I am trying to create a util for logging.
I need to know the actual differences between print() vs debugPrint() and log().
Many answers I have seen are outdated or confusing. Also, some upvoted answers are contradict.
I am trying to print error messages in red color. I am using ANSI code to achieve it.
debugPrint("\x1B[31m HelloDebug \x1B[0m");
The above one print in red color.
But when i do the same using log(), its not printing in red color. Its escaping the ANSI code.
One thing I found out was log() has error parameter.
If i pass something as error , it handles red color by default.
Here in the first one using log, red is not coming because ANSI code is ignored. But in debugPrint using it's working fine. In third one it takes error red by default. But extra line is added even for empty string message.
Code:
Output:
Is it possible use ANSI code for making color text using log?
Because I have other ANSI code to make different color text.
I dont want use debugPrint because if I print some thing too frequently , the system ignore the logs.
After digging some time I found out that log function is implemented in c++ in the dart runtime.As the log function is external function in dart sdk.
external void log(
String message, {
DateTime? time,
int? sequenceNumber,
int level = 0,
String name = '',
Zone? zone,
Object? error,
StackTrace? stackTrace,
});
https://github.com/dart-lang/sdk/blob/main/runtime/lib/developer.cc
Also I see some different answers while digging.
The below answer says debugPrint only available inside widget class. Is it still true?
https://stackoverflow.com/a/52241553/9248098
EDIT:
While using debugPrint and when I launch app from Android studio terminal, the ANSI color is working in android but when I run it same in iOS its escaping the characters in same Android Studio terminal.
If ANSI code support is based on terminal support, I couldn't figure out why its having issue in same terminal in iOS.
It is well explained in this page Debugging Flutter apps programmatically
debugPrint() is similar to print() but with a throttles applied to prevents being dropped by Android’s kernel.
If you have linter setup on VSCode or other IDE, you will see this warning whenever you use print in your code. For more information, you can refer to Avoid print calls in production code.
To avoid the lint error, you can use kDebugMode with print or debugPrint instead.
if (kDebugMode) {
print('test print');
}
// OR
debugPrint('test debugPrint');
As for log(), it actually allows you to include more information on the logging output. For example, you can add the runtimeType and the relevant object in the log that can help you in debugging the code.
log(
'test log',
name: runtimeType.toString(),
error: myObj,
);
** btw I tried log with ANSI code log("\x1B[31m HelloDebug \x1B[0m");, it is working as expected.
Related
I just cannot figure out how to show logging messages when running dart files from terminal.
Example example.dart:
import 'dart:developer';
void main() {
print('print');
log('log');
}
Expected output:
print
log
Actual output:
print
I tried calling dart example.dart, dart run --all example.dart, dart run --verbosity=all example.dart, and different values instead of all (info, ...).
But non of these produced any helpful error messages let alone the out print I expect.
APIs from dart:developer (such as log) are intended to interact with debugging tools:
Interact with developer tools such as the debugger and inspector.
It's not explicit from the documentation for log, but I'd expect it to send a log message only to an attached debugger, not to the console.
If you want logging output that is independent of a debugger, use package:logging and add a listener that calls print, as shown by the example.
I'm trying to send a post request within dart with the following code.
Future<Response> post (url,
{
headers, // My Map<String, String> for header info
body // My Map<String, String> for body info
})
return JSON.jsonDecode(post);
I expect it to send, however, I get two errors.
The name response isn't a type, and cant be used as a type argument, when I hover over "Response" and
expected to find ;, when I hover over "post".
I also get green underlining in android studio saying avoid unnecessary statements
This problem happens in Computers with low specs which makes android studio take time to recognize new input. Waiting will fix the issue, and you can speed this "recognition" process by clicking on the type Response in you case which will make the editor focus on it. And also add parenthesis and commas in correct way before adding new code as Dart Analyzer will quickly get confused and fill your editor with error messages.
I encountered the same issue, and I found that rerunning flutter pub get helped as that command makes sure the Http library gets downloaded.
Does DART support predefined macros such as:
__LINE__
or
__FUNCTION__
The reason for asking is that the transformer DART2JS makes the console log not useful as all the logs shows: js_primitives.dart:30
[update BasE]
When using the transformer dart2js, print("hello world"); will result in:
JS('void', r'console.log(#)', "hello world);
to be invoked from function: printString(String string)
residing in the library dart2js._js_primitives
This results that the console.log message always contains the same line number over and over again wherever in the DART code a print(); is used. (As console.log will add automatically the filename and line-number to the console display of the wrapper function residing in dart2js._js_primitives)
As the current implementation of adding file-name and line-number to the console.log message is useless, it would have been nice if there would be another method that allows to display additional information.
As example, print("hello world" __FUNCTION__ __LINE__); would result in additional debug information that can be more useful.
You could use
void main() {
print(StackTrace.current);
}
to get better information about the source of the error
DartPad example
You can also run your code in a custom zone and define a custom print method for that zone. See also https://api.dartlang.org/stable/1.24.3/dart-async/Zone/print.html
Seems what you are looking for is source maps that dart2js creates, that contain the information needed to recreate line numbers in original dart files, from the javascript locations.
In a mozille extension I run:
SecSess.Logger.info("ctypes test");
Components.utils.import("resource://gre/modules/ctypes.jsm");
SecSess.Logger.info("1");
this.lib = ctypes.open("libcrypto.so");
SecSess.Logger.info("2");
var a = new Uint8Array(1<<10);
SecSess.Logger.info("3");
var ptr = new ctypes.uint8_t.ptr(a.buffer);
SecSess.Logger.info("4");
Why this ugly logging after each step you might ask? Well this code fails without showing me an error. (or at least I can't find the error message)
This is printed:
ctypes test
1
2
3
So the 5th log message is never printed which means the following statement never completes:
var ptr = new ctypes.uint8_t.ptr(a.buffer);
This is a simplified version of some old code I have to work with and which I also found online as being valid. However it doesn't work. This add-on wasn't developped using the new SDK with jpm. Quite frankly I don't know how and when it was developped but I need to run some tests on it. It comes with a few source files ordered in a components and a modules directory and a chrome.manifest and install.rdf in the root. I copied these files to the extension directory of Mozilla in order for it to work. The extension executes but there seems to be a problem with ctypes. Aren't ctypes fully supported anymore or are these old style add-on no longer valid for the modern Firefox?
Regards,
Roel
I think they landed a a patch to disallow making a pointer from buffers. I'll double check.
Edit:
Ah per this: https://developer.mozilla.org/en-US/docs/Mozilla/js-ctypes/Using_js-ctypes/Working_with_ArrayBuffers, you don't have to wrap it with a ctypes.uint8_t.ptr just pass it like a.buffer to wherever you need it. :)
Do any editors honer C #line directives with regards to goto line features?
Context:
I'm working on a code generator and need to jump to a line of the output but the line is specified relative to the the #line directives I'm adding.
I can drop them but then finding the input line is even a worse pain
If the editor is scriptable it should be possible to write a script to do the navigation. There might even be a Vim or Emacs script that already does something similar.
FWIW when I writing a lot of Bison/Flexx I wrote a Zeus Lua macro script that attempted to do something similar (i.e. move from input file to the corresponding line of the output file by search for the #line marker).
For any one that might be interested here is that particular macro script.
#line directives are normally inserted by the precompiler, not into source code, so editors won't usually honor that if the file extension is .c.
However, the normal file extension for post-compiled files is .i or .gch, so you might try using that and see what happens.
I've used the following in a header file occasionally to produce clickable items in
the VC6 and recent VS(2003+) compiler ouptut window.
Basically, this exploits the fact that items output in the compiler output
are essentially being parsed for "PATH(LINENUM): message".
This presumes on the Microsoft compiler's treatment of "pragma remind".
This isn't quite exactly what you asked... but it might be generally helpful
in arriving at something you can get the compiler to emit that some editors might honor.
// The following definitions will allow you to insert
// clickable items in the output stream of the Microsoft compiler.
// The error and warning variants will be reported by the
// IDE as actual warnings and errors... which means you can make
// them occur in the task list.
// In theory, the coding standards could be checked to some extent
// in this way and reminders that show up as warnings or even
// errors inserted...
#define strify0(X) #X
#define strify(X) strify0(X)
#define remind(S) message(__FILE__ "(" strify( __LINE__ ) ") : " S)
// example usage
#pragma remind("warning: fake warning")
#pragma remind("error: fake error")
I haven't tried it in a while but it should still work.
Use sed or a similar tool to translate the #lines to something else not interpreted by the compiler, so you get C error messages on the real line, but have a reference to the original input file nearby.