From: Joel Rosdahl <joel@rosdahl.net>
Date: Sun, 2 Jul 2023 08:44:16 +0000 (+0200)
Subject: feat: Support escaping dollar signs in configuration values
X-Git-Tag: v4.9~155
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c92b683b3a2ab1215fb4d9a99e3f42400562d3c2;p=thirdparty%2Fccache.git

feat: Support escaping dollar signs in configuration values
---

diff --git a/doc/MANUAL.adoc b/doc/MANUAL.adoc
index 722c9d9a3..4d3c6686c 100644
--- a/doc/MANUAL.adoc
+++ b/doc/MANUAL.adoc
@@ -371,6 +371,15 @@ See also the <<config_cache_dir,*cache_dir*>> configuration option for how the
 cache directory location is determined.
 
 
+=== Configuration value syntax
+
+All configuration values support expansion of environment variables. The syntax
+is similar to POSIX shell syntax: `$VAR` or `${VAR}`. Both variants will expand
+to the value of the environment variable `VAR`.
+
+Two consecutive dollar signs (`$$`) will expand to a single dollar sign (`$`).
+
+
 === Configuration file syntax
 
 Configuration files are in a simple "`key = value`" format, one option per
@@ -382,7 +391,6 @@ is whitespace surrounding keys and values. Example:
 max_size = 10G
 -------------------------------------------------------------------------------
 
-
 === Boolean values
 
 Some configuration options are boolean values (i.e. truth values). In a
diff --git a/src/Util.cpp b/src/Util.cpp
index 6ba1b3431..e00502fa5 100644
--- a/src/Util.cpp
+++ b/src/Util.cpp
@@ -439,10 +439,18 @@ expand_environment_variables(const std::string& str)
   std::string result;
   const char* left = str.c_str();
   const char* right = left;
+
   while (*right) {
     if (*right == '$') {
       result.append(left, right - left);
 
+      if (*(right + 1) == '$') {
+        result += '$';
+        right += 2;
+        left = right;
+        continue;
+      }
+
       left = right + 1;
       bool curly = *left == '{';
       if (curly) {
@@ -474,6 +482,7 @@ expand_environment_variables(const std::string& str)
     }
     ++right;
   }
+
   result += left;
   return result;
 }
diff --git a/unittest/test_Util.cpp b/unittest/test_Util.cpp
index fd02076b7..ae320edf3 100644
--- a/unittest/test_Util.cpp
+++ b/unittest/test_Util.cpp
@@ -187,7 +187,9 @@ TEST_CASE("Util::expand_environment_variables")
 
   CHECK(Util::expand_environment_variables("") == "");
   CHECK(Util::expand_environment_variables("$FOO") == "bar");
-  CHECK(Util::expand_environment_variables("$") == "$");
+  CHECK(Util::expand_environment_variables("$$FOO") == "$FOO");
+  CHECK(Util::expand_environment_variables("$$$FOO") == "$bar");
+  CHECK(Util::expand_environment_variables("$ $$ $") == "$ $ $");
   CHECK(Util::expand_environment_variables("$FOO $FOO:$FOO") == "bar bar:bar");
   CHECK(Util::expand_environment_variables("x$FOO") == "xbar");
   CHECK(Util::expand_environment_variables("${FOO}x") == "barx");