A new check f-string-without-interpolation was added

Close pylint-dev#3190

ChangeLog

@@ -18,6 +18,10 @@ Release date: TBA
 * ``inspect.getargvalues`` is no longer marked as deprecated.
 
 
+* A new check ``f-string-without-interpolation`` was added
+
+  Close #3190
+
 
 What's New in Pylint 2.4.3?
 ===========================

doc/whatsnew/2.5.rst

@@ -13,6 +13,12 @@ Summary -- Release highlights
 New checkers
 ============
 
+* A new check ``f-string-without-interpolation`` was added.
+
+  This check is emitted whenever **pylint** detects the use of an
+  f-string without having any interpolated values in it, which means
+  that the f-string can be a normal string.
+
 
 Other Changes
 =============
@@ -24,4 +30,3 @@ Other Changes
   A pyproject.toml file must prepend section names with ``tool.pylint.``,
   for example ``[tool.pylint.'MESSAGES CONTROL']``.
   These files can also be passed in on the command line.
-

pylint/checkers/strings.py

@@ -152,6 +152,12 @@
         "Used when we detect that a string formatting is "
         "repeating an argument instead of using named string arguments",
     ),
+    "W1309": (
+        "Using an f-string that does not have any interpolated variables",
+        "f-string-without-interpolation",
+        "Used when we detect an f-string that does not use any interpolation variables, "
+        "in which case it can be either a normal string or a bug in the code.",
+    ),
 }
 
 OTHER_NODES = (
@@ -333,6 +339,15 @@ def visit_binop(self, node):
                             args=(arg_type.pytype(), format_type),
                         )
 
+    @check_messages("f-string-without-interpolation")
+    def visit_joinedstr(self, node):
+        if isinstance(node.parent, astroid.FormattedValue):
+            return
+        for value in node.values:
+            if isinstance(value, astroid.FormattedValue):
+                return
+        self.add_message("f-string-without-interpolation", node=node)
+
     @check_messages(*MSGS)
     def visit_call(self, node):
         func = utils.safe_infer(node.func)

tests/functional/f/f_string_without_interpolation.py

@@ -0,0 +1,9 @@
+# pylint: disable=missing-module-docstring
+import math
+
+VALUE = 1
+
+print(f"some value {VALUE}")
+print(f'pi: {math.pi:.3f}')
+
+print(f"ERROR")  # [f-string-without-interpolation]

tests/functional/f/f_string_without_interpolation.rc

@@ -0,0 +1,2 @@
+[testoptions]
+min_pyver=3.6

tests/functional/f/f_string_without_interpolation.txt

@@ -0,0 +1 @@
+f-string-without-interpolation:9::Using an f-string that does not have any interpolated variables