Regression fix: leave R prefixes capitalization alone (#2285)

`black.strings.get_string_prefix` used to lowercase the extracted
prefix before returning it. This is wrong because 1) it ignores the
fact we should leave R prefixes alone because of MagicPython, and 2)
there is dedicated prefix casing handling code that fixes issue 1.
`.lower` is too naive.

This was originally fixed in 20.8b0, but was reintroduced since 21.4b0.

I also added proper prefix normalization for docstrings by using the
`black.strings.normalize_string_prefix` helper.

Some more test strings were added to make sure strings with capitalized
prefixes aren't treated differently (actually happened with my original
patch, Jelle had to point it out to me).

diff --git a/CHANGES.md b/CHANGES.md
index 2d2b3b4cf49303d1c33cf1f8e09b35525327034f..9c2939e1b1bd6e3aaa5edbaa86726aa44a71c605 100644 (file)
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -12,6 +12,7 @@
 - Added `--required-version` option to require a specific version to be running (#2300)
 - Fix incorrect custom breakpoint indices when string group contains fake f-strings
   (#2311)
+- Fix regression where `R` prefixes would be lowercased for docstrings (#2285)
 
 ## 21.5b2
 

diff --git a/src/black/linegen.py b/src/black/linegen.py
index 7949654b40e5a4dee405c1182816a5f4363f0f87..3b811f02b7c6383c8aecc1904dee8c1480121a0f 100644 (file)
--- a/src/black/linegen.py
+++ b/src/black/linegen.py
@@ -226,8 +226,9 @@ class LineGenerator(Visitor[Line]):
         if is_docstring(leaf) and "\\\n" not in leaf.value:
             # We're ignoring docstrings with backslash newline escapes because changing
             # indentation of those changes the AST representation of the code.
-            prefix = get_string_prefix(leaf.value)
-            docstring = leaf.value[len(prefix) :]  # Remove the prefix
+            docstring = normalize_string_prefix(leaf.value, self.remove_u_prefix)
+            prefix = get_string_prefix(docstring)
+            docstring = docstring[len(prefix) :]  # Remove the prefix
             quote_char = docstring[0]
             # A natural way to remove the outer quotes is to do:
             #   docstring = docstring.strip(quote_char)

diff --git a/src/black/strings.py b/src/black/strings.py
index 5b443ddebc9e7e662b469b2c2717052ff2dcbf99..80f588f5119c4432c4a43ce8414b014893b4be2b 100644 (file)
--- a/src/black/strings.py
+++ b/src/black/strings.py
@@ -87,7 +87,7 @@ def get_string_prefix(string: str) -> str:
     prefix = ""
     prefix_idx = 0
     while string[prefix_idx] in STRING_PREFIX_CHARS:
-        prefix += string[prefix_idx].lower()
+        prefix += string[prefix_idx]
         prefix_idx += 1
 
     return prefix

diff --git a/src/black/trans.py b/src/black/trans.py
index 4fb2c4d01440b89ef9c6408d3c94cc9e4745f018..ca620f6b2a5dd4236d5cc45e380e03604380b8e1 100644 (file)
--- a/src/black/trans.py
+++ b/src/black/trans.py
@@ -411,7 +411,7 @@ class StringMerger(CustomSplitMapMixin, StringTransformer):
             and is_valid_index(next_str_idx)
             and LL[next_str_idx].type == token.STRING
         ):
-            prefix = get_string_prefix(LL[next_str_idx].value)
+            prefix = get_string_prefix(LL[next_str_idx].value).lower()
             next_str_idx += 1
 
         # The next loop merges the string group. The final string will be
@@ -431,7 +431,7 @@ class StringMerger(CustomSplitMapMixin, StringTransformer):
             num_of_strings += 1
 
             SS = LL[next_str_idx].value
-            next_prefix = get_string_prefix(SS)
+            next_prefix = get_string_prefix(SS).lower()
 
             # If this is an f-string group but this substring is not prefixed
             # with 'f'...
@@ -541,7 +541,7 @@ class StringMerger(CustomSplitMapMixin, StringTransformer):
                 return TErr("StringMerger does NOT merge multiline strings.")
 
             num_of_strings += 1
-            prefix = get_string_prefix(leaf.value)
+            prefix = get_string_prefix(leaf.value).lower()
             if "r" in prefix:
                 return TErr("StringMerger does NOT merge raw strings.")
 
@@ -1036,7 +1036,7 @@ class StringSplitter(CustomSplitMapMixin, BaseStringSplitter):
         is_valid_index = is_valid_index_factory(LL)
         insert_str_child = insert_str_child_factory(LL[string_idx])
 
-        prefix = get_string_prefix(LL[string_idx].value)
+        prefix = get_string_prefix(LL[string_idx].value).lower()
 
         # We MAY choose to drop the 'f' prefix from substrings that don't
         # contain any f-expressions, but ONLY if the original f-string
@@ -1290,7 +1290,7 @@ class StringSplitter(CustomSplitMapMixin, BaseStringSplitter):
 
             yield from _fexpr_slices
 
-        is_fstring = "f" in get_string_prefix(string)
+        is_fstring = "f" in get_string_prefix(string).lower()
 
         def breaks_fstring_expression(i: Index) -> bool:
             """

diff --git a/tests/data/long_strings__regression.py b/tests/data/long_strings__regression.py
index 83cae614e69c7198db3700bfeffab21abb230c96..e4234b2f97c160d98e11e8e2127d94c37d9e2d75 100644 (file)
--- a/tests/data/long_strings__regression.py
+++ b/tests/data/long_strings__regression.py
@@ -495,6 +495,26 @@ message = (
     f"9. You now have a key to add to `{prefix}set api youtube api_key`"
 )
 
+# It shouldn't matter if the string prefixes are capitalized.
+temp_msg = (
+    F"{F'{humanize_number(pos)}.': <{pound_len+2}} "
+    F"{balance: <{bal_len + 5}} "
+    F"<<{author.display_name}>>\n"
+)
+
+fstring = (
+    F"We have to remember to escape {braces}."
+    " Like {these}."
+    F" But not {this}."
+)
+
+welcome_to_programming = R"hello," R" world!"
+
+fstring = F"f-strings definitely make things more {difficult} than they need to be for {{black}}. But boy they sure are handy. The problem is that some lines will need to have the 'f' whereas others do not. This {line}, for example, needs one."
+
+x = F"This is a long string which contains an f-expr that should not split {{{[i for i in range(5)]}}}."
+
+
 # output
 
 
@@ -1100,3 +1120,25 @@ message = (
     "8. No application restrictions are needed. Click Create at the bottom."
     f"9. You now have a key to add to `{prefix}set api youtube api_key`"
 )
+
+# It shouldn't matter if the string prefixes are capitalized.
+temp_msg = (
+    f"{F'{humanize_number(pos)}.': <{pound_len+2}} "
+    f"{balance: <{bal_len + 5}} "
+    f"<<{author.display_name}>>\n"
+)
+
+fstring = f"We have to remember to escape {braces}. Like {{these}}. But not {this}."
+
+welcome_to_programming = R"hello," R" world!"
+
+fstring = (
+    f"f-strings definitely make things more {difficult} than they need to be for"
+    " {black}. But boy they sure are handy. The problem is that some lines will need"
+    f" to have the 'f' whereas others do not. This {line}, for example, needs one."
+)
+
+x = (
+    "This is a long string which contains an f-expr that should not split"
+    f" {{{[i for i in range(5)]}}}."
+)

diff --git a/tests/data/string_prefixes.py b/tests/data/string_prefixes.py
index 0ca3686a2b6c0fee3004c0e78c066b24b1b0c5a1..9ddc2b540fcefe3c729e198cdc9e6ba5da5f4861 100644 (file)
--- a/tests/data/string_prefixes.py
+++ b/tests/data/string_prefixes.py
@@ -6,6 +6,17 @@ B"hello"
 r"hello"
 fR"hello"
 
+
+def docstring_singleline():
+    R"""2020 was one hell of a year. The good news is that we were able to"""
+
+
+def docstring_multiline():
+    R"""
+    clear out all of the issues opened in that time :p
+    """
+
+
 # output
 
 
@@ -16,3 +27,13 @@ f"hello {name}"
 b"hello"
 r"hello"
 fR"hello"
+
+
+def docstring_singleline():
+    R"""2020 was one hell of a year. The good news is that we were able to"""
+
+
+def docstring_multiline():
+    R"""
+    clear out all of the issues opened in that time :p
+    """