t/chainlint.sed - jrn/git - Git at Google

 #------------------------------------------------------------------------------
 # Detect broken &&-chains in tests.
 #
 # At present, only &&-chains in subshells are examined by this linter;
 # top-level &&-chains are instead checked directly by the test framework. Like
 # the top-level &&-chain linter, the subshell linter (intentionally) does not
 # check &&-chains within {...} blocks.
 #
 # Checking for &&-chain breakage is done line-by-line by pure textual
 # inspection.
 #
 # Incomplete lines (those ending with "\") are stitched together with following
 # lines to simplify processing, particularly of "one-liner" statements.
 # Top-level here-docs are swallowed to avoid false positives within the
 # here-doc body, although the statement to which the here-doc is attached is
 # retained.
 #
 # Heuristics are used to detect end-of-subshell when the closing ")" is cuddled
 # with the final subshell statement on the same line:
 #
 #    (cd foo &&
 #        bar)
 #
 # in order to avoid misinterpreting the ")" in constructs such as "x=$(...)"
 # and "case $x in *)" as ending the subshell.
 #
 # Lines missing a final "&&" are flagged with "?!AMP?!", as are lines which
 # chain commands with ";" internally rather than "&&". A line may be flagged
 # for both violations.
 #
 # Detection of a missing &&-link in a multi-line subshell is complicated by the
 # fact that the last statement before the closing ")" must not end with "&&".
 # Since processing is line-by-line, it is not known whether a missing "&&" is
 # legitimate or not until the _next_ line is seen. To accommodate this, within
 # multi-line subshells, each line is stored in sed's "hold" area until after
 # the next line is seen and processed. If the next line is a stand-alone ")",
 # then a missing "&&" on the previous line is legitimate; otherwise a missing
 # "&&" is a break in the &&-chain.
 #
 #    (
 #         cd foo &&
 #         bar
 #    )
 #
 # In practical terms, when "bar" is encountered, it is flagged with "?!AMP?!",
 # but when the stand-alone ")" line is seen which closes the subshell, the
 # "?!AMP?!" violation is removed from the "bar" line (retrieved from the "hold"
 # area) since the final statement of a subshell must not end with "&&". The
 # final line of a subshell may still break the &&-chain by using ";" internally
 # to chain commands together rather than "&&", but an internal "?!AMP?!" is
 # never removed from a line even though a line-ending "?!AMP?!" might be.
 #
 # Care is taken to recognize the last _statement_ of a multi-line subshell, not
 # necessarily the last textual _line_ within the subshell, since &&-chaining
 # applies to statements, not to lines. Consequently, blank lines, comment
 # lines, and here-docs are swallowed (but not the command to which the here-doc
 # is attached), leaving the last statement in the "hold" area, not the last
 # line, thus simplifying &&-link checking.
 #
 # The final statement before "done" in for- and while-loops, and before "elif",
 # "else", and "fi" in if-then-else likewise must not end with "&&", thus
 # receives similar treatment.
 #
 # Swallowing here-docs with arbitrary tags requires a bit of finesse. When a
 # line such as "cat <<EOF" is seen, the here-doc tag is copied to the front of
 # the line enclosed in angle brackets as a sentinel, giving "<EOF>cat <<EOF".
 # As each subsequent line is read, it is appended to the target line and a
 # (whitespace-loose) back-reference match /^<(.*)>\n\1$/ is attempted to see if
 # the content inside "<...>" matches the entirety of the newly-read line. For
 # instance, if the next line read is "some data", when concatenated with the
 # target line, it becomes "<EOF>cat <<EOF\nsome data", and a match is attempted
 # to see if "EOF" matches "some data". Since it doesn't, the next line is
 # attempted. When a line consisting of only "EOF" (and possible whitespace) is
 # encountered, it is appended to the target line giving "<EOF>cat <<EOF\nEOF",
 # in which case the "EOF" inside "<...>" does match the text following the
 # newline, thus the closing here-doc tag has been found. The closing tag line
 # and the "<...>" prefix on the target line are then discarded, leaving just
 # the target line "cat <<EOF".
 #------------------------------------------------------------------------------

 # incomplete line -- slurp up next line
 :squash
 /\\$/ {
 	N
 	s/\\\n//
 	bsquash
 }

 # here-doc -- swallow it to avoid false hits within its body (but keep the
 # command to which it was attached)
 /<<-*[ 	]*[\\'"]*[A-Za-z0-9_]/ {
 	/"[^"]*<<[^"]*"/bnotdoc
 	s/^\(.*<<-*[ 	]*\)[\\'"]*\([A-Za-z0-9_][A-Za-z0-9_]*\)['"]*/<\2>\1\2/
 	:hered
 	N
 	/^<\([^>]*\)>.*\n[ 	]*\1[ 	]*$/!{
 		s/\n.*$//
 		bhered
 	}
 	s/^<[^>]*>//
 	s/\n.*$//
 }
 :notdoc

 # one-liner "(...) &&"
 /^[ 	]*!*[ 	]*(..*)[ 	]*&&[ 	]*$/boneline

 # same as above but without trailing "&&"
 /^[ 	]*!*[ 	]*(..*)[ 	]*$/boneline

 # one-liner "(...) >x" (or "2>x" or "<x" or "|x" or "&"
 /^[ 	]*!*[ 	]*(..*)[ 	]*[0-9]*[<>|&]/boneline

 # multi-line "(...\n...)"
 /^[ 	]*(/bsubsh

 # innocuous line -- print it and advance to next line
 b

 # found one-liner "(...)" -- mark suspect if it uses ";" internally rather than
 # "&&" (but not ";" in a string)
 :oneline
 /;/{
 	/"[^"]*;[^"]*"/!s/;/; ?!AMP?!/
 }
 b

 :subsh
 # bare "(" line? -- stash for later printing
 /^[ 	]*([	]*$/ {
 	h
 	bnextln
 }
 # "(..." line -- "(" opening subshell cuddled with command; temporarily replace
 # "(" with sentinel "^" and process the line as if "(" had been seen solo on
 # the preceding line; this temporary replacement prevents several rules from
 # accidentally thinking "(" introduces a nested subshell; "^" is changed back
 # to "(" at output time
 x
 s/.*//
 x
 s/(/^/
 bslurp

 :nextln
 N
 s/.*\n//

 :slurp
 # incomplete line "...\"
 /\\$/bicmplte
 # multi-line quoted string "...\n..."?
 /"/bdqstr
 # multi-line quoted string '...\n...'? (but not contraction in string "it's")
 /'/{
 	/"[^'"]*'[^'"]*"/!bsqstr
 }
 :folded
 # here-doc -- swallow it (but not "<<" in a string)
 /<<-*[ 	]*[\\'"]*[A-Za-z0-9_]/{
 	/"[^"]*<<[^"]*"/!bheredoc
 }
 # comment or empty line -- discard since final non-comment, non-empty line
 # before closing ")", "done", "elsif", "else", or "fi" will need to be
 # re-visited to drop "suspect" marking since final line of those constructs
 # legitimately lacks "&&", so "suspect" mark must be removed
 /^[ 	]*#/bnextln
 /^[ 	]*$/bnextln
 # in-line comment -- strip it (but not "#" in a string, Bash ${#...} array
 # length, or Perforce "//depot/path#42" revision in filespec)
 /[ 	]#/{
 	/"[^"]*#[^"]*"/!s/[ 	]#.*$//
 }
 # one-liner "case ... esac"
 /^[ 	^]*case[ 	]*..*esac/bchkchn
 # multi-line "case ... esac"
 /^[ 	^]*case[ 	]..*[ 	]in/bcase
 # multi-line "for ... done" or "while ... done"
 /^[ 	^]*for[ 	]..*[ 	]in/bcont
 /^[ 	^]*while[ 	]/bcont
 /^[ 	]*do[ 	]/bcont
 /^[ 	]*do[ 	]*$/bcont
 /;[ 	]*do/bcont
 /^[ 	]*done[ 	]*&&[ 	]*$/bdone
 /^[ 	]*done[ 	]*$/bdone
 /^[ 	]*done[ 	]*[<>|]/bdone
 /^[ 	]*done[ 	]*)/bdone
 /||[ 	]*exit[ 	]/bcont
 /||[ 	]*exit[ 	]*$/bcont
 # multi-line "if...elsif...else...fi"
 /^[ 	^]*if[ 	]/bcont
 /^[ 	]*then[ 	]/bcont
 /^[ 	]*then[ 	]*$/bcont
 /;[ 	]*then/bcont
 /^[ 	]*elif[ 	]/belse
 /^[ 	]*elif[ 	]*$/belse
 /^[ 	]*else[ 	]/belse
 /^[ 	]*else[ 	]*$/belse
 /^[ 	]*fi[ 	]*&&[ 	]*$/bdone
 /^[ 	]*fi[ 	]*$/bdone
 /^[ 	]*fi[ 	]*[<>|]/bdone
 /^[ 	]*fi[ 	]*)/bdone
 # nested one-liner "(...) &&"
 /^[ 	^]*(.*)[ 	]*&&[ 	]*$/bchkchn
 # nested one-liner "(...)"
 /^[ 	^]*(.*)[ 	]*$/bchkchn
 # nested one-liner "(...) >x" (or "2>x" or "<x" or "|x")
 /^[ 	^]*(.*)[ 	]*[0-9]*[<>|]/bchkchn
 # nested multi-line "(...\n...)"
 /^[ 	^]*(/bnest
 # multi-line "{...\n...}"
 /^[ 	^]*{/bblock
 # closing ")" on own line -- exit subshell
 /^[ 	]*)/bclssolo
 # "$((...))" -- arithmetic expansion; not closing ")"
 /\$(([^)][^)]*))[^)]*$/bchkchn
 # "$(...)" -- command substitution; not closing ")"
 /\$([^)][^)]*)[^)]*$/bchkchn
 # multi-line "$(...\n...)" -- command substitution; treat as nested subshell
 /\$([^)]*$/bnest
 # "=(...)" -- Bash array assignment; not closing ")"
 /=(/bchkchn
 # closing "...) &&"
 /)[ 	]*&&[ 	]*$/bclose
 # closing "...)"
 /)[ 	]*$/bclose
 # closing "...) >x" (or "2>x" or "<x" or "|x")
 /)[ 	]*[<>|]/bclose
 :chkchn
 # mark suspect if line uses ";" internally rather than "&&" (but not ";" in a
 # string and not ";;" in one-liner "case...esac")
 /;/{
 	/;;/!{
 		/"[^"]*;[^"]*"/!s/;/; ?!AMP?!/
 	}
 }
 # line ends with pipe "...|" -- valid; not missing "&&"
 /|[ 	]*$/bcont
 # missing end-of-line "&&" -- mark suspect
 /&&[ 	]*$/!s/$/ ?!AMP?!/
 :cont
 # retrieve and print previous line
 x
 s/^\([ 	]*\)^/\1(/
 s/?!HERE?!/<</g
 n
 bslurp

 # found incomplete line "...\" -- slurp up next line
 :icmplte
 N
 s/\\\n//
 bslurp

 # check for multi-line double-quoted string "...\n..." -- fold to one line
 :dqstr
 # remove all quote pairs
 s/"\([^"]*\)"/@!\1@!/g
 # done if no dangling quote
 /"/!bdqdone
 # otherwise, slurp next line and try again
 N
 s/\n//
 bdqstr
 :dqdone
 s/@!/"/g
 bfolded

 # check for multi-line single-quoted string '...\n...' -- fold to one line
 :sqstr
 # remove all quote pairs
 s/'\([^']*\)'/@!\1@!/g
 # done if no dangling quote
 /'/!bsqdone
 # otherwise, slurp next line and try again
 N
 s/\n//
 bsqstr
 :sqdone
 s/@!/'/g
 bfolded

 # found here-doc -- swallow it to avoid false hits within its body (but keep
 # the command to which it was attached)
 :heredoc
 s/^\(.*\)<<\(-*[ 	]*\)[\\'"]*\([A-Za-z0-9_][A-Za-z0-9_]*\)['"]*/<\3>\1?!HERE?!\2\3/
 :hdocsub
 N
 /^<\([^>]*\)>.*\n[ 	]*\1[ 	]*$/!{
 	s/\n.*$//
 	bhdocsub
 }
 s/^<[^>]*>//
 s/\n.*$//
 bfolded

 # found "case ... in" -- pass through untouched
 :case
 x
 s/^\([ 	]*\)^/\1(/
 s/?!HERE?!/<</g
 n
 :cascom
 /^[ 	]*#/{
 	N
 	s/.*\n//
 	bcascom
 }
 /^[ 	]*esac/bslurp
 bcase

 # found "else" or "elif" -- drop "suspect" from final line before "else" since
 # that line legitimately lacks "&&"
 :else
 x
 s/\( ?!AMP?!\)* ?!AMP?!$//
 x
 bcont

 # found "done" closing for-loop or while-loop, or "fi" closing if-then -- drop
 # "suspect" from final contained line since that line legitimately lacks "&&"
 :done
 x
 s/\( ?!AMP?!\)* ?!AMP?!$//
 x
 # is 'done' or 'fi' cuddled with ")" to close subshell?
 /done.*)/bclose
 /fi.*)/bclose
 bchkchn

 # found nested multi-line "(...\n...)" -- pass through untouched
 :nest
 x
 :nstslrp
 s/^\([ 	]*\)^/\1(/
 s/?!HERE?!/<</g
 n
 :nstcom
 # comment -- not closing ")" if in comment
 /^[ 	]*#/{
 	N
 	s/.*\n//
 	bnstcom
 }
 # closing ")" on own line -- stop nested slurp
 /^[ 	]*)/bnstcl
 # "$((...))" -- arithmetic expansion; not closing ")"
 /\$(([^)][^)]*))[^)]*$/bnstcnt
 # "$(...)" -- command substitution; not closing ")"
 /\$([^)][^)]*)[^)]*$/bnstcnt
 # closing "...)" -- stop nested slurp
 /)/bnstcl
 :nstcnt
 x
 bnstslrp
 :nstcl
 # is it "))" which closes nested and parent subshells?
 /)[ 	]*)/bslurp
 bchkchn

 # found multi-line "{...\n...}" block -- pass through untouched
 :block
 x
 s/^\([ 	]*\)^/\1(/
 s/?!HERE?!/<</g
 n
 :blkcom
 /^[ 	]*#/{
 	N
 	s/.*\n//
 	bblkcom
 }
 # closing "}" -- stop block slurp
 /}/bchkchn
 bblock

 # found closing ")" on own line -- drop "suspect" from final line of subshell
 # since that line legitimately lacks "&&" and exit subshell loop
 :clssolo
 x
 s/\( ?!AMP?!\)* ?!AMP?!$//
 s/^\([ 	]*\)^/\1(/
 s/?!HERE?!/<</g
 p
 x
 s/^\([ 	]*\)^/\1(/
 s/?!HERE?!/<</g
 b

 # found closing "...)" -- exit subshell loop
 :close
 x
 s/^\([ 	]*\)^/\1(/
 s/?!HERE?!/<</g
 p
 x
 s/^\([ 	]*\)^/\1(/
 s/?!HERE?!/<</g
 b
	#------------------------------------------------------------------------------
	# Detect broken &&-chains in tests.
	#
	# At present, only &&-chains in subshells are examined by this linter;
	# top-level &&-chains are instead checked directly by the test framework. Like
	# the top-level &&-chain linter, the subshell linter (intentionally) does not
	# check &&-chains within {...} blocks.
	#
	# Checking for &&-chain breakage is done line-by-line by pure textual
	# inspection.
	#
	# Incomplete lines (those ending with "\") are stitched together with following
	# lines to simplify processing, particularly of "one-liner" statements.
	# Top-level here-docs are swallowed to avoid false positives within the
	# here-doc body, although the statement to which the here-doc is attached is
	# retained.
	#
	# Heuristics are used to detect end-of-subshell when the closing ")" is cuddled
	# with the final subshell statement on the same line:
	#
	# (cd foo &&
	# bar)
	#
	# in order to avoid misinterpreting the ")" in constructs such as "x=$(...)"
	# and "case $x in *)" as ending the subshell.
	#
	# Lines missing a final "&&" are flagged with "?!AMP?!", as are lines which
	# chain commands with ";" internally rather than "&&". A line may be flagged
	# for both violations.
	#
	# Detection of a missing &&-link in a multi-line subshell is complicated by the
	# fact that the last statement before the closing ")" must not end with "&&".
	# Since processing is line-by-line, it is not known whether a missing "&&" is
	# legitimate or not until the _next_ line is seen. To accommodate this, within
	# multi-line subshells, each line is stored in sed's "hold" area until after
	# the next line is seen and processed. If the next line is a stand-alone ")",
	# then a missing "&&" on the previous line is legitimate; otherwise a missing
	# "&&" is a break in the &&-chain.
	#
	# (
	# cd foo &&
	# bar
	# )
	#
	# In practical terms, when "bar" is encountered, it is flagged with "?!AMP?!",
	# but when the stand-alone ")" line is seen which closes the subshell, the
	# "?!AMP?!" violation is removed from the "bar" line (retrieved from the "hold"
	# area) since the final statement of a subshell must not end with "&&". The
	# final line of a subshell may still break the &&-chain by using ";" internally
	# to chain commands together rather than "&&", but an internal "?!AMP?!" is
	# never removed from a line even though a line-ending "?!AMP?!" might be.
	#
	# Care is taken to recognize the last _statement_ of a multi-line subshell, not
	# necessarily the last textual _line_ within the subshell, since &&-chaining
	# applies to statements, not to lines. Consequently, blank lines, comment
	# lines, and here-docs are swallowed (but not the command to which the here-doc
	# is attached), leaving the last statement in the "hold" area, not the last
	# line, thus simplifying &&-link checking.
	#
	# The final statement before "done" in for- and while-loops, and before "elif",
	# "else", and "fi" in if-then-else likewise must not end with "&&", thus
	# receives similar treatment.
	#
	# Swallowing here-docs with arbitrary tags requires a bit of finesse. When a
	# line such as "cat <<EOF" is seen, the here-doc tag is copied to the front of
	# the line enclosed in angle brackets as a sentinel, giving "<EOF>cat <<EOF".
	# As each subsequent line is read, it is appended to the target line and a
	# (whitespace-loose) back-reference match /^<(.*)>\n\1$/ is attempted to see if
	# the content inside "<...>" matches the entirety of the newly-read line. For
	# instance, if the next line read is "some data", when concatenated with the
	# target line, it becomes "<EOF>cat <<EOF\nsome data", and a match is attempted
	# to see if "EOF" matches "some data". Since it doesn't, the next line is
	# attempted. When a line consisting of only "EOF" (and possible whitespace) is
	# encountered, it is appended to the target line giving "<EOF>cat <<EOF\nEOF",
	# in which case the "EOF" inside "<...>" does match the text following the
	# newline, thus the closing here-doc tag has been found. The closing tag line
	# and the "<...>" prefix on the target line are then discarded, leaving just
	# the target line "cat <<EOF".
	#------------------------------------------------------------------------------

	# incomplete line -- slurp up next line
	:squash
	/\\$/ {
	N
	s/\\\n//
	bsquash
	}

	# here-doc -- swallow it to avoid false hits within its body (but keep the
	# command to which it was attached)
	/<<-[ ][\\'"]*[A-Za-z0-9_]/ {
	/"[^"]<<[^"]"/bnotdoc
	s/^\(.<<-[ ]\)[\\'"]\([A-Za-z0-9_][A-Za-z0-9_]\)['"]/<\2>\1\2/
	:hered
	N
	/^<\([^>]\)>.\n[ ]\1[ ]$/!{
	s/\n.*$//
	bhered
	}
	s/^<[^>]*>//
	s/\n.*$//
	}
	:notdoc

	# one-liner "(...) &&"
	/^[ ]![ ](..)[ ]&&[ ]$/boneline

	# same as above but without trailing "&&"
	/^[ ]![ ](..)[ ]*$/boneline

	# one-liner "(...) >x" (or "2>x" or "<x" or "\|x" or "&"
	/^[ ]![ ](..)[ ][0-9][<>\|&]/boneline

	# multi-line "(...\n...)"
	/^[ ]*(/bsubsh

	# innocuous line -- print it and advance to next line
	b

	# found one-liner "(...)" -- mark suspect if it uses ";" internally rather than
	# "&&" (but not ";" in a string)
	:oneline
	/;/{
	/"[^"];[^"]"/!s/;/; ?!AMP?!/
	}
	b

	:subsh
	# bare "(" line? -- stash for later printing
	/^[ ]([ ]$/ {
	h
	bnextln
	}
	# "(..." line -- "(" opening subshell cuddled with command; temporarily replace
	# "(" with sentinel "^" and process the line as if "(" had been seen solo on
	# the preceding line; this temporary replacement prevents several rules from
	# accidentally thinking "(" introduces a nested subshell; "^" is changed back
	# to "(" at output time
	x
	s/.*//
	x
	s/(/^/
	bslurp

	:nextln
	N
	s/.*\n//

	:slurp
	# incomplete line "...\"
	/\\$/bicmplte
	# multi-line quoted string "...\n..."?
	/"/bdqstr
	# multi-line quoted string '...\n...'? (but not contraction in string "it's")
	/'/{
	/"[^'"]'[^'"]"/!bsqstr
	}
	:folded
	# here-doc -- swallow it (but not "<<" in a string)
	/<<-[ ][\\'"]*[A-Za-z0-9_]/{
	/"[^"]<<[^"]"/!bheredoc
	}
	# comment or empty line -- discard since final non-comment, non-empty line
	# before closing ")", "done", "elsif", "else", or "fi" will need to be
	# re-visited to drop "suspect" marking since final line of those constructs
	# legitimately lacks "&&", so "suspect" mark must be removed
	/^[ ]*#/bnextln
	/^[ ]*$/bnextln
	# in-line comment -- strip it (but not "#" in a string, Bash ${#...} array
	# length, or Perforce "//depot/path#42" revision in filespec)
	/[ ]#/{
	/"[^"]#[^"]"/!s/[ ]#.*$//
	}
	# one-liner "case ... esac"
	/^[ ^]case[ ]..*esac/bchkchn
	# multi-line "case ... esac"
	/^[ ^]case[ ]..[ ]in/bcase
	# multi-line "for ... done" or "while ... done"
	/^[ ^]for[ ]..[ ]in/bcont
	/^[ ^]*while[ ]/bcont
	/^[ ]*do[ ]/bcont
	/^[ ]do[ ]$/bcont
	/;[ ]*do/bcont
	/^[ ]done[ ]&&[ ]*$/bdone
	/^[ ]done[ ]$/bdone
	/^[ ]done[ ][<>\|]/bdone
	/^[ ]done[ ])/bdone
	/\|\|[ ]*exit[ ]/bcont
	/\|\|[ ]exit[ ]$/bcont
	# multi-line "if...elsif...else...fi"
	/^[ ^]*if[ ]/bcont
	/^[ ]*then[ ]/bcont
	/^[ ]then[ ]$/bcont
	/;[ ]*then/bcont
	/^[ ]*elif[ ]/belse
	/^[ ]elif[ ]$/belse
	/^[ ]*else[ ]/belse
	/^[ ]else[ ]$/belse
	/^[ ]fi[ ]&&[ ]*$/bdone
	/^[ ]fi[ ]$/bdone
	/^[ ]fi[ ][<>\|]/bdone
	/^[ ]fi[ ])/bdone
	# nested one-liner "(...) &&"
	/^[ ^](.)[ ]&&[ ]$/bchkchn
	# nested one-liner "(...)"
	/^[ ^](.)[ ]*$/bchkchn
	# nested one-liner "(...) >x" (or "2>x" or "<x" or "\|x")
	/^[ ^](.)[ ][0-9][<>\|]/bchkchn
	# nested multi-line "(...\n...)"
	/^[ ^]*(/bnest
	# multi-line "{...\n...}"
	/^[ ^]*{/bblock
	# closing ")" on own line -- exit subshell
	/^[ ]*)/bclssolo
	# "$((...))" -- arithmetic expansion; not closing ")"
	/\$(([^)][^)]))[^)]$/bchkchn
	# "$(...)" -- command substitution; not closing ")"
	/\$([^)][^)])[^)]$/bchkchn
	# multi-line "$(...\n...)" -- command substitution; treat as nested subshell
	/\$([^)]*$/bnest
	# "=(...)" -- Bash array assignment; not closing ")"
	/=(/bchkchn
	# closing "...) &&"
	/)[ ]&&[ ]$/bclose
	# closing "...)"
	/)[ ]*$/bclose
	# closing "...) >x" (or "2>x" or "<x" or "\|x")
	/)[ ]*[<>\|]/bclose
	:chkchn
	# mark suspect if line uses ";" internally rather than "&&" (but not ";" in a
	# string and not ";;" in one-liner "case...esac")
	/;/{
	/;;/!{
	/"[^"];[^"]"/!s/;/; ?!AMP?!/
	}
	}
	# line ends with pipe "...\|" -- valid; not missing "&&"
	/\|[ ]*$/bcont
	# missing end-of-line "&&" -- mark suspect
	/&&[ ]*$/!s/$/ ?!AMP?!/
	:cont
	# retrieve and print previous line
	x
	s/^\([ ]*\)^/\1(/
	s/?!HERE?!/<</g
	n
	bslurp

	# found incomplete line "...\" -- slurp up next line
	:icmplte
	N
	s/\\\n//
	bslurp

	# check for multi-line double-quoted string "...\n..." -- fold to one line
	:dqstr
	# remove all quote pairs
	s/"\([^"]*\)"/@!\1@!/g
	# done if no dangling quote
	/"/!bdqdone
	# otherwise, slurp next line and try again
	N
	s/\n//
	bdqstr
	:dqdone
	s/@!/"/g
	bfolded

	# check for multi-line single-quoted string '...\n...' -- fold to one line
	:sqstr
	# remove all quote pairs
	s/'\([^']*\)'/@!\1@!/g
	# done if no dangling quote
	/'/!bsqdone
	# otherwise, slurp next line and try again
	N
	s/\n//
	bsqstr
	:sqdone
	s/@!/'/g
	bfolded

	# found here-doc -- swallow it to avoid false hits within its body (but keep
	# the command to which it was attached)
	:heredoc
	s/^\(.\)<<\(-[ ]\)[\\'"]\([A-Za-z0-9_][A-Za-z0-9_]\)['"]/<\3>\1?!HERE?!\2\3/
	:hdocsub
	N
	/^<\([^>]\)>.\n[ ]\1[ ]$/!{
	s/\n.*$//
	bhdocsub
	}
	s/^<[^>]*>//
	s/\n.*$//
	bfolded

	# found "case ... in" -- pass through untouched
	:case
	x
	s/^\([ ]*\)^/\1(/
	s/?!HERE?!/<</g
	n
	:cascom
	/^[ ]*#/{
	N
	s/.*\n//
	bcascom
	}
	/^[ ]*esac/bslurp
	bcase

	# found "else" or "elif" -- drop "suspect" from final line before "else" since
	# that line legitimately lacks "&&"
	:else
	x
	s/\( ?!AMP?!\)* ?!AMP?!$//
	x
	bcont

	# found "done" closing for-loop or while-loop, or "fi" closing if-then -- drop
	# "suspect" from final contained line since that line legitimately lacks "&&"
	:done
	x
	s/\( ?!AMP?!\)* ?!AMP?!$//
	x
	# is 'done' or 'fi' cuddled with ")" to close subshell?
	/done.*)/bclose
	/fi.*)/bclose
	bchkchn

	# found nested multi-line "(...\n...)" -- pass through untouched
	:nest
	x
	:nstslrp
	s/^\([ ]*\)^/\1(/
	s/?!HERE?!/<</g
	n
	:nstcom
	# comment -- not closing ")" if in comment
	/^[ ]*#/{
	N
	s/.*\n//
	bnstcom
	}
	# closing ")" on own line -- stop nested slurp
	/^[ ]*)/bnstcl
	# "$((...))" -- arithmetic expansion; not closing ")"
	/\$(([^)][^)]))[^)]$/bnstcnt
	# "$(...)" -- command substitution; not closing ")"
	/\$([^)][^)])[^)]$/bnstcnt
	# closing "...)" -- stop nested slurp
	/)/bnstcl
	:nstcnt
	x
	bnstslrp
	:nstcl
	# is it "))" which closes nested and parent subshells?
	/)[ ]*)/bslurp
	bchkchn

	# found multi-line "{...\n...}" block -- pass through untouched
	:block
	x
	s/^\([ ]*\)^/\1(/
	s/?!HERE?!/<</g
	n
	:blkcom
	/^[ ]*#/{
	N
	s/.*\n//
	bblkcom
	}
	# closing "}" -- stop block slurp
	/}/bchkchn
	bblock

	# found closing ")" on own line -- drop "suspect" from final line of subshell
	# since that line legitimately lacks "&&" and exit subshell loop
	:clssolo
	x
	s/\( ?!AMP?!\)* ?!AMP?!$//
	s/^\([ ]*\)^/\1(/
	s/?!HERE?!/<</g
	p
	x
	s/^\([ ]*\)^/\1(/
	s/?!HERE?!/<</g
	b

	# found closing "...)" -- exit subshell loop
	:close
	x
	s/^\([ ]*\)^/\1(/
	s/?!HERE?!/<</g
	p
	x
	s/^\([ ]*\)^/\1(/
	s/?!HERE?!/<</g
	b