Add setenv

CHANGELOG.md

@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Functions
   - `longestCommonPrefix`: Longest leading substring shared by every string in a list. `([str] -- str)`
+  - `setenv`: Set an environment variable by name, taking the value then the name.
+    Use when the name is not known statically; otherwise prefer `$NAME!`. `(str str -- )`
   - `stdinIsTerminal`, `stdoutIsTerminal`, and `stderrIsTerminal`: Report whether
     the current effective standard stream is connected to a terminal or Windows
     console. Regular files, pipes, captures, and non-file streams return false.

doc/functions.inc.html

@@ -30,6 +30,7 @@ <h1 id="functions-built-ins">Built-ins <a class="section-link" href="#functions-
         <tr> <td><code>defs</code></td> <td>Print available definitions at the current location.</td> <td><code>(--)</code></td> </tr>
         <tr> <td><code>completionDefs</code></td> <td>Push a dictionary of completion definitions. Keys are command names, values are lists of quotations.</td> <td><code>(-- dict)</code></td> </tr>
         <tr> <td><code>env</code></td> <td>Write all environment variables to stderr in sorted order.</td> <td><code>(--)</code></td> </tr>
+        <tr> <td><code>setenv</code></td> <td>Set an environment variable by name, taking the value then the name. Use when the name is not known statically; otherwise prefer <code>$NAME!</code>.</td> <td><code>(<span class="sig-type sig-type-str">str</span> <span class="sig-type sig-type-str">str</span> -- )</code></td> </tr>
         <tr> <td><code>unsetenv</code></td> <td>Remove an environment variable by name. Unsetting a variable that does not exist is not an error.</td> <td><code>(<span class="sig-type sig-type-str">str</span> -- )</code></td> </tr>
         <tr> <td><code>dup</code></td> <td>Duplicate the top stack item.</td> <td><code>(a -- a a)</code></td> </tr>
         <tr> <td><code>swap</code></td> <td>Swap the top two stack items.</td> <td><code>(a b -- b a)</code></td> </tr>

doc/mshell.md

@@ -327,6 +327,10 @@ An environment variable can be removed with the `unsetenv` built-in,
 which takes the variable name as a string.
 Unsetting a variable that does not exist is not an error.
 
+When the variable name is not known statically,
+an environment variable can be set with the `setenv` built-in,
+which takes the value then the name as strings.
+
 ```mshell
 $HOME cd
 
@@ -338,6 +342,9 @@ $HOME cd
 
 # Removing an environment variable
 "MSHELL_VAR" unsetenv
+
+# Setting with a dynamic name, value then name
+"Hello, World!" "MSHELL_VAR" setenv
 ```
 
 ## Indexing
@@ -1057,6 +1064,7 @@ end wl # Output: 11
 - `defs`: Print available definitions at the current location (--)
 - `env`: Write all environment variables to stderr in sorted order (--)
 - `completionDefs`: Push a dictionary of completion definitions. Keys are command names, values are lists of quotations. `( -- dict)`
+- `setenv`: Set an environment variable by name, value then name. Use when the name is not known statically; otherwise prefer `$NAME!`. `(str str -- )`
 - `unsetenv`: Remove an environment variable by name. Unsetting a variable that does not exist is not an error. `(str -- )`
 - `dup`: Duplicate (a -- a a)
 - `swap`: Swap (a b -- b a)

doc/variables.inc.html

@@ -57,10 +57,12 @@ <h1 id="variables-environment">Environment Variables <a class="section-link" hre
 Environment variables are always exported to subprocesses, so setting them affects subsequent command executions.
 Remove one with the <code>unsetenv</code> built-in, which takes the name as a string.
 Unsetting a variable that does not exist is not an error.
+When the variable name is not known statically, set one with the <code>setenv</code> built-in, which takes the value then the name.
 </p>
 
 <pre>
-<code><span class="mshellSTRING">"LOG_LEVEL"</span> <span class="mshellLITERAL">unsetenv</span></code>
+<code><span class="mshellSTRING">"LOG_LEVEL"</span> <span class="mshellLITERAL">unsetenv</span>
+<span class="mshellSTRING">"info"</span> <span class="mshellSTRING">"LOG_LEVEL"</span> <span class="mshellLITERAL">setenv</span></code>
 </pre>
 
 <pre>

mshell/BuiltInList.go

@@ -162,6 +162,7 @@ var BuiltInList = map[string]struct{}{
 	"set": {},
 	"setAt": {},
 	"setd": {},
+	"setenv": {},
 	"sha256sum": {},
 	"skip": {},
 	"sleep": {},

mshell/Evaluator.go

@@ -7216,6 +7216,36 @@ func (state *EvalState) evaluateToken(t Token, stack *MShellStack, context Execu
 					}
 
 					stack.Push(MShellPath{path})
+				} else if t.Lexeme == "setenv" {
+					obj1, err := stack.Pop()
+					if err != nil {
+						return state.FailWithMessage(fmt.Sprintf("%d:%d: Cannot do 'setenv' operation on an empty stack.\n", t.Line, t.Column))
+					}
+
+					varName, err := obj1.CastString()
+					if err != nil {
+						return state.FailWithMessage(fmt.Sprintf("%d:%d: Cannot use a %s as an environment variable name.\n", t.Line, t.Column, obj1.TypeName()))
+					}
+
+					obj2, err := stack.Pop()
+					if err != nil {
+						return state.FailWithMessage(fmt.Sprintf("%d:%d: Cannot do 'setenv' operation on a stack with less than two items.\n", t.Line, t.Column))
+					}
+
+					varValue, err := obj2.CastString()
+					if err != nil {
+						return state.FailWithMessage(fmt.Sprintf("%d:%d: Cannot use a %s as an environment variable value.\n", t.Line, t.Column, obj2.TypeName()))
+					}
+
+					err = os.Setenv(varName, varValue)
+					if err != nil {
+						return state.FailWithMessage(fmt.Sprintf("%d:%d: Could not set the environment variable '%s' to '%s'.\n", t.Line, t.Column, varName, varValue))
+					}
+
+					// If it was the PATH, refresh all the binaries
+					if varName == "PATH" {
+						context.Pbm.Update()
+					}
 				} else if t.Lexeme == "unsetenv" {
 					obj1, err := stack.Pop()
 					if err != nil {

mshell/TypeBuiltins.go

@@ -449,6 +449,8 @@ func builtinSigsByName(arena *TypeArena, names *NameTable) map[NameId][]QuoteSig
 		r.reg(name, "(str | path -- )")
 	}
 	r.reg("cd", "(str | path -- )")
+	// setenv : set an environment variable, value then name
+	r.reg("setenv", "(str str -- )")
 	// unsetenv : remove an environment variable by name
 	r.reg("unsetenv", "(str -- )")
 	// cdh / cdp : interactive directory history / pop navigation

tests/success/setenv.msh

@@ -0,0 +1,9 @@
+# Set an environment variable with a dynamic name, value then name.
+"hello" "MSH_SETENV_TEST" setenv
+$MSH_SETENV_TEST? str wl
+$MSH_SETENV_TEST wl
+# Overwriting an existing variable.
+"world" "MSH_SETENV_TEST" setenv
+$MSH_SETENV_TEST wl
+"MSH_SETENV_TEST" unsetenv
+$MSH_SETENV_TEST? str wl

tests/success/setenv.msh.stdout

@@ -0,0 +1,4 @@
+true
+hello
+world
+false