False positive "undefined variable" error when compiling SCSS

Getting an error message when compiling my SCSS using the ruby compass gem.

run: /var/lib/gems/1.8/gems/compass-0.12.2/bin/compass compile
out: unchanged sass/partial/grid.scss
out:     error sass/partial/catalog.scss (Line 5: Undefined variable: "$paragraphFont".)
out:    create css/generated/partial/catalog.css 
out:    create css/generated/partial/base.css 
out: overwrite css/generated/screen.css

My screen.scss imports partials like this:

@import "partial/base";
@import "partial/catalog";

In my base partial I have the $paragraphFont defined.

$paragraphFont: 'Lucida Sans', arial;
$regularFontSize: 14px;

And in catalog.scss I use it:

.product-view #price-block {
    p {
        font-weight: normal;
        font-family: $paragraphFont;
        ....
    }
}

Weird thing is that the css gets compiled just fine, and the $paragraphFont is populated correctly. So I don't know why the compiler is complaining at me about an error.

You're generating files that don't need to be generated.

• screen.scss -> screen.css
• base.scss -> base.css
• catalog.scss -> catalog.css

The catalog file is being compiled on its own. Since it is not importing base.scss, the variables are not set. Your screen.scss file generates as you expect because it is importing all of the necessary information.

What you want to do is rename your partials to begin with an underscore to prevent them from being compiled on their own:

• screen.scss -> screen.css
• _base.scss (not compiled)
• _catalog.scss (not compiled)

A simpler explanation that probably fits most of the users here:

You're compiling all your sass, when you only need to compile the top level file

sass is commonly modularised as follows:

toplevel.scss
  include child1.scss
  include child2.scss (that also uses variables from child1.sass but does not import child1.scss)
  include child3.scss (that also uses variables from child1.sass but does not import child1.sass)

When compiling, you only need to compile toplevel.scss. Compiling other files on their own (eg, child2.scss) will generate errors about undefined variables.

In your gulpfile:

gulp.task('sass', function () {
  gulp
    .src('./static/scss/toplevel.scss') // NOT *.scss
    .pipe(sass())
    // Rest is just decoration
    .pipe(prefixer('last 2 versions', 'ie 9'))
    .pipe(gulp.dest('./static/css/dist'))
    .pipe(livereload(livereloadServer));
});

In your compass log it states:

A)  create css/generated/partial/catalog.css 
B)  create css/generated/partial/base.css

These need to be:

A)  create css/generated/partial/base.css
B)  create css/generated/partial/catalog.css 

My guess is that your screen.scss has incorrect import statements.

I'd recommend looking into common Sass directory organizational structures. My personal favorite is The 7-1 Pattern.

The nature of it splits commonly used elements into other files, which are all imported by a main.scss to kill redundancies.

But also, firstly pay attention to @cimmanon's answer, as he more directly addresses your question.