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THIS INFORMATION IS NOW MAINTAINED IN THE TOOLS --help output (Since this is a private repository users cannot read this page)
The Catalog Preview --migration options performs the following migration checks:
In Puppet 4.x. an empty String is considered to be true, while it was false in Puppet 3.x. This migration check logs a warning with the issue code MIGRATE4_EMPTY_STRING_TRUE whenever an empty string is evaluated in a context where it matters if it is true or false. This means that you will not see warnings for all empty strings, just those that are used to make decisions.
To fix these warnings, review the logic and consider the case of undef not being the same as an empty string, and that empty strings are true.
In Puppet 4.x all bare words that start with an upper case letter is a reference to a Type (Data Type such as Integer, String, or Array, or a Resource Type such as File, or User). In Puppet 3.x such upper case bare words were considered to be string values, and only when appearing in certain locations would they be interpreted as a reference to a type. The migration checker issues a warning for all upper case bare words that are used in comparisons ==, >, <, >=, <=, matches =~ and !~, and when used as case or selector options.
To fix these warnings, quote the upper case bare word if a string is intended, (or alter the logic to use the type system in the unlikely event that the .3x. code did something in relation to resource type name processing).
In 4.x, comparison of String and Number is different than in 3.x.
'1' == 1 # 4x. false, 3x. true
'1' <= 1 # 4x. error, 3x. true
The migration checker logs a warning with the issue code MIGRATE4_EQUALITY_TYPE_MISMATCH when a String and a Number are checked for equality.
To fix this, decide if values are best represented as strings or numbers. To convert a string to a number simply add 0 to it. To convert a number to a string, either interpolate it; "$x" (to convert it to a decimal number), or use the sprintf function to convert it to octal, hex or a floating point notation. The sprintf function has many options that control the string representation, upper/lower case letters in hex numbers, prefix 0x, 0X, the precision of a floating point representation etc.
Also consider if input should be a string or a number - that is a better fix than sprinkling data type conversions all over the code.
In 4.x, case and selector options are matched differently than in 3.x. In 3.x if the match was not true, the match would be made with the operands converted to strings. This means that 4.x logic can select a different (or no option) given the same input.
The migration checker logs a warning with the issue code MIGRATE4_OPTION_TYPE_MISMATCH for every evaluated option that did not match because of a difference in type.
The fix for this depends on what the types of the test and option expressions are - most likely number vs. string mismatch, and then the fix is the same as for MIGRATE4_EQUALITY_TYPE_MISMATCH. For other type mismatches review the logic for what was intended and make adjustments accordingly.
This migration check helps with unquoted numbers where strings are intended.
A common construct is to use values like '01', '02' for ordering of resources. It is also a common mistake to enter them as bare word numbers e.g. 01, 02. The difference between 3.x and 4.x is that 3.x treats all bare word numbers as strings (unless arithmetic is performed on them which produces numbers), whereas 4.x treats numbers as numbers from the start. The consequence in manifests using ordering is that 1, 100, 1000 comes before 2, 200, and 2000 because the ordering converts the numbers back to strings without the leading zero.
In 4.x. the leading zero means that the value is an octal number.
The migration checker logs a warning for every occurrence of octal, and hex numbers with the issue code MIGRATE4_AMBIGOUS_NUMBER in order to be able to find all places where the value is used for ordering.
To fix these issues, review each occurrence and quote the values that represent "ordering", or file mode (since file mode is a string value in 4.x).
In 4.x. a white space between a value and a `[´ means that the ´[´ signals the start of an Array instead of being the start of an "at-index/key" operation. In 3.x. white space is not significant. Most such places will lead to errors, but there are corner cases - like in the example below
if true {
$a = File ['foo']
}
Here 4.x will assign File (a resource type) to $a and then produce an array containing the string 'foo'.
The migration checker logs a warning with the issue code MIGRATE4_ARRAY_LAST_IN_BLOCK for such occurences.
To fix this, simply remove the white space.