feat: Support nested declarations in fuzzy attributes

Recursive resolution of declarations in BaseFuzzyAttribute.
Fixes #1050

- BaseFuzzyAttribute now resolves nested declarations (e.g. LazyAttribute)
- Updated FuzzyChoice, FuzzyInteger, FuzzyFloat, FuzzyDate, FuzzyDateTime
- Added tests for nested declarations in all fuzzy types
- Updated documentation

Author: rodrigo.nogueira

docs/ideas.rst

@@ -6,4 +6,4 @@ This is a list of future features that may be incorporated into factory_boy:
 
 * When a :class:`~factory.Factory` is built or created, pass the calling context throughout the calling chain instead of custom solutions everywhere
 * Define a proper set of rules for the support of third-party ORMs
-* Properly evaluate nested declarations (e.g ``factory.fuzzy.FuzzyDate(start_date=factory.SelfAttribute('since'))``)
+* Properly evaluate nested declarations (e.g ``factory.fuzzy.FuzzyDate(start_date=factory.SelfAttribute('since'))``) (Accomplished)

factory/fuzzy.py

@@ -24,11 +24,16 @@ class BaseFuzzyAttribute(declarations.BaseDeclaration):
     Custom fuzzers should override the `fuzz()` method.
     """
 
-    def fuzz(self):  # pragma: no cover
+    def _resolve(self, value, instance, step):
+        if isinstance(value, declarations.BaseDeclaration):
+            return value.evaluate_pre(instance=instance, step=step, overrides={})
+        return value
+
+    def fuzz(self, instance, step):
         raise NotImplementedError()
 
     def evaluate(self, instance, step, extra):
-        return self.fuzz()
+        return self.fuzz(instance, step)
 
 
 class FuzzyAttribute(BaseFuzzyAttribute):
@@ -43,7 +48,7 @@ def __init__(self, fuzzer):
         super().__init__()
         self.fuzzer = fuzzer
 
-    def fuzz(self):
+    def fuzz(self, instance, step):
         return self.fuzzer()
 
 
@@ -71,7 +76,7 @@ def __init__(self, prefix='', length=12, suffix='', chars=string.ascii_letters):
         self.length = length
         self.chars = tuple(chars)  # Unroll iterators
 
-    def fuzz(self):
+    def fuzz(self, instance, step):
         chars = [random.randgen.choice(self.chars) for _i in range(self.length)]
         return self.prefix + ''.join(chars) + self.suffix
 
@@ -91,9 +96,10 @@ def __init__(self, choices, getter=None):
         self.getter = getter
         super().__init__()
 
-    def fuzz(self):
+    def fuzz(self, instance, step):
         if self.choices is None:
-            self.choices = list(self.choices_generator)
+            resolved = self._resolve(self.choices_generator, instance, step)
+            self.choices = list(resolved)
         value = random.randgen.choice(self.choices)
         if self.getter is None:
             return value
@@ -104,55 +110,55 @@ class FuzzyInteger(BaseFuzzyAttribute):
     """Random integer within a given range."""
 
     def __init__(self, low, high=None, step=1):
-        if high is None:
-            high = low
-            low = 0
-
         self.low = low
         self.high = high
         self.step = step
-
         super().__init__()
 
-    def fuzz(self):
-        return random.randgen.randrange(self.low, self.high + 1, self.step)
+    def fuzz(self, instance, step):
+        low = self._resolve(self.low, instance, step)
+        high = self._resolve(self.high, instance, step)
+        if high is None:
+            high = low
+            low = 0
+        return random.randgen.randrange(low, high + 1, self.step)
 
 
 class FuzzyDecimal(BaseFuzzyAttribute):
     """Random decimal within a given range."""
 
     def __init__(self, low, high=None, precision=2):
-        if high is None:
-            high = low
-            low = 0.0
-
         self.low = low
         self.high = high
         self.precision = precision
-
         super().__init__()
 
-    def fuzz(self):
-        base = decimal.Decimal(str(random.randgen.uniform(self.low, self.high)))
+    def fuzz(self, instance, step):
+        low = self._resolve(self.low, instance, step)
+        high = self._resolve(self.high, instance, step)
+        if high is None:
+            high = low
+            low = 0.0
+        base = decimal.Decimal(str(random.randgen.uniform(low, high)))
         return base.quantize(decimal.Decimal(10) ** -self.precision)
 
 
 class FuzzyFloat(BaseFuzzyAttribute):
     """Random float within a given range."""
 
     def __init__(self, low, high=None, precision=15):
-        if high is None:
-            high = low
-            low = 0
-
         self.low = low
         self.high = high
         self.precision = precision
-
         super().__init__()
 
-    def fuzz(self):
-        base = random.randgen.uniform(self.low, self.high)
+    def fuzz(self, instance, step):
+        low = self._resolve(self.low, instance, step)
+        high = self._resolve(self.high, instance, step)
+        if high is None:
+            high = low
+            low = 0
+        base = random.randgen.uniform(low, high)
         return float(format(base, '.%dg' % self.precision))
 
 
@@ -161,22 +167,40 @@ class FuzzyDate(BaseFuzzyAttribute):
 
     def __init__(self, start_date, end_date=None):
         super().__init__()
-        if end_date is None:
-            if random.randgen.state_set:
-                cls_name = self.__class__.__name__
-                warnings.warn(random_seed_warning.format(cls_name), stacklevel=2)
-            end_date = datetime.date.today()
-
-        if start_date > end_date:
-            raise ValueError(
-                "FuzzyDate boundaries should have start <= end; got %r > %r."
-                % (start_date, end_date))
-
-        self.start_date = start_date.toordinal()
-        self.end_date = end_date.toordinal()
-
-    def fuzz(self):
-        return datetime.date.fromordinal(random.randgen.randint(self.start_date, self.end_date))
+        self._start_is_decl = isinstance(start_date, declarations.BaseDeclaration)
+        self._end_is_decl = isinstance(end_date, declarations.BaseDeclaration)
+        self.start_date = start_date
+        self.end_date = end_date
+        if not self._start_is_decl and not self._end_is_decl:
+            if end_date is None:
+                if random.randgen.state_set:
+                    cls_name = self.__class__.__name__
+                    warnings.warn(random_seed_warning.format(cls_name), stacklevel=2)
+                end_date = datetime.date.today()
+                self.end_date = end_date
+            if start_date > end_date:
+                raise ValueError(
+                    "FuzzyDate boundaries should have start <= end; got %r > %r."
+                    % (start_date, end_date))
+            self._start_ord = start_date.toordinal()
+            self._end_ord = end_date.toordinal()
+
+    def fuzz(self, instance, step):
+        if self._start_is_decl or self._end_is_decl:
+            start_date = self._resolve(self.start_date, instance, step)
+            end_date = self._resolve(self.end_date, instance, step)
+            if end_date is None:
+                end_date = datetime.date.today()
+            if start_date > end_date:
+                raise ValueError(
+                    "FuzzyDate boundaries should have start <= end; got %r > %r."
+                    % (start_date, end_date))
+            start_ord = start_date.toordinal()
+            end_ord = end_date.toordinal()
+        else:
+            start_ord = self._start_ord
+            end_ord = self._end_ord
+        return datetime.date.fromordinal(random.randgen.randint(start_ord, end_ord))
 
 
 class BaseFuzzyDateTime(BaseFuzzyAttribute):
@@ -199,15 +223,8 @@ def __init__(self, start_dt, end_dt=None,
                  force_hour=None, force_minute=None, force_second=None,
                  force_microsecond=None):
         super().__init__()
-
-        if end_dt is None:
-            if random.randgen.state_set:
-                cls_name = self.__class__.__name__
-                warnings.warn(random_seed_warning.format(cls_name), stacklevel=2)
-            end_dt = self._now()
-
-        self._check_bounds(start_dt, end_dt)
-
+        self._start_is_decl = isinstance(start_dt, declarations.BaseDeclaration)
+        self._end_is_decl = isinstance(end_dt, declarations.BaseDeclaration)
         self.start_dt = start_dt
         self.end_dt = end_dt
         self.force_year = force_year
@@ -217,13 +234,31 @@ def __init__(self, start_dt, end_dt=None,
         self.force_minute = force_minute
         self.force_second = force_second
         self.force_microsecond = force_microsecond
-
-    def fuzz(self):
-        delta = self.end_dt - self.start_dt
+        if not self._start_is_decl and not self._end_is_decl:
+            if end_dt is None:
+                if random.randgen.state_set:
+                    cls_name = self.__class__.__name__
+                    warnings.warn(random_seed_warning.format(cls_name), stacklevel=2)
+                end_dt = self._now()
+                self.end_dt = end_dt
+            self._check_bounds(start_dt, end_dt)
+
+    def fuzz(self, instance, step):
+        if self._start_is_decl or self._end_is_decl:
+            start_dt = self._resolve(self.start_dt, instance, step)
+            end_dt = self._resolve(self.end_dt, instance, step)
+            if end_dt is None:
+                end_dt = self._now()
+            self._check_bounds(start_dt, end_dt)
+        else:
+            start_dt = self.start_dt
+            end_dt = self.end_dt
+
+        delta = end_dt - start_dt
         microseconds = delta.microseconds + 1000000 * (delta.seconds + (delta.days * 86400))
 
         offset = random.randgen.randint(0, microseconds)
-        result = self.start_dt + datetime.timedelta(microseconds=offset)
+        result = start_dt + datetime.timedelta(microseconds=offset)
 
         if self.force_year is not None:
             result = result.replace(year=self.force_year)