Update `setenv()` to take an optional value, also bugfix for `setenv()`

returning a value.

8 files changed, 17 insertions, 12 deletions

diff --git a/CHANGES.md b/CHANGES.md
index f54e4d05..0bbe387f 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -24,6 +24,8 @@
 - Added `at_cleanup()` to register cleanup functions.
 - Added `recursive` argument to `Path.create_directory()` to create parent
   directories if needed.
+- `setenv()` now takes an optional parameter for value, which allows for
+  unsetting environment values.
 - Deprecated:
   - Sets are no longer a separate type with separate methods.
     - Instead of sets, use tables with a value type of `{KeyType:Empty}`.
diff --git a/Makefile b/Makefile
index b8220a95..ab9096cd 100644
--- a/Makefile
+++ b/Makefile
@@ -206,7 +206,6 @@ api-docs: $(API_MD) api/api.md
 
 .PHONY: manpages
 manpages: $(API_YAML) man/man1/tomo.1
-	rm -f man/man3/*
 	./scripts/mandoc_gen.py $(API_YAML)
 
 man/man1/tomo.1: docs/tomo.1.md
diff --git a/api/api.md b/api/api.md
index ec6ffb49..f52691d3 100644
--- a/api/api.md
+++ b/api/api.md
@@ -166,7 +166,7 @@ say("world!")
 ## setenv
 
 ```tomo
-setenv : func(name: Text, value: Text -> Void)
+setenv : func(name: Text, value: Text? -> Void)
 ```
 
 Sets an environment variable.
@@ -174,7 +174,7 @@ Sets an environment variable.
 Argument | Type | Description | Default
 ---------|------|-------------|---------
 name | `Text` | The name of the environment variable to set.  | -
-value | `Text` | The new value of the environment variable.  | -
+value | `Text?` | The new value of the environment variable. If `none`, then the environment variable will be unset.  | -
 
 **Return:** Nothing.
 
diff --git a/api/builtins.md b/api/builtins.md
index 6d042741..2ef14275 100644
--- a/api/builtins.md
+++ b/api/builtins.md
@@ -166,7 +166,7 @@ say("world!")
 ## setenv
 
 ```tomo
-setenv : func(name: Text, value: Text -> Void)
+setenv : func(name: Text, value: Text? -> Void)
 ```
 
 Sets an environment variable.
@@ -174,7 +174,7 @@ Sets an environment variable.
 Argument | Type | Description | Default
 ---------|------|-------------|---------
 name | `Text` | The name of the environment variable to set.  | -
-value | `Text` | The new value of the environment variable.  | -
+value | `Text?` | The new value of the environment variable. If `none`, then the environment variable will be unset.  | -
 
 **Return:** Nothing.
 
diff --git a/api/builtins.yaml b/api/builtins.yaml
index 764a1bd4..af7c9319 100644
--- a/api/builtins.yaml
+++ b/api/builtins.yaml
@@ -157,9 +157,10 @@ setenv:
       description: >
         The name of the environment variable to set.
     value:
-      type: 'Text'
+      type: 'Text?'
       description: >
-        The new value of the environment variable.
+        The new value of the environment variable. If `none`, then the
+        environment variable will be unset.
   example: |
     setenv("FOOBAR", "xyz")
 
diff --git a/man/man3/tomo-setenv.3 b/man/man3/tomo-setenv.3
index a9ed528d..faa6a662 100644
--- a/man/man3/tomo-setenv.3
+++ b/man/man3/tomo-setenv.3
@@ -2,14 +2,14 @@
 .\" Copyright (c) 2025 Bruce Hill
 .\" All rights reserved.
 .\"
-.TH setenv 3 2025-05-17 "Tomo man-pages"
+.TH setenv 3 2025-11-27 "Tomo man-pages"
 .SH NAME
 setenv \- set an environment variable
 .SH LIBRARY
 Tomo Standard Library
 .SH SYNOPSIS
 .nf
-.BI setenv\ :\ func(name:\ Text,\ value:\ Text\ ->\ Void)
+.BI setenv\ :\ func(name:\ Text,\ value:\ Text?\ ->\ Void)
 .fi
 .SH DESCRIPTION
 Sets an environment variable.
@@ -23,7 +23,7 @@ lb lb lbx lb
 l l l l.
 Name	Type	Description	Default
 name	Text	The name of the environment variable to set. 	-
-value	Text	The new value of the environment variable. 	-
+value	Text?	The new value of the environment variable. If `none`, then the environment variable will be unset. 	-
 .TE
 .SH RETURN
 Nothing.
diff --git a/src/environment.c b/src/environment.c
index 88a15bb5..43d22c3d 100644
--- a/src/environment.c
+++ b/src/environment.c
@@ -540,7 +540,7 @@ env_t *global_env(bool source_mapping) {
         {"getenv", "getenv_text", "func(name:Text -> Text?)"},
         {"print", "say", "func(text:Text, newline=yes)"},
         {"say", "say", "func(text:Text, newline=yes)"},
-        {"setenv", "setenv_text", "func(name:Text, value:Text -> Text?)"},
+        {"setenv", "setenv_text", "func(name:Text, value:Text?)"},
         {"sleep", "sleep_num", "func(seconds:Num)"},
     };
 
diff --git a/src/stdlib/stdlib.c b/src/stdlib/stdlib.c
index 21547efe..8ec9e90b 100644
--- a/src/stdlib/stdlib.c
+++ b/src/stdlib/stdlib.c
@@ -219,7 +219,10 @@ OptionalText_t getenv_text(Text_t name) {
 }
 
 public
-void setenv_text(Text_t name, Text_t value) { setenv(Text$as_c_string(name), Text$as_c_string(value), 1); }
+void setenv_text(Text_t name, OptionalText_t value) {
+    if (value.tag == TEXT_NONE) unsetenv(Text$as_c_string(name));
+    else setenv(Text$as_c_string(name), Text$as_c_string(value), 1);
+}
 
 typedef struct cleanup_s {
     Closure_t cleanup_fn;