inno-setupdirectivepreprocessor

What is the point of the #emit directive in Inno Setup?

Here are examples from the #emit directive documentation:

[Files]
#emit 'Source: "file1.ext"; DestDir: {' + MyDestDir + '}'
Source: "file2.ext"; DestDir: {#MyDestDir}
#emit GenerateVisualCppFilesEntries ; user defined function

In the first line I don't understand the DestDir part. Looks like the # symbol is missing there.

I understand the second line. But why do we need to use the #emit directive like in line 1 anyway?

Solution

  • Inno Setup preprocessor directives can be invoked using two syntaxes.

    A basic syntax:

    #directive params

    And an inline syntax:

    {#directive params}

    On top of that, the #emit directive is the default inline directive, assumed, when no explicit directive name is specified.

    So these three are equivalent:

    #emit MyDestDir

    {#emit MyDestDir}

    {#MyDestDir}

    Though the first does not make sense with a path variable, as it would result in invalid script syntax – but it can be used with a variable that contains a valid script syntax:

    #define FileSectionEntry 'Source: ' + MySource + '; DestDir: ' + MyDestDir
#emit FileSectionEntry

    While the other two inline examples can make sense, but only with other code on the same line, like in the code from your question:

    Source: "file2.ext"; DestDir: {#MyDestDir}

    Additionally an #emit with a (string) constant is basically pointless, as you can achieve the same without preprocessor.

    These three are equivalent:

    Source: "file2.ext"; DestDir: "{app}"

    #emit 'Source: "file2.ext"; DestDir: "{app}"'

    {#'Source: "file2.ext"; DestDir: "{app}"'}

    So getting back to the code in your script, these are (almost) equivalent:

    #emit 'Source: "file1.ext"; DestDir: {' + MyDestDir + '}'

    Source: "file1.ext"; DestDir: {#MyDestDir}

    The only problem is that I believe the curly brackets in the first line should not be there. The line should be:

    #emit 'Source: "file1.ext"; DestDir: ' + MyDestDir

    I have submitted a fix for this. It's basically another copy of the typo from your previous question: Why is there an additional pair of curly braces on the Inno Setup Preprocessor:#emit page?