Fix incorrect custom breakpoint indices when string group contains fa…

…ke f-strings (#2311) Fixes #2293
psf · Jun 7, 2021 · 99b68e5 · 99b68e5
1 parent 6380b9f
commit 99b68e5
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diff --git a/CHANGES.md b/CHANGES.md
@@ -9,6 +9,8 @@
 - Fixed option usage when using the `--code` flag (#2259)
 - Do not call `uvloop.install()` when _Black_ is used as a library (#2303)
 - 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)
 
 ## 21.5b2
 

diff --git a/src/black/trans.py b/src/black/trans.py
@@ -1151,21 +1151,32 @@ def more_splits_should_be_made() -> bool:
 
             # --- Construct `next_value`
             next_value = rest_value[:break_idx] + QUOTE
+
+            # HACK: The following 'if' statement is a hack to fix the custom
+            # breakpoint index in the case of either: (a) substrings that were
+            # f-strings but will have the 'f' prefix removed OR (b) substrings
+            # that were not f-strings but will now become f-strings because of
+            # redundant use of the 'f' prefix (i.e. none of the substrings
+            # contain f-expressions but one or more of them had the 'f' prefix
+            # anyway; in which case, we will prepend 'f' to _all_ substrings).
+            #
+            # There is probably a better way to accomplish what is being done
+            # here...
+            #
+            # If this substring is an f-string, we _could_ remove the 'f'
+            # prefix, and the current custom split did NOT originally use a
+            # prefix...
             if (
-                # Are we allowed to try to drop a pointless 'f' prefix?
-                drop_pointless_f_prefix
-                # If we are, will we be successful?
-                and next_value != self._normalize_f_string(next_value, prefix)
+                next_value != self._normalize_f_string(next_value, prefix)
+                and use_custom_breakpoints
+                and not csplit.has_prefix
             ):
-                # If the current custom split did NOT originally use a prefix,
-                # then `csplit.break_idx` will be off by one after removing
+                # Then `csplit.break_idx` will be off by one after removing
                 # the 'f' prefix.
-                break_idx = (
-                    break_idx + 1
-                    if use_custom_breakpoints and not csplit.has_prefix
-                    else break_idx
-                )
+                break_idx += 1
                 next_value = rest_value[:break_idx] + QUOTE
+
+            if drop_pointless_f_prefix:
                 next_value = self._normalize_f_string(next_value, prefix)
 
             # --- Construct `next_leaf`

diff --git a/tests/data/long_strings__regression.py b/tests/data/long_strings__regression.py
@@ -455,6 +455,45 @@ async def foo(self):
 )
 assert str(suffix_arr) in "['$', 'angaroo$', 'angrykangaroo$', 'aroo$', 'garoo$', 'grykangaroo$', 'kangaroo$', 'ngaroo$', 'ngrykangaroo$', 'o$', 'oo$', 'roo$', 'rykangaroo$', 'ykangaroo$']"
 assert str(suffix_arr) not in "['$', 'angaroo$', 'angrykangaroo$', 'aroo$', 'garoo$', 'grykangaroo$', 'kangaroo$', 'ngaroo$', 'ngrykangaroo$', 'o$', 'oo$', 'roo$', 'rykangaroo$', 'ykangaroo$']"
+message = (
+    f"1. Go to Google Developers Console and log in with your Google account."
+    "(https://console.developers.google.com/)"
+    "2. You should be prompted to create a new project (name does not matter)."
+    "3. Click on Enable APIs and Services at the top."
+    "4. In the list of APIs choose or search for YouTube Data API v3 and "
+    "click on it. Choose Enable."
+    "5. Click on Credentials on the left navigation bar."
+    "6. Click on Create Credential at the top."
+    '7. At the top click the link for "API key".'
+    "8. No application restrictions are needed. Click Create at the bottom."
+    "9. You now have a key to add to `{prefix}set api youtube api_key`"
+)
+message = (
+    f"1. Go to Google Developers Console and log in with your Google account."
+    "(https://console.developers.google.com/)"
+    "2. You should be prompted to create a new project (name does not matter)."
+    f"3. Click on Enable APIs and Services at the top."
+    "4. In the list of APIs choose or search for YouTube Data API v3 and "
+    "click on it. Choose Enable."
+    f"5. Click on Credentials on the left navigation bar."
+    "6. Click on Create Credential at the top."
+    '7. At the top click the link for "API key".'
+    "8. No application restrictions are needed. Click Create at the bottom."
+    "9. You now have a key to add to `{prefix}set api youtube api_key`"
+)
+message = (
+    f"1. Go to Google Developers Console and log in with your Google account."
+    "(https://console.developers.google.com/)"
+    "2. You should be prompted to create a new project (name does not matter)."
+    f"3. Click on Enable APIs and Services at the top."
+    "4. In the list of APIs choose or search for YouTube Data API v3 and "
+    "click on it. Choose Enable."
+    f"5. Click on Credentials on the left navigation bar."
+    "6. Click on Create Credential at the top."
+    '7. At the top click the link for "API key".'
+    "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`"
+)
 
 # output
 
@@ -1022,3 +1061,42 @@ async def foo(self):
     " 'kangaroo$', 'ngaroo$', 'ngrykangaroo$', 'o$', 'oo$', 'roo$',"
     " 'rykangaroo$', 'ykangaroo$']"
 )
+message = (
+    f"1. Go to Google Developers Console and log in with your Google account."
+    f"(https://console.developers.google.com/)"
+    f"2. You should be prompted to create a new project (name does not matter)."
+    f"3. Click on Enable APIs and Services at the top."
+    f"4. In the list of APIs choose or search for YouTube Data API v3 and "
+    f"click on it. Choose Enable."
+    f"5. Click on Credentials on the left navigation bar."
+    f"6. Click on Create Credential at the top."
+    f'7. At the top click the link for "API key".'
+    f"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`"
+)
+message = (
+    f"1. Go to Google Developers Console and log in with your Google account."
+    f"(https://console.developers.google.com/)"
+    f"2. You should be prompted to create a new project (name does not matter)."
+    f"3. Click on Enable APIs and Services at the top."
+    f"4. In the list of APIs choose or search for YouTube Data API v3 and "
+    f"click on it. Choose Enable."
+    f"5. Click on Credentials on the left navigation bar."
+    f"6. Click on Create Credential at the top."
+    f'7. At the top click the link for "API key".'
+    f"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`"
+)
+message = (
+    "1. Go to Google Developers Console and log in with your Google account."
+    "(https://console.developers.google.com/)"
+    "2. You should be prompted to create a new project (name does not matter)."
+    "3. Click on Enable APIs and Services at the top."
+    "4. In the list of APIs choose or search for YouTube Data API v3 and "
+    "click on it. Choose Enable."
+    "5. Click on Credentials on the left navigation bar."
+    "6. Click on Create Credential at the top."
+    '7. At the top click the link for "API key".'
+    "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`"
+)