Fix a method to split SmartREST messages and improve failure reason

[rina23q]

Proposed changes

When receiving multiline SmartREST messages, splitting simply by \n is not a right approach because a SmartREST message can also contain \n, e.g. an argument of c8y_Command.

Also, in case of an operation failure, giving only the last line of stderr is not easy enough for users to understand why the operation failed. It should give also the whole context as much as possible.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

#1687

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s)
• I ran cargo fmt as mentioned in CODING_GUIDELINES
• I used cargo clippy as mentioned in CODING_GUIDELINES
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

[reubenmiller]

Case 1: Quotes are ignored on multiline commands if the line ends with a quote

There seems to be an issue when handling the newline split logic and double quotes. I have a suspicion it is swallowing the last character (or the last character is just being forgotten)

For example if you take a multiline command, if a line ends in a double quote (") then a newline, the last character does not get passed to the plugin. If a space is added to the end of the line (before the newline char), then it magically works. So it is very likely just a small logical error when processing the characters.

Works (with a dummy trailing space at the end of the first line, after the closing double quote)

echo "testme" 
echo "test again"

Does not work (no trailing space on the first line)

echo "testme"
echo "test again"

Case 2: Commas cause the command to be truncated

If a comma occurs on another line, then only the lines up until the line with the comma is sent to the plugin.

For example the following command (which should produce 3 lines on the stdout, only returns the first 2)
Command

echo "line 1";
echo "line 2";
echo "line, 3";

Output

line 1
line 2

Where as the expected output is:

line 1
line 2
line, 3

[didier-wenzek]

Approved

[reubenmiller]

Approved

[reubenmiller]

Case 1: Quotes are ignored on multiline commands if the line ends with a quote

There seems to be an issue when handling the newline split logic and double quotes. I have a suspicion it is swallowing the last character (or the last character is just being forgotten)

For example if you take a multiline command, if a line ends in a double quote (") then a newline, the last character does not get passed to the plugin. If a space is added to the end of the line (before the newline char), then it magically works. So it is very likely just a small logical error when processing the characters.

Works (with a dummy trailing space at the end of the first line, after the closing double quote)

echo "testme" 
echo "test again"

Does not work (no trailing space on the first line)

echo "testme"
echo "test again"

Case 2: Commas cause the command to be truncated

If a comma occurs on another line, then only the lines up until the line with the comma is sent to the plugin.

For example the following command (which should produce 3 lines on the stdout, only returns the first 2) Command

echo "line 1";
echo "line 2";
echo "line, 3";

Output

line 1
line 2

Where as the expected output is:

line 1
line 2
line, 3

We found the root cause and it was the shell handler script which was causing the errors. The example in the ticket has also been updated, #1687