From 6d6c68c0d29310b6eca35f58b1e68f495d6cd33a Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Fri, 30 Nov 2007 16:48:45 +0000 Subject: * Added a new kind of multi-line string literal delimited by two single quotes. Example (from NixOS): job = '' start on network-interfaces start script rm -f /var/run/opengl-driver ${if videoDriver == "nvidia" then "ln -sf ${nvidiaDrivers} /var/run/opengl-driver" else if cfg.driSupport then "ln -sf ${mesa} /var/run/opengl-driver" else "" } rm -f /var/log/slim.log end script ''; This style has two big advantages: - \, ' and " aren't special, only '' and ${. So you get a lot less escaping in shell scripts / configuration files in Nixpkgs/NixOS. The delimiter '' is rare in scripts (and can usually be written as ""). ${ is also fairly rare. Other delimiters such as <<...>>, {{...}} and <|...|> were also considered but this one appears to have the fewest drawbacks (thanks Martin). - Indentation is intelligently stripped so that multi-line strings can follow the nesting structure of the containing Nix expression. E.g. in the example above 6 spaces are stripped from the start of each line. This prevents unnecessary indentation in generated files (which sometimes even breaks things). See tests/lang/eval-okay-ind-string.nix for some examples. --- src/libexpr/parser.y | 107 +++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 104 insertions(+), 3 deletions(-) (limited to 'src/libexpr/parser.y') diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y index 82b24cd07379..cd3ba88aa658 100644 --- a/src/libexpr/parser.y +++ b/src/libexpr/parser.y @@ -68,9 +68,100 @@ static Expr fixAttrs(int recursive, ATermList as) } +static Expr stripIndentation(ATermList es) +{ + if (es == ATempty) return makeStr(""); + + /* Figure out the minimum indentation. Note that by design + whitespace-only final lines are not taken into account. (So + the " " in "\n ''" is ignored, but the " " in "\n foo''" is.) */ + bool atStartOfLine = true; /* = seen only whitespace in the current line */ + unsigned int minIndent = 1000000; + unsigned int curIndent = 0; + ATerm e; + for (ATermIterator i(es); i; ++i) { + if (!matchIndStr(*i, e)) { + /* Anti-quotations end the current start-of-line whitespace. */ + if (atStartOfLine) { + atStartOfLine = false; + if (curIndent < minIndent) minIndent = curIndent; + } + continue; + } + string s = aterm2String(e); + for (unsigned int j = 0; j < s.size(); ++j) { + if (atStartOfLine) { + if (s[j] == ' ') + curIndent++; + else if (s[j] == '\n') { + /* Empty line, doesn't influence minimum + indentation. */ + curIndent = 0; + } else { + atStartOfLine = false; + if (curIndent < minIndent) minIndent = curIndent; + } + } else if (s[j] == '\n') { + atStartOfLine = true; + curIndent = 0; + } + } + } + + /* Strip spaces from each line. */ + ATermList es2 = ATempty; + atStartOfLine = true; + unsigned int curDropped = 0; + unsigned int n = ATgetLength(es); + for (ATermIterator i(es); i; ++i, --n) { + if (!matchIndStr(*i, e)) { + atStartOfLine = false; + curDropped = 0; + es2 = ATinsert(es2, *i); + continue; + } + + string s = aterm2String(e); + string s2; + for (unsigned int j = 0; j < s.size(); ++j) { + if (atStartOfLine) { + if (s[j] == ' ') { + if (curDropped++ >= minIndent) + s2 += s[j]; + } + else if (s[j] == '\n') { + curDropped = 0; + s2 += s[j]; + } else { + atStartOfLine = false; + curDropped = 0; + s2 += s[j]; + } + } else { + s2 += s[j]; + if (s[j] == '\n') atStartOfLine = true; + } + } + + /* Remove the last line if it is empty and consists only of + spaces. */ + if (n == 1) { + unsigned int p = s2.find_last_of('\n'); + if (p != string::npos && s2.find_first_not_of(' ', p + 1) == string::npos) + s2 = string(s2, 0, p + 1); + } + + es2 = ATinsert(es2, makeStr(s2)); + } + + return makeConcatStrings(ATreverse(es2)); +} + + void backToString(yyscan_t scanner); +void backToIndString(yyscan_t scanner); + - static Pos makeCurPos(YYLTYPE * loc, ParseData * data) { return makePos(toATerm(data->path), @@ -121,10 +212,11 @@ static void freeAndUnprotect(void * p) %type start expr expr_function expr_if expr_op %type expr_app expr_select expr_simple bind inheritsrc formal -%type binds ids expr_list formals string_parts -%token ID INT STR PATH URI +%type binds ids expr_list formals string_parts ind_string_parts +%token ID INT STR IND_STR PATH URI %token IF THEN ELSE ASSERT WITH LET IN REC INHERIT EQ NEQ AND OR IMPL %token DOLLAR_CURLY /* == ${ */ +%token IND_STRING_OPEN IND_STRING_CLOSE %nonassoc IMPL %left OR @@ -199,6 +291,9 @@ expr_simple else if (ATgetNext($2) == ATempty) $$ = ATgetFirst($2); else $$ = makeConcatStrings(ATreverse($2)); } + | IND_STRING_OPEN ind_string_parts IND_STRING_CLOSE { + $$ = stripIndentation(ATreverse($2)); + } | PATH { $$ = makePath(toATerm(absPath(aterm2String($1), data->basePath))); } | URI { $$ = makeStr($1, ATempty); } | '(' expr ')' { $$ = $2; } @@ -219,6 +314,12 @@ string_parts | { $$ = ATempty; } ; +ind_string_parts + : ind_string_parts IND_STR { $$ = ATinsert($1, $2); } + | ind_string_parts DOLLAR_CURLY expr '}' { backToIndString(scanner); $$ = ATinsert($1, $3); } + | { $$ = ATempty; } + ; + binds : binds bind { $$ = ATinsert($1, $2); } | { $$ = ATempty; } -- cgit 1.4.1