Merge pull request #8110 from aakropotkin/quote-reserved

Quote reserved keywords when printing expressions

3 files changed, 24 insertions, 3 deletions

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index e2b455b91..0b4243670 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -94,7 +94,6 @@ RootValue allocRootValue(Value * v)
 #endif
 }
 
-
 void Value::print(const SymbolTable & symbols, std::ostream & str,
     std::set<const void *> * seen) const
 {
diff --git a/src/libexpr/print.cc b/src/libexpr/print.cc
index d08672cfc..53ba70bdd 100644
--- a/src/libexpr/print.cc
+++ b/src/libexpr/print.cc
@@ -1,4 +1,5 @@
 #include "print.hh"
+#include <unordered_set>
 
 namespace nix {
 
@@ -25,11 +26,26 @@ printLiteralBool(std::ostream & str, bool boolean)
     return str;
 }
 
+// Returns `true' is a string is a reserved keyword which requires quotation
+// when printing attribute set field names.
+//
+// This list should generally be kept in sync with `./lexer.l'.
+// You can test if a keyword needs to be added by running:
+//   $ nix eval --expr '{ <KEYWORD> = 1; }'
+// For example `or' doesn't need to be quoted.
+bool isReservedKeyword(const std::string_view str)
+{
+    static const std::unordered_set<std::string_view> reservedKeywords = {
+        "if", "then", "else", "assert", "with", "let", "in", "rec", "inherit"
+    };
+    return reservedKeywords.contains(str);
+}
+
 std::ostream &
 printIdentifier(std::ostream & str, std::string_view s) {
     if (s.empty())
         str << "\"\"";
-    else if (s == "if") // FIXME: handle other keywords
+    else if (isReservedKeyword(s))
         str << '"' << s << '"';
     else {
         char c = s[0];
@@ -50,10 +66,10 @@ printIdentifier(std::ostream & str, std::string_view s) {
     return str;
 }
 
-// FIXME: keywords
 static bool isVarName(std::string_view s)
 {
     if (s.size() == 0) return false;
+    if (isReservedKeyword(s)) return false;
     char c = s[0];
     if ((c >= '0' && c <= '9') || c == '-' || c == '\'') return false;
     for (auto & i : s)
diff --git a/src/libexpr/print.hh b/src/libexpr/print.hh
index f9cfc3964..3b72ae201 100644
--- a/src/libexpr/print.hh
+++ b/src/libexpr/print.hh
@@ -36,6 +36,12 @@ namespace nix {
     std::ostream & printAttributeName(std::ostream & o, std::string_view s);
 
     /**
+     * Returns `true' is a string is a reserved keyword which requires quotation
+     * when printing attribute set field names.
+     */
+    bool isReservedKeyword(const std::string_view str);
+
+    /**
      * Print a string as an identifier in the Nix expression language syntax.
      *
      * FIXME: "identifier" is ambiguous. Identifiers do not have a single