From 36e7dfaa0ecd2b2d4b332aa0dc5c2855ba8aa946 Mon Sep 17 00:00:00 2001
From: David-Wobrock <david.wobrock@gmail.com>
Date: Sun, 24 Feb 2019 18:18:45 +0100
Subject: [PATCH] Do not create cache folder if no-cache option

---
 django_migration_linter/cache.py            |  9 ----
 django_migration_linter/migration.py        | 33 ++++++++------
 django_migration_linter/migration_linter.py | 48 ++++++++++++---------
 3 files changed, 48 insertions(+), 42 deletions(-)

diff --git a/django_migration_linter/cache.py b/django_migration_linter/cache.py
index aa28578..d64ef3e 100644
--- a/django_migration_linter/cache.py
+++ b/django_migration_linter/cache.py
@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import hashlib
 import os
 import pickle
 
@@ -41,11 +40,3 @@ class Cache(dict):
     def save(self):
         with open(self.filename, "wb") as f:
             pickle.dump(self, f, protocol=2)
-
-    @staticmethod
-    def md5(path):
-        hash_md5 = hashlib.md5()
-        with open(path, "rb") as f:
-            for chunk in iter(lambda: f.read(4096), b""):
-                hash_md5.update(chunk)
-        return hash_md5.hexdigest()
diff --git a/django_migration_linter/migration.py b/django_migration_linter/migration.py
index 004f64c..c24a2ae 100644
--- a/django_migration_linter/migration.py
+++ b/django_migration_linter/migration.py
@@ -1,12 +1,21 @@
-from django_migration_linter.utils import split_migration_path
-
-
-class Migration(object):
-    def __init__(self, abs_path):
-        self.abs_path = abs_path
-        self.app_name, self.name = split_migration_path(self.abs_path)
-
-    def __lt__(self, other):
-        if not isinstance(other, Migration):
-            return NotImplemented
-        return self.abs_path < other.abs_path
+import hashlib
+
+from django_migration_linter.utils import split_migration_path
+
+
+class Migration(object):
+    def __init__(self, abs_path):
+        self.abs_path = abs_path
+        self.app_name, self.name = split_migration_path(self.abs_path)
+
+    def __lt__(self, other):
+        if not isinstance(other, Migration):
+            return NotImplemented
+        return self.abs_path < other.abs_path
+
+    def get_md5hash(self):
+        hash_md5 = hashlib.md5()
+        with open(self.abs_path, "rb") as f:
+            for chunk in iter(lambda: f.read(4096), b""):
+                hash_md5.update(chunk)
+        return hash_md5.hexdigest()
diff --git a/django_migration_linter/migration_linter.py b/django_migration_linter/migration_linter.py
index 2b557ca..ee6651c 100644
--- a/django_migration_linter/migration_linter.py
+++ b/django_migration_linter/migration_linter.py
@@ -61,9 +61,9 @@ class MigrationLinter(object):
         self.nb_total = 0
 
         # Initialise cache. Read from old, write to new to prune old entries.
-        self.old_cache = Cache(self.django_path, self.cache_path)
-        self.new_cache = Cache(self.django_path, self.cache_path)
         if not self.no_cache:
+            self.old_cache = Cache(self.django_path, self.cache_path)
+            self.new_cache = Cache(self.django_path, self.cache_path)
             self.old_cache.load()
 
     def lint_migration(self, migration):
@@ -72,22 +72,9 @@ class MigrationLinter(object):
         print("({0}, {1})... ".format(app_name, migration_name), end="")
         self.nb_total += 1
 
-        md5hash = self.old_cache.md5(migration.abs_path)
-        if md5hash in self.old_cache:
-            if self.old_cache[md5hash]["result"] == "IGNORE":
-                print("IGNORE (cached)")
-                self.nb_ignored += 1
-            elif self.old_cache[md5hash]["result"] == "OK":
-                print("OK (cached)")
-                self.nb_valid += 1
-            else:
-                print("ERR (cached)")
-                self.nb_erroneous += 1
-
-            if "errors" in self.old_cache[md5hash]:
-                self.print_errors(self.old_cache[md5hash]["errors"])
-
-            self.new_cache[md5hash] = self.old_cache[md5hash]
+        md5hash = migration.get_md5hash()
+        if not self.no_cache and md5hash in self.old_cache:
+            self.lint_cached_migration(md5hash)
             return
 
         if self.should_ignore_migration(app_name, migration_name):
@@ -101,20 +88,39 @@ class MigrationLinter(object):
 
         if analysis_result["ignored"]:
             print("IGNORE")
-            self.new_cache[md5hash] = {"result": "IGNORE"}
             self.nb_ignored += 1
+            if not self.no_cache:
+                self.new_cache[md5hash] = {"result": "IGNORE"}
             return
 
         if not errors:
             print("OK")
-            self.new_cache[md5hash] = {"result": "OK"}
             self.nb_valid += 1
+            if not self.no_cache:
+                self.new_cache[md5hash] = {"result": "OK"}
             return
 
         print("ERR")
-        self.new_cache[md5hash] = {"result": "ERR", "errors": errors}
         self.nb_erroneous += 1
         self.print_errors(errors)
+        if not self.no_cache:
+            self.new_cache[md5hash] = {"result": "ERR", "errors": errors}
+
+    def lint_cached_migration(self, md5hash):
+        cached_value = self.old_cache[md5hash]
+        if cached_value["result"] == "IGNORE":
+            print("IGNORE (cached)")
+            self.nb_ignored += 1
+        elif cached_value["result"] == "OK":
+            print("OK (cached)")
+            self.nb_valid += 1
+        else:
+            print("ERR (cached)")
+            self.nb_erroneous += 1
+            if "errors" in cached_value:
+                self.print_errors(cached_value["errors"])
+
+        self.new_cache[md5hash] = cached_value
 
     @staticmethod
     def print_errors(errors):