Regex replace multilines in powershell - regex

Question

I want to replace these line in my AssemblyInfo.cs encoded in UTF-8 with Windows CRLF at the end of each lines
<<<<<<< HEAD
[assembly: AssemblyVersion("2.0.0.0")]
[assembly: AssemblyFileVersion("2.0.0.0")]
=======
[assembly: AssemblyVersion("1.1.0.0")]
[assembly: AssemblyFileVersion("1.1.0.0")]
>>>>>>> v1_final_release
by these
[assembly: AssemblyVersion("2.0.0.0")]
[assembly: AssemblyFileVersion("2.0.0.0")]
To do so, I have a powershell script that will parse through all my files and do the replacement.
The regex I prepare in regex101 is this one and works on 101 :
<<<<<<<\sHEAD\n\[assembly:\sAssemblyVersion\("2\.0\.0\.0"\)\]\n\[assembly:\sAssemblyFileVersion\("2\.0\.0\.0"\)\]\n=======\n\[assembly:\sAssemblyVersion\("1\.1\.0\.0"\)\]\n\[assembly: AssemblyFileVersion\("1\.1\.0\.0"\)\]\n>>>>>>>\sv1_final_release
I can't manage to make the -replace work on the new lines.
But when targeting only <<<<<<<\sHEAD, it matches and replacing is performed.
All the following variations failed :
<<<<<<<\sHEAD\n\[assembly: no error no replacement
<<<<<<<\sHEAD\r\n\[assembly: no error no replacement
<<<<<<<\sHEADrn\[assembly: no error no replacement, write-host prints it as
<<<<<<<\sHEAD
\[assembly:
It's not about /gm or (*CRLF)
My powershell instruction for info :
$ConflictVersionRegex = "<<<<<<<\sHEAD\n\[assembly:\sAssemblyVersion\(`"2\.0\.0\.0`"\)\]\n\[assembly:\sAssemblyFileVersion\(`"2\.0\.0\.0`"\)\]\n=======\n\[assembly:\sAssemblyVersion\(`"1\.1\.0\.0`"\)\]\n\[assembly: AssemblyFileVersion\(`"1\.1\.0\.0`"\)\]\n>>>>>>>\sv1_final_release"
$ConflictVersionRegexTest = "<<<<<<<\sHEAD`r`n\[assembly:"
$fileContent = Get-Content($filePath)
$filecontent = $filecontent -replace $ConflictVersionRegexTest, $AssemblyNewVersion
[System.IO.File]::WriteAllLines($filePath, $fileContent, $Utf8NoBomEncoding)
What am I missing ? Why is it not replacing ?
Many thanks

Answer 1

Based on feedback from Poutrathor (the OP), there were two problems:
The primary problem was that Get-Content($filePath) (which should be written asGet-Content $filePath[1]) reads the file line by line, which results in an array of lines when captured in a variable.
-replace then operates on each input line individually, which means that the line-spanning regex won't match anything.
Solution: Use Get-Content -Raw (PSv3+) to read the file as a whole into a single, multi-line string.
Secondarily, you mention needing to replace the regex newline (end-of-line) escape sequence (\n) (LF) with its PowerShell string-interpolation counterpart (`n) - note that PowerShell uses `, the backtick, as the escape character:
Note that that is only necessary in the replacement string, in order to create actual, literal newlines (line breaks) on output - as opposed to using regex construct \n for matching newlines.
However, on Windows, newlines are typically CRLF sequences, i.e., a CR (\r, `r) immediately followed by a LF (\n / `n) - i.e., \r\n/ `r`n - whereas on Unix-like platforms they are just LF, \n / `n.
If you're not sure which style of newlines given input has, use \r?\n to match newlines in a cross-platform-compatible manner.
If you don't care what specific newlines the input has, this is safe to use methodically, as a matter of habit.
Therefore:
In your regex, while in your case you can choose between \r\n and `r`n, note that:
`r`n only works in double-quoted "..." strings.
It is generally preferable to use literal, single-quoted strings to store regexes - which requires use of \r\n (Windows) / \n (Unix) / \r?\n (platform-agnostic) - so that there's no confusion over which parts of the string PowerShell interpolates up front vs. which parts are interpreted by the regex engine.
In your replacement string, use `r`n inside "..." to create actual newlines.
As an alternative to using escape sequences to represent newlines, you can use here-strings to conveniently define multi-line strings with actual newlines (line breaks), as shown in Paweł Dyl's answer, but there's a caveat:
Here-strings invariably have the same style of newline as the enclosing script file, which means that:
A regex based on a here-string will only match if the input happens to have the same style of newlines as the script file.
A replacement string based on a here-string will invariably use the script file's newline style.
[1] Your call looks like a .NET method call and while it happens to work in this case, such syntax confusion should be avoided: PowerShell cmdlets and functions are invoked like shell commands: without parentheses ((...)) and with whitespace-separated arguments.

Answer 2

See following demo:
$newText = #'
[assembly: AssemblyVersion("2.0.0.0")]
[assembly: AssemblyFileVersion("2.0.0.0")]
'#
$src = #'
<<<<<<< HEAD
[assembly: AssemblyVersion("2.0.0.0")]
[assembly: AssemblyFileVersion("2.0.0.0")]
=======
[assembly: AssemblyVersion("1.1.0.0")]
[assembly: AssemblyFileVersion("1.1.0.0")]
>>>>>>> v1_final_release
Other lines and second instance
<<<<<<< HEAD
[assembly: AssemblyVersion("2.0.0.0")]
[assembly: AssemblyFileVersion("2.0.0.0")]
=======
[assembly: AssemblyVersion("1.1.0.0")]
[assembly: AssemblyFileVersion("1.1.0.0")]
>>>>>>> v1_final_release
Some other lines
'#
$src -replace ('<<<<<<< HEAD\s+',
'\[assembly: AssemblyVersion\("2\.0\.0\.0"\)\]\s+',
'\[assembly: AssemblyFileVersion\("2\.0\.0\.0"\)\]\s+'+
'=======\s+'+
'\[assembly: AssemblyVersion\("1\.1\.0\.0"\)\]\s+',
'\[assembly: AssemblyFileVersion\("1\.1\.0\.0"\)\]\s+'+
'>>>>>>> v1_final_release'),$newText
Also, make sure your contents are read as one large string. This can be achieved using Get-Content $path -Raw or [System.IO.File]::ReadAllText($path).