Fix CONFIG REWRITE append duplicate newlines

[enjoy-binbin]

In the old code, everytime we perform a config rewrite, an
additional newline is appended, see #1396

Because iostream::eof will only return true after reading the
end of the stream. It does not indicate, that the next read will
be the end of the stream.

So everytime config rewrite is performed, the old loop will
append a newline in lines, and then we will append it to the
conf file.

In addition, the same modification has been made to other similar
places. This PR fixes #1396

[enjoy-binbin]

I tested it locally (with the CONFIG REWRITE)
and the ref: https://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-i-e-while-stream-eof-cons

[git-hulk]

@enjoy-binbin Thanks for your efforts. ❤️

[torwig]

LGTM

[PragmaTwice]

Thanks for your patch, but seems changes are required.

[PragmaTwice]

Here is a simple test to demonstrate this point:

❯ cat y.cpp
#include <fstream>
#include <iostream>
#include <string>

int main() {
std::ifstream file("hello.txt");
std::string line;
while (std::getline(file, line)) {
    if (file.eof()) break;
    std::cout << "> " << line << std::endl;
}
}

❯ python -c "file=open('hello.txt', 'w');file.write('a\nb\nc');file.close()"

❯ cat hello.txt
a
b
c%

❯ ./y
> a
> b

❯

[enjoy-binbin]

@PragmaTwice thanks for the detailed explanation! do you have any suggestions? i may need some time to figure it out
do you think if i put the if (file.eof()) break; in the last will help?

[PragmaTwice]

@PragmaTwice thanks for the detailed explanation! do you have any suggestions? i may need some time to figure it out do you think if i put the if (file.eof()) break; in the last will help?

Not sure the eof check is necessary, maybe something like while(file.good() && getline(...)) is ok.

The call to getline will return the stream itself, so operator bool of the stream is called, and it is equal to !stream.fail().

[enjoy-binbin]

i change to use while(file.good() && getline(...)) for now, i also tested it in local, it is fine

[git-hulk]

Thanks all, merging...