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Improve warnings about unnecessary subshells (fixes #2169)

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Vidar Holen 2021-08-30 10:56:55 -07:00
parent 10817533d6
commit f5fd9c2fed
1 changed files with 29 additions and 5 deletions
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34
src/ShellCheck/Analytics.hs
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@ -3742,21 +3742,27 @@ checkForLoopGlobVariables _ t =
suggest t = info (getId t) 2231 suggest t = info (getId t) 2231
"Quote expansions in this for loop glob to prevent wordsplitting, e.g. \"$dir\"/*.txt ." "Quote expansions in this for loop glob to prevent wordsplitting, e.g. \"$dir\"/*.txt ."
prop_checkSubshelledTests1 = verify checkSubshelledTests "a && ( [ b ] || ! [ c ] )" prop_checkSubshelledTests1 = verify checkSubshelledTests "a && ( [ b ] || ! [ c ] )"
prop_checkSubshelledTests2 = verify checkSubshelledTests "( [ a ] )" prop_checkSubshelledTests2 = verify checkSubshelledTests "( [ a ] )"
prop_checkSubshelledTests3 = verify checkSubshelledTests "( [ a ] && [ b ] || test c )" prop_checkSubshelledTests3 = verify checkSubshelledTests "( [ a ] && [ b ] || test c )"
prop_checkSubshelledTests4 = verify checkSubshelledTests "( [ a ] && { [ b ] && [ c ]; } )" prop_checkSubshelledTests4 = verify checkSubshelledTests "( [ a ] && { [ b ] && [ c ]; } )"
prop_checkSubshelledTests5 = verifyNot checkSubshelledTests "( [[ ${var:=x} = y ]] )"
prop_checkSubshelledTests6 = verifyNot checkSubshelledTests "( [[ $((i++)) = 10 ]] )"
prop_checkSubshelledTests7 = verifyNot checkSubshelledTests "( [[ $((i+=1)) = 10 ]] )"
prop_checkSubshelledTests8 = verify checkSubshelledTests "# shellcheck disable=SC2234\nf() ( [[ x ]] )"
checkSubshelledTests params t = checkSubshelledTests params t =
case t of case t of
T_Subshell id list | all isTestStructure list -> T_Subshell id list | all isTestStructure list && (not (hasAssignment t)) ->
case () of case () of
-- Special case for if (test) and while (test) -- Special case for if (test) and while (test)
_ | isCompoundCondition (getPath (parentMap params) t) -> _ | isCompoundCondition (getPath (parentMap params) t) ->
style id 2233 "Remove superfluous (..) around condition." style id 2233 "Remove superfluous (..) around condition to avoid subshell overhead."
-- Special case for ([ x ]) -- Special case for ([ x ]), except for func() ( [ x ] )
_ | isSingleTest list -> _ | isSingleTest list && (not $ isFunctionBody (getPath (parentMap params) t)) ->
style id 2234 "Remove superfluous (..) around test command." style id 2234 "Remove superfluous (..) around test command to avoid subshell overhead."
-- General case for ([ x ] || [ y ] && etc) -- General case for ([ x ] || [ y ] && etc)
_ -> style id 2235 "Use { ..; } instead of (..) to avoid subshell overhead." _ -> style id 2235 "Use { ..; } instead of (..) to avoid subshell overhead."
@ -3768,6 +3774,11 @@ checkSubshelledTests params t =
[c] | isTestCommand c -> True [c] | isTestCommand c -> True
_ -> False _ -> False
isFunctionBody path =
case path of
(_:f:_) -> isFunction f
_ -> False
isTestStructure t = isTestStructure t =
case t of case t of
T_Banged _ t -> isTestStructure t T_Banged _ t -> isTestStructure t
@ -3798,6 +3809,19 @@ checkSubshelledTests params t =
T_UntilExpression {} : _ -> True T_UntilExpression {} : _ -> True
_ -> False _ -> False
hasAssignment t = isNothing $ doAnalysis guardNotAssignment t
guardNotAssignment t =
case t of
TA_Assignment {} -> Nothing
TA_Unary _ s _ -> guard . not $ "++" `isInfixOf` s || "--" `isInfixOf` s
T_DollarBraced _ _ l ->
let str = concat $ oversimplify l
modifier = getBracedModifier str
in
guard . not $ "=" `isPrefixOf` modifier || ":=" `isPrefixOf` modifier
T_DollarBraceCommandExpansion {} -> Nothing
_ -> Just ()
-- Skip any parent of a T_Subshell until we reach something interesting -- Skip any parent of a T_Subshell until we reach something interesting
skippable t = skippable t =
case t of case t of