mangle: add the blank line after the EAPI assignment

Resolves: #127
Signed-off-by: Arthur Zamarin <arthurzam@gentoo.org>

Author: arthurzam

NEWS.rst

@@ -30,6 +30,9 @@ pkgdev 0.2.18 (unreleased)
   and having its caches invalidated through a pkgcore internal meant for
   mutable repositories (Arthur Zamarin, #172)
 
+- commit: the mangler now adds the blank line after the ``EAPI=`` assignment
+  (Arthur Zamarin, #127)
+
 **pkgdev showkw:**
 
 - showkw: drop the vendored copy of tabulate in favor of a dependency on

src/pkgdev/mangle.py

@@ -31,9 +31,9 @@ class decorator:
         def __init__(self, func):
             self.func = func
 
-        def __set_name__(self, owner, name):
+        def __set_name__(self, owner, attr):
             owner._mangle_funcs[name] = self.func
-            setattr(owner, name, self.func)
+            setattr(owner, attr, self.func)
 
     return decorator
 
@@ -70,6 +70,17 @@ def _eof(self, change):
         """Drop EOF whitespace and forcibly add EOF newline."""
         return change.update(change.data.rstrip() + "\n")
 
+    @mangle("eapi-blank-line")
+    def _eapi_blank_line(self, change):
+        """Add the blank line after the EAPI assignment."""
+        lines = change.data.splitlines()
+        for i, line in enumerate(lines):
+            if line.startswith("EAPI="):
+                if i + 1 < len(lines) and lines[i + 1] != "":
+                    lines.insert(i + 1, "")
+                break
+        return change.update("\n".join(lines) + "\n")
+
     @mangle("keywords")
     def _keywords(self, change):
         """Fix keywords order."""

tests/scripts/test_pkgdev_commit.py

@@ -1046,6 +1046,27 @@ def commit(args):
                 assert mo.group("begin") == years[:4] + "-"
                 assert mo.group("holder") == "Gentoo Authors"
 
+        # keep the rest of the ebuild, only the spacing after EAPI= varies
+        with open(ebuild_path) as f:
+            lines = f.read().splitlines()
+        eapi_lineno = next(i for i, line in enumerate(lines) if line.startswith("EAPI="))
+        head, rest = lines[: eapi_lineno + 1], [x for x in lines[eapi_lineno + 1 :] if x]
+
+        for original, expected in (
+            (["# comment"], ["", "# comment"]),
+            (["", "# comment"], ["", "# comment"]),
+            # a line which merely looks empty isn't one
+            ([" ", "# comment"], ["", " ", "# comment"]),
+        ):
+            # munge the lines after the EAPI assignment
+            with open(ebuild_path, "w") as f:
+                f.write("\n".join(head + original + rest) + "\n")
+            commit(["-n", "-u", "-m", "mangling"])
+            # verify the blank line after EAPI= is there
+            with open(ebuild_path) as f:
+                mangled = f.read().splitlines()
+                assert mangled[eapi_lineno + 1 : eapi_lineno + 1 + len(expected)] == expected
+
         for original, expected in (
             ('"arm64 amd64 x86"', "amd64 arm64 x86"),
             ('"arm64 amd64 ~x86"', "amd64 arm64 ~x86"),