Build details page: normalize/trim command paths (second attempt)

Continuation of the work done in
#9815 that didn't work as we
expected.

We weren't saving the commands properly when hitting the API since
`serializers.SerializerMethodField` is a read-only field. This commit fixes this
problem by using a different Serializer depending if it's a GET request or not,
and if it's made by an Admin or not.

It overrides the method `BuildViewSet.get_serializer_class` to manage these
different cases and return the proper serializer.

Done on top of #9815 to be sure the
tests for saving commands are passing.

readthedocs/api/v2/serializers.py

@@ -1,6 +1,9 @@
 """Defines serializers for each of our models."""
 
+import re
+
 from allauth.socialaccount.models import SocialAccount
+from django.conf import settings
 from rest_framework import serializers
 
 from readthedocs.builds.models import Build, BuildCommandResult, Version
@@ -133,11 +136,49 @@ class Meta:
         exclude = []
 
 
+class BuildCommandUISerializer(BuildCommandSerializer):
+    """
+    Serializer used on GETs to trimm the commands' path.
+
+    Remove unreadable paths from the command outputs when returning it from the API.
+    We could make this change at build level, but we want to avoid undoable issues from now
+    and hack a small solution to fix the immediate problem.
+
+    This converts:
+        $ /usr/src/app/checkouts/readthedocs.org/user_builds/
+            <container_hash>/<project_slug>/envs/<version_slug>/bin/python
+        $ /home/docs/checkouts/readthedocs.org/user_builds/
+            <project_slug>/envs/<version_slug>/bin/python
+    into
+        $ python
+    """
+
+    command = serializers.SerializerMethodField()
+
+    def get_command(self, obj):
+        project_slug = obj.build.version.project.slug
+        version_slug = obj.build.version.slug
+        docroot = settings.DOCROOT.rstrip("/")  # remove trailing '/'
+
+        # Remove Docker hash from DOCROOT when running it locally
+        # DOCROOT contains the Docker container hash (e.g. b7703d1b5854).
+        # We have to remove it from the DOCROOT it self since it changes each time
+        # we spin up a new Docker instance locally.
+        container_hash = "/"
+        if settings.RTD_DOCKER_COMPOSE:
+            docroot = re.sub("/[0-9a-z]+/?$", "", settings.DOCROOT, count=1)
+            container_hash = "/[0-9a-z]+/"
+
+        regex = f"{docroot}{container_hash}{project_slug}/envs/{version_slug}(/bin/)?"
+        command = re.sub(regex, "", obj.command, count=1)
+        return command
+
+
 class BuildSerializer(serializers.ModelSerializer):
 
     """Build serializer for user display, doesn't display internal fields."""
 
-    commands = BuildCommandSerializer(many=True, read_only=True)
+    commands = BuildCommandUISerializer(many=True, read_only=True)
     project_slug = serializers.ReadOnlyField(source='project.slug')
     version_slug = serializers.ReadOnlyField(source='get_version_slug')
     docs_url = serializers.SerializerMethodField()
@@ -162,11 +203,17 @@ class BuildAdminSerializer(BuildSerializer):
 
     """Build serializer for display to admin users and build instances."""
 
+    commands = BuildCommandSerializer(many=True, read_only=True)
+
     class Meta(BuildSerializer.Meta):
         # `_config` should be excluded to avoid conflicts with `config`
         exclude = ('_config',)
 
 
+class BuildAdminUISerializer(BuildAdminSerializer):
+    commands = BuildCommandUISerializer(many=True, read_only=True)
+
+
 class SearchIndexSerializer(serializers.Serializer):
     q = serializers.CharField(max_length=500)
     project = serializers.CharField(max_length=500, required=False)

readthedocs/api/v2/views/model_views.py

@@ -23,6 +23,7 @@
 from ..permissions import APIPermission, APIRestrictedPermission, IsOwner
 from ..serializers import (
     BuildAdminSerializer,
+    BuildAdminUISerializer,
     BuildCommandSerializer,
     BuildSerializer,
     DomainSerializer,
@@ -224,11 +225,25 @@ class VersionViewSet(DisableListEndpoint, UserSelectViewSet):
 class BuildViewSet(DisableListEndpoint, UserSelectViewSet):
     permission_classes = [APIRestrictedPermission]
     renderer_classes = (JSONRenderer, PlainTextBuildRenderer)
-    serializer_class = BuildSerializer
-    admin_serializer_class = BuildAdminSerializer
     model = Build
     filterset_fields = ('project__slug', 'commit')
 
+    def get_serializer_class(self):
+        """
+        Return the proper serializer for UI and Admin.
+
+        This ViewSet has a sligtly different pattern since we want to
+        pre-process the `command` field before returning it to the user, and we
+        also want to have a specific serializer for admins.
+        """
+        if self.request.user.is_staff:
+            # Logic copied from `UserSelectViewSet.get_serializer_class`
+            # and extended to check for GET method
+            if self.request.method == "GET":
+                return BuildAdminUISerializer
+            return BuildAdminSerializer
+        return BuildSerializer
+
     @decorators.action(
         detail=False,
         permission_classes=[permissions.IsAdminUser],