Move `escapeString` to its own file

Change-Id: Ie5c954ec73c46c9d3c679ef99a83a29cc7a08352

9 files changed, 140 insertions, 73 deletions

diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index fd380935a..72a8764e6 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -4,6 +4,7 @@
 #include "symbol-table.hh"
 #include "util.hh"
 #include "print.hh"
+#include "escape-string.hh"
 
 #include <cstdlib>
 
@@ -36,7 +37,7 @@ void ExprFloat::show(const SymbolTable & symbols, std::ostream & str) const
 
 void ExprString::show(const SymbolTable & symbols, std::ostream & str) const
 {
-    printLiteralString(str, s);
+    escapeString(str, s);
 }
 
 void ExprPath::show(const SymbolTable & symbols, std::ostream & str) const
diff --git a/src/libexpr/print-ambiguous.cc b/src/libexpr/print-ambiguous.cc
index 3f3c2c45a..ec30f5073 100644
--- a/src/libexpr/print-ambiguous.cc
+++ b/src/libexpr/print-ambiguous.cc
@@ -2,6 +2,7 @@
 #include "print.hh"
 #include "eval.hh"
 #include "signals.hh"
+#include "escape-string.hh"
 
 namespace nix {
 
@@ -27,7 +28,7 @@ void printAmbiguous(
         printLiteralBool(str, v.boolean);
         break;
     case nString:
-        printLiteralString(str, v.string.s);
+        escapeString(str, v.string.s);
         break;
     case nPath:
         str << v.path().to_string(); // !!! escaping?
diff --git a/src/libexpr/print.cc b/src/libexpr/print.cc
index 43e366d08..e5e6b9b21 100644
--- a/src/libexpr/print.cc
+++ b/src/libexpr/print.cc
@@ -2,6 +2,7 @@
 #include <span>
 #include <unordered_set>
 
+#include "escape-string.hh"
 #include "print.hh"
 #include "ansicolor.hh"
 #include "store-api.hh"
@@ -11,57 +12,6 @@
 
 namespace nix {
 
-void printElided(
-    std::ostream & output,
-    unsigned int value,
-    const std::string_view single,
-    const std::string_view plural,
-    bool ansiColors)
-{
-    if (ansiColors)
-        output << ANSI_FAINT;
-    output << "«";
-    pluralize(output, value, single, plural);
-    output << " elided»";
-    if (ansiColors)
-        output << ANSI_NORMAL;
-}
-
-
-std::ostream &
-printLiteralString(std::ostream & str, const std::string_view string, size_t maxLength, bool ansiColors)
-{
-    size_t charsPrinted = 0;
-    if (ansiColors)
-        str << ANSI_MAGENTA;
-    str << "\"";
-    for (auto i = string.begin(); i != string.end(); ++i) {
-        if (charsPrinted >= maxLength) {
-            str << "\" ";
-            printElided(str, string.length() - charsPrinted, "byte", "bytes", ansiColors);
-            return str;
-        }
-
-        if (*i == '\"' || *i == '\\') str << "\\" << *i;
-        else if (*i == '\n') str << "\\n";
-        else if (*i == '\r') str << "\\r";
-        else if (*i == '\t') str << "\\t";
-        else if (*i == '$' && *(i+1) == '{') str << "\\" << *i;
-        else str << *i;
-        charsPrinted++;
-    }
-    str << "\"";
-    if (ansiColors)
-        str << ANSI_NORMAL;
-    return str;
-}
-
-std::ostream &
-printLiteralString(std::ostream & str, const std::string_view string)
-{
-    return printLiteralString(str, string, std::numeric_limits<size_t>::max(), false);
-}
-
 std::ostream &
 printLiteralBool(std::ostream & str, bool boolean)
 {
@@ -93,7 +43,7 @@ printIdentifier(std::ostream & str, std::string_view s) {
     else {
         char c = s[0];
         if (!((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_')) {
-            printLiteralString(str, s);
+            escapeString(str, s);
             return str;
         }
         for (auto c : s)
@@ -101,7 +51,7 @@ printIdentifier(std::ostream & str, std::string_view s) {
                   (c >= 'A' && c <= 'Z') ||
                   (c >= '0' && c <= '9') ||
                   c == '_' || c == '\'' || c == '-')) {
-                printLiteralString(str, s);
+                escapeString(str, s);
                 return str;
             }
         str << s;
@@ -129,7 +79,7 @@ printAttributeName(std::ostream & str, std::string_view name) {
     if (isVarName(name))
         str << name;
     else
-        printLiteralString(str, name);
+        escapeString(str, name);
     return str;
 }
 
@@ -248,7 +198,13 @@ private:
 
     void printString(Value & v)
     {
-        printLiteralString(output, v.string.s, options.maxStringLength, options.ansiColors);
+        // NB: Non-printing characters won't be escaped.
+        escapeString(
+            output,
+            v.string.s,
+            options.maxStringLength,
+            options.ansiColors
+        );
     }
 
     void printPath(Value & v)
diff --git a/src/libexpr/print.hh b/src/libexpr/print.hh
index 94cb11ca7..42826d94d 100644
--- a/src/libexpr/print.hh
+++ b/src/libexpr/print.hh
@@ -11,28 +11,13 @@
 
 #include "fmt.hh"
 #include "print-options.hh"
+#include "print-elided.hh"
 
 namespace nix {
 
 class EvalState;
 struct Value;
 
-/**
- * Print a string as a Nix string literal.
- *
- * Quotes and fairly minimal escaping are added.
- *
- * @param o The output stream to print to
- * @param s The logical string
- */
-std::ostream & printLiteralString(std::ostream & o, std::string_view s);
-inline std::ostream & printLiteralString(std::ostream & o, const char * s) {
-    return printLiteralString(o, std::string_view(s));
-}
-inline std::ostream & printLiteralString(std::ostream & o, const std::string & s) {
-    return printLiteralString(o, std::string_view(s));
-}
-
 /** Print `true` or `false`. */
 std::ostream & printLiteralBool(std::ostream & o, bool b);
 
diff --git a/src/libutil/escape-string.cc b/src/libutil/escape-string.cc
new file mode 100644
index 000000000..8160403cd
--- /dev/null
+++ b/src/libutil/escape-string.cc
@@ -0,0 +1,40 @@
+#include <iomanip>
+#include <ostream>
+#include <sstream>
+
+#include "ansicolor.hh"
+#include "escape-char.hh"
+#include "english.hh"
+#include "escape-string.hh"
+#include "print-elided.hh"
+
+namespace nix {
+
+std::ostream &
+escapeString(std::ostream & str, const std::string_view string, size_t maxLength, bool ansiColors)
+{
+    size_t charsPrinted = 0;
+    if (ansiColors)
+        str << ANSI_MAGENTA;
+    str << "\"";
+    for (auto i = string.begin(); i != string.end(); ++i) {
+        if (charsPrinted >= maxLength) {
+            str << "\" ";
+            printElided(str, string.length() - charsPrinted, "byte", "bytes", ansiColors);
+            return str;
+        }
+        if (*i == '\"' || *i == '\\') str << "\\" << *i;
+        else if (*i == '\n') str << "\\n";
+        else if (*i == '\r') str << "\\r";
+        else if (*i == '\t') str << "\\t";
+        else if (*i == '$' && *(i+1) == '{') str << "\\" << *i;
+        else str << *i;
+        charsPrinted++;
+    }
+    str << "\"";
+    if (ansiColors)
+        str << ANSI_NORMAL;
+    return str;
+}
+
+}; // namespace nix
diff --git a/src/libutil/escape-string.hh b/src/libutil/escape-string.hh
new file mode 100644
index 000000000..28c6c8d64
--- /dev/null
+++ b/src/libutil/escape-string.hh
@@ -0,0 +1,34 @@
+#pragma once
+
+#include <limits>
+#include <ostream>
+
+namespace nix {
+
+/**
+ * Escape a string for output.
+ *
+ * With default optional parameters, the output string will round-trip through
+ * the Nix evaluator (i.e. you can copy/paste this function's output into the
+ * REPL and have it evaluate as the string that got passed in).
+ *
+ * With non-default optional parameters, the output string will be
+ * human-readable.
+ */
+
+std::ostream & escapeString(
+    std::ostream & output,
+    const std::string_view string,
+    size_t maxLength = std::numeric_limits<size_t>::max(),
+    bool ansiColors = false
+);
+
+/**
+ * Escape a string for output, writing the escaped result to a new string.
+ */
+inline std::ostream & escapeString(std::ostream & output, const char * string)
+{
+    return escapeString(output, std::string_view(string));
+}
+
+} // namespace nix
diff --git a/src/libutil/meson.build b/src/libutil/meson.build
index ade925bcf..11bf97ee7 100644
--- a/src/libutil/meson.build
+++ b/src/libutil/meson.build
@@ -9,6 +9,7 @@ libutil_sources = files(
   'english.cc',
   'error.cc',
   'escape-char.cc',
+  'escape-string.cc',
   'exit.cc',
   'experimental-features.cc',
   'filesystem.cc',
@@ -19,6 +20,7 @@ libutil_sources = files(
   'logging.cc',
   'namespaces.cc',
   'position.cc',
+  'print-elided.cc',
   'references.cc',
   'serialise.cc',
   'shlex.cc',
@@ -52,6 +54,7 @@ libutil_headers = files(
   'english.hh',
   'error.hh',
   'escape-char.hh',
+  'escape-string.hh',
   'exit.hh',
   'experimental-features.hh',
   'experimental-features-json.hh',
@@ -70,6 +73,7 @@ libutil_headers = files(
   'namespaces.hh',
   'pool.hh',
   'position.hh',
+  'print-elided.hh',
   'ref.hh',
   'references.hh',
   'regex-combinators.hh',
diff --git a/src/libutil/print-elided.cc b/src/libutil/print-elided.cc
new file mode 100644
index 000000000..75357e5bc
--- /dev/null
+++ b/src/libutil/print-elided.cc
@@ -0,0 +1,23 @@
+#include "print-elided.hh"
+#include "ansicolor.hh"
+#include "english.hh"
+
+namespace nix {
+
+void printElided(
+    std::ostream & output,
+    unsigned int value,
+    const std::string_view single,
+    const std::string_view plural,
+    bool ansiColors)
+{
+    if (ansiColors)
+        output << ANSI_FAINT;
+    output << "«";
+    pluralize(output, value, single, plural);
+    output << " elided»";
+    if (ansiColors)
+        output << ANSI_NORMAL;
+}
+
+}
diff --git a/src/libutil/print-elided.hh b/src/libutil/print-elided.hh
new file mode 100644
index 000000000..a99b15ca1
--- /dev/null
+++ b/src/libutil/print-elided.hh
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <ostream>
+
+
+namespace nix {
+
+/**
+ * Print an `«... elided»` placeholder.
+ *
+ * Arguments are forwarded to `pluralize`.
+ *
+ * If `ansiColors` is set, the output will be wrapped in `ANSI_FAINT`.
+ */
+void printElided(
+    std::ostream & output,
+    unsigned int value,
+    const std::string_view single,
+    const std::string_view plural,
+    bool ansiColors
+);
+
+}