Add support for $envvar() function

3 files changed, 96 insertions, 3 deletions

diff --git a/build2/functions-builtin.cxx b/build2/functions-builtin.cxx
index 81a190b..f9bbda5 100644
--- a/build2/functions-builtin.cxx
+++ b/build2/functions-builtin.cxx
@@ -2,6 +2,8 @@
 // copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
 // license   : MIT; see accompanying LICENSE file
 
+#include <cstdlib> // getenv()
+
 #include <build2/function.hxx>
 #include <build2/variable.hxx>
 
@@ -9,6 +11,15 @@ using namespace std;
 
 namespace build2
 {
+  // Return NULL value if an environment variable is not set.
+  //
+  static inline value
+  getenv (const string& name)
+  {
+    const char* v (::getenv (name.c_str ()));
+    return v != nullptr ? value (v) : value ();
+  }
+
   void
   builtin_functions ()
   {
@@ -26,5 +37,26 @@ namespace build2
     f["string"] = [](bool b) {return b ? "true" : "false";};
     f["string"] = [](uint64_t i) {return to_string (i);};
     f["string"] = [](name n) {return to_string (n);};
+
+    // getenv
+    //
+    f["getenv"] = [](string name)
+    {
+      return getenv (name);
+    };
+
+    f["getenv"] = [](names name)
+    {
+      // Note that if the name size is greater than one, we will fail with the
+      // proper diagnostics.
+      //
+      assert (!name.empty ());
+
+      string n (name.size () == 1
+                ? convert<string> (move (name[0]))
+                : convert<string> (move (name)));
+
+      return getenv (n);
+    };
   }
 }
diff --git a/build2/functions-process-path.cxx b/build2/functions-process-path.cxx
index 1b7459b..bbfc427 100644
--- a/build2/functions-process-path.cxx
+++ b/build2/functions-process-path.cxx
@@ -18,8 +18,8 @@ namespace build2
     //
     f["recall"] = &process_path::recall;
     f["effect"] = [](process_path p)
-      {
-        return move (p.effect.empty () ? p.recall : p.effect);
-      };
+    {
+      return move (p.effect.empty () ? p.recall : p.effect);
+    };
   }
 }
diff --git a/tests/function/builtin/testscript b/tests/function/builtin/testscript
index 0b005f3..3e27958 100644
--- a/tests/function/builtin/testscript
+++ b/tests/function/builtin/testscript
@@ -60,3 +60,64 @@
   $* <'print       $identity(abc)'             >'abc';
   $* <'print $type($identity(abc))'            >''         : untyped
 }
+
+: getenv
+:
+{
+  : set
+  :
+  : Here we rely on the facts that on POSIX PATH environment variable most
+  : likely is set at the time of login, and on Windows it is set by build2 on
+  : startup.
+  :
+  : @@ Use a custom variable, when an ability to set environment variables in
+  :    testscript is implemented.
+  :
+  {
+    : string
+    :
+    $* <'print $getenv([string] "PATH")' | set v;
+    ($v != '[null]') || exit "PATH environment variable is not set"
+
+    : untyped
+    :
+    $* <'print $getenv("PATH")' | set v;
+    ($v != '[null]') || exit "PATH environment variable is not set"
+
+    : path
+    :
+    $* <'print $getenv([path] a)' 2>>~/EOE/ != 0
+    <stdin>:1:8: error: unmatched call to getenv(path)
+    /((
+      info: candidate: getenv(<untyped>), qualified name builtin.getenv
+      info: candidate: getenv(string), qualified name builtin.getenv
+    /)|(
+      info: candidate: getenv(string), qualified name builtin.getenv
+      info: candidate: getenv(<untyped>), qualified name builtin.getenv
+    /))
+    EOE
+
+    : none
+    :
+    $* <'print $getenv()' 2>>~/EOE/ != 0
+    <stdin>:1:8: error: unmatched call to getenv()
+    /((
+      info: candidate: getenv(<untyped>), qualified name builtin.getenv
+      info: candidate: getenv(string), qualified name builtin.getenv
+    /)|(
+      info: candidate: getenv(string), qualified name builtin.getenv
+      info: candidate: getenv(<untyped>), qualified name builtin.getenv
+    /))
+    EOE
+
+    : names
+    :
+    $* <'print $getenv(a b)' 2>>EOE != 0
+    error: invalid argument: invalid string value: multiple names
+    EOE
+  }
+
+  : unset
+  :
+  $* <'print $getenv("non-existent-var-name")' >'[null]'
+}