Add tests for bogus combinators

See sass/sass#3340
See #1797

lib-js/spec-directory/virtual-directory.ts

@@ -72,7 +72,13 @@ export default class VirtualDirectory extends SpecDirectory {
     parentOpts?: SpecOptions
   ): Promise<VirtualDirectory> {
     const stream = fs.createReadStream(hrxPath, {encoding: 'utf-8'});
-    const archive = await archiveFromStream(stream);
+    let archive;
+    try {
+      archive = await archiveFromStream(stream);
+    } catch (error: unknown) {
+      throw new Error(`Error parsing ${hrxPath}: ${error}`);
+    }
+
     const {dir, name} = path.parse(hrxPath);
     return new VirtualDirectory(
       path.resolve(dir, name),

spec/core_functions/selector/append.hrx

@@ -119,6 +119,56 @@ a {
   structure: true;
 }
 
+<===>
+================================================================================
+<===> combinator/initial_leading/input.scss
+a {b: selector-append("> c", "d")}
+
+<===> combinator/initial_leading/output.css
+a {
+  b: > cd;
+}
+
+<===>
+================================================================================
+<===> combinator/final_trailing/input.scss
+a {b: selector-append("c", "d ~")}
+
+<===> combinator/final_trailing/output.css
+a {
+  b: cd ~;
+}
+
+<===>
+================================================================================
+<===> combinator/multiple/middle/input.scss
+a {b: selector-append("c > > d", "e")}
+
+<===> combinator/multiple/middle/output.css
+a {
+  b: c > > de;
+}
+
+<===>
+================================================================================
+<===> combinator/multiple/initial_leading/input.scss
+a {b: selector-append("~ ~ c", "d")}
+
+<===> combinator/multiple/initial_leading/output.css
+a {
+  b: ~ ~ cd;
+}
+
+<===>
+================================================================================
+<===> combinator/multiple/final_trailing/input.scss
+a {b: selector-append("c", "d + >")}
+
+<===> combinator/multiple/final_trailing/output.css
+a {
+  b: cd + >;
+}
+
 <===>
 ================================================================================
 <===> error/universal/options.yml
@@ -139,25 +189,51 @@ Error: Can't append * to .c.
 
 <===>
 ================================================================================
-<===> error/leading_combinator/input.scss
+<===> error/combinator/leading/input.scss
 a {b: selector-append(".c", "> .d")}
 
-<===> error/leading_combinator/error
+<===> error/combinator/leading/error
 Error: Can't append > .d to .c.
   ,
 1 | a {b: selector-append(".c", "> .d")}
   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   '
   input.scss 1:7  root stylesheet
 
-<===> error/leading_combinator/error-libsass
+<===> error/combinator/leading/error-libsass
 Error: Can't append "> .d" to ".c" for `selector-append'
         on line 1:7 of input.scss, in function `selector-append`
         from line 1:7 of input.scss
 >> a {b: selector-append(".c", "> .d")}
 
    ------^
 
+<===>
+================================================================================
+<===> error/combinator/trailing/input.scss
+a {b: selector-append(".c ~", ".d")}
+
+<===> error/combinator/trailing/error
+Error: Parent ".c ~" is incompatible with this selector.
+  ,
+1 | a {b: selector-append(".c ~", ".d")}
+  |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  '
+  input.scss 1:7  root stylesheet
+
+<===>
+================================================================================
+<===> error/combinator/only/input.scss
+a {b: selector-append(".c", ">", ".d")}
+
+<===> error/combinator/only/error
+Error: Can't append > to .c.
+  ,
+1 | a {b: selector-append(".c", ">", ".d")}
+  |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  '
+  input.scss 1:7  root stylesheet
+
 <===>
 ================================================================================
 <===> error/namespace/options.yml

spec/core_functions/selector/extend/complex/combinator_only.hrx

@@ -0,0 +1,41 @@
+<===> selector/input.scss
+a {b: selector-extend("+", ".c", ".d")}
+
+<===> selector/output.css
+a {
+  b: +;
+}
+
+<===> selector/warning
+DEPRECATION WARNING: $selector: + is not valid CSS.
+This will be an error in Dart Sass 2.0.0.
+
+More info: https://sass-lang.com/d/bogus-combinators
+
+  ,
+1 | a {b: selector-extend("+", ".c", ".d")}
+  |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  '
+    input.scss 1:7  root stylesheet
+
+<===>
+================================================================================
+<===> extender/input.scss
+a {b: selector-extend(".c", ".c", ">")}
+
+<===> extender/output.css
+a {
+  b: .c, >;
+}
+
+<===> extender/warning
+DEPRECATION WARNING: $extender: > is not valid CSS.
+This will be an error in Dart Sass 2.0.0.
+
+More info: https://sass-lang.com/d/bogus-combinators
+
+  ,
+1 | a {b: selector-extend(".c", ".c", ">")}
+  |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  '
+    input.scss 1:7  root stylesheet