Merge pull request #1320 from ISISScientificComputing/allow_null_variable_value

Author: Dimitar Tasev

WebApp/autoreduce_webapp/autoreduce_webapp/fixtures/run_with_multiple_variables.json

@@ -119,7 +119,7 @@
         "pk": 6,
         "fields": {
             "name": "variable_none",
-            "value": "None",
+            "value": null,
             "type": "text",
             "is_advanced": false,
             "help_text": ""

WebApp/autoreduce_webapp/instrument/migrations/0002_auto_20210426_1519.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.1.2 on 2021-04-26 14:19
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('instrument', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='variable',
+            name='value',
+            field=models.CharField(blank=True, max_length=300, null=True),
+        ),
+    ]

WebApp/autoreduce_webapp/instrument/migrations/0003_merge_20210426_1528.py

@@ -0,0 +1,14 @@
+# Generated by Django 3.1.2 on 2021-04-26 14:28
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('instrument', '0002_auto_20210426_1519'),
+        ('instrument', '0002_alter_variable_value'),
+    ]
+
+    operations = [
+    ]

WebApp/autoreduce_webapp/instrument/models.py

@@ -16,15 +16,11 @@ class Variable(models.Model):
     Generic model class that should be treated as abstract
     """
     name = models.CharField(max_length=50, blank=False)
-    value = models.CharField(max_length=300, blank=True)
+    value = models.CharField(max_length=300, blank=True, null=True)
     type = models.CharField(max_length=50, blank=False)
     is_advanced = models.BooleanField(default=False)
     help_text = models.TextField(blank=True, null=True, default='')
 
-    # pylint:disable=no-member
-    def __str__(self):
-        return f"{self.instrument.name} - {self.name}=self.value"
-
     def sanitized_name(self):
         """
         Returns a HTMl-friendly name that can be used as element IDs or form input names
@@ -48,6 +44,10 @@ class InstrumentVariable(Variable):
     start_run = models.IntegerField(blank=True, null=True)
     tracks_script = models.BooleanField(default=False)
 
+    # pylint:disable=no-member
+    def __str__(self):
+        return f"{self.instrument.name} - {self.name}=self.value"
+
 
 class RunVariable(models.Model):
     """