog->>os_log: prefixed chunk and optional marker
end
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Suggested reviewers:nathanwalker
Merge Risk: Minimal · previous review db9ca
This change splits long log messages and reports console errors at error severity. No actionable merge-blocking risk remains in the reviewed code. The author's stated limit of dropped chunks under heavy concurrent logging is an accepted tradeoff.
Pre-merge checks: 4 · 1
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Docstring Coverage
Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documenta…
Write docstrings for the functions missing them to satisfy the coverage threshold.
Passed checks: 4 passed
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The title clearly and concisely describes the two main changes: splitting long messages for os_log and reporting errors with error severity.
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Full details: Docstring Coverage
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Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 6 functions across 3 files. (1 skipped: 1 unsupported.)
Resolution
Write docstrings for the functions missing them to satisfy the coverage threshold.
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Review comments at @NativeScript/runtime/Helpers.mm:
- Around line 511-512: Update the logChunkMarkers check to accept only NSNumber
values before calling boolValue; treat null and all other value types as
disabled, while preserving the IsDevNull(STDOUT_FILENO) condition.
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NativeScript/runtime/Console.cpp
NativeScript/runtime/Helpers.h
NativeScript/runtime/Helpers.mm
NativeScript/runtime/LogChunks.h
v8ios.xcodeproj/project.pbxproj
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…rors
os_log truncates messages at about 1 KB. They now go out as chunks of at most 900 bytes, cut at line breaks where possible and never inside a UTF-8 sequence. console.error uses OS_LOG_TYPE_ERROR.
When the CLI writes logChunkMarkers to the app's package.json and stdout is /dev/null, each chunk ends with an invisible marker that lets the CLI rebuild the original message. Other readers see plain split lines: older CLIs never set the key, and an attached console fails the stdout check.
Replaces the invisible end-of-chunk markers and the logChunkMarkers key.
When a message has to be split and the app's package.json has a logFormat
of 1 or more (with stdout going to /dev/null, as when the CLI launches the
app), each piece is logged as "[ns <id> <index>/<count>] <piece>". The id
is unique per message in the process. The pieces are consecutive slices of
the message and only the first carries the console prefix, so they join
back as they are. The unified log strips whitespace from the end of every
entry, so a piece never ends in whitespace: the cut moves before it and the
whitespace starts the next piece, behind its header.
With the id, index and count, the CLI can tell pieces apart by message
instead of by thread, notice a lost piece instead of joining the next
message onto an unfinished one, and print a message as soon as its last
piece arrives. logFormat holds the newest format the CLI understands; the
runtime uses the lower of that and its own.
Without the key, split messages are logged as before: plain lines, each
with the prefix repeated.
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What is the current behavior?
os_logsilently truncates long messages with<…>at about 1 KB.console.erroris logged at the default level, so log readers can't tell errors apart.What is the new behavior?
LogChunks.h), at line breaks when possible and never inside a UTF-8 sequence. Without the CLI's key below, each piece is a plain line with the console prefix repeated.console.errorand failed assertions useOS_LOG_TYPE_ERROR."logFormat": 1to the app'spackage.jsonand stdout is/dev/null, each piece is logged as[ns <id> <index>/<count>] <piece>. The id is unique per message in the process, and the pieces are exact slices of the message: only the first carries the console prefix. The CLI groups pieces by message id, prints a message as soon as its last piece arrives, and shows<…lost…>where pieces never arrived. It never joins the next message onto an unfinished one.logFormatis the newest format the CLI understands. The runtime uses the lower of that and its own, so either side can add a format 2 later.The key and the stdout check keep the headers to readers that understand them. Older CLIs never write the key, and an attached console fails the stdout check, so older CLIs and Xcode see plain split lines. The new CLI removes the headers when a device falls back to the syslog relay.
The runtime is prebuilt through SwiftPM, so a build setting can't reach it, and adding a build setting would relink. A
package.jsonkey costs only a re-sign.Testing
The table below was run on the first version of this PR, which marked chunks with invisible characters. A demo app logged 11 messages (up to 100 KB, emoji, 800 lines,
console.error, objects), compared exactly against the expected text on both launches of each run:--log debug/--log traceAlso confirmed with
simctl launch --console-pty: markers stay off with a console attached. Launching from Xcode itself wasn't tested.After the switch to
logFormat(simulator only, iPhone 16 Pro, iOS 26.3):/dev/null, logged 62 long messages from the main thread, two workers and forwarded stdout at the same time. Passing the capturedlog streamthrough the CLI's code rebuilt all 62 exactly, with no header left in the output. With an extra 2 MB message, all 61 checked messages still came through.Known limit: in a probe with three threads logging while another logged 2 MB, about a third of the threads' chunks never reached the stream. Losses like that still happen, but pieces are now numbered, so the CLI shows
<…lost…>where they belong instead of a silent gap. The 2 MB run above lost nothing, so that path is covered by the CLI's unit tests only.Part of a stack
Next: #532. The CLI side is NativeScript/nativescript-cli#6179.
Summary by CodeRabbit