cli, frontend: correctly check CoprDir before upload

We don't want to start uploading when the CoprDir format is invalid.

Follow-up-for: abb1bfe
Fixes: #2786

cli/copr_cli/main.py

@@ -327,10 +327,7 @@ def action_build(self, args):
         self.client.build_proxy.check_before_build(
             ownername=username,
             projectname=projectname,
-            # documentation says user can create directory with copr build, but
-            # /build/check-before-build endpoint checks for presence of this
-            # dirname even before creating it in this check.
-            project_dirname=None,
+            project_dirname=project_dirname,
             buildopts=buildopts,
         )
 

frontend/coprs_frontend/coprs/logic/coprs_logic.py

@@ -664,16 +664,10 @@ def _valid_custom_dir_suffix(copr, dirname):
         return all([c.isnumeric() for c in parts[2]])
 
     @classmethod
-    def get_or_create(cls, copr, dirname):
+    def validate(cls, copr, dirname):
         """
-        Create a CoprDir on-demand, e.g. before pull-request builds is
-        submitted.  We don't create the "main" CoprDirs here (those are created
-        when a new project is created.
+        Raise exception if dirname is invalid for copr.
         """
-        copr_dir = cls.get_by_copr_or_none(copr, dirname)
-        if copr_dir:
-            return copr_dir
-
         if not dirname.startswith(copr.name+':'):
             raise MalformedArgumentException(
                 "Copr dirname must start with '{}:' prefix".format(
@@ -691,6 +685,31 @@ def get_or_create(cls, copr, dirname):
                 f"Wrong directory '{dirname}' specified.  Directory name can "
                 "consist of alpha-numeric strings separated by colons.")
 
+    @classmethod
+    def get_or_validate(cls, copr, dirname):
+        """
+        Return the existing CoprDir object if it exists; otherwise, check
+        whether it can be created (has valid name) and return None.
+
+        Note that we first check if the directory exists, and then we perform
+        the name validation.  This is intentional for cases where the validation
+        rules may need to be changed in the future.  In such cases, we still
+        want to return existing directories that do not match the new rules.
+        """
+        if copr_dir := cls.get_by_copr_or_none(copr, dirname):
+            return copr_dir
+        cls.validate(copr, dirname)
+        return None
+
+    @classmethod
+    def get_or_create(cls, copr, dirname):
+        """
+        Create a CoprDir on-demand, e.g. before pull-request builds is
+        submitted.  We don't create the "main" CoprDirs here (those are created
+        when a new project is created.
+        """
+        if copr_dir := cls.get_or_validate(copr, dirname):
+            return copr_dir
         try:
             copr_dir = models.CoprDir(name=dirname, copr=copr, main=False)
             db.session.add(copr_dir)

frontend/coprs_frontend/coprs/views/apiv3_ns/apiv3_builds.py

@@ -229,7 +229,7 @@ def check_before_build():
 
     # Raises an exception if CoprDir doesn't exist
     if data.get("project_dirname"):
-        CoprDirsLogic.get_by_copr(copr, data["project_dirname"])
+        CoprDirsLogic.get_or_validate(copr, data["project_dirname"])
 
     # Permissions check
     if not flask.g.user.can_build_in(copr):