Rust magics have their own regexp

jupytext/magics.py

@@ -15,6 +15,11 @@
         _SCRIPT_EXTENSIONS[ext]['comment'])) for ext in _SCRIPT_EXTENSIONS}
 _LINE_CONTINUATION_RE = re.compile(r'.*\\\s*$')
 
+# Rust magics start with single ':' #351
+_MAGIC_RE['rust'] = re.compile(r"^(// |//)*:[a-zA-Z]")
+_MAGIC_FORCE_ESC_RE['rust'] = re.compile(r"^(// |//)*:[a-zA-Z](.*)//\s*escape")
+_MAGIC_FORCE_ESC_RE['rust'] = re.compile(r"^(// |//)*:[a-zA-Z](.*)//\s*noescape")
+
 # Commands starting with a question or exclamation mark have to be escaped
 _PYTHON_HELP_OR_BASH_CMD = re.compile(r"^(# |#)*(\?|!)\s*[A-Za-z]")
 

tests/notebooks/mirror/ipynb_to_Rmd/evcxr_jupyter_tour.Rmd

@@ -87,7 +87,7 @@ std::thread::spawn({
 We can load external crates. This one takes a while to compile, but once it's compiled, subsequent cells shouldn't need to recompile it, so it should be much quicker.
 
 ```{rust}
-:dep base64 = "0.10.1"
+// :dep base64 = "0.10.1"
 base64::encode(&vec![1, 2, 3, 4])
 ```
 
@@ -169,13 +169,13 @@ s.push_str(format!("foo {}", 42));
 We can print a table of defined variables and their types with the :vars command.
 
 ```{rust}
-:vars
+// :vars
 ```
 
 Other built-in commands can be found via :help
 
 ```{rust}
-:help
+// :help
 ```
 
 ```{rust}

tests/notebooks/mirror/ipynb_to_percent/evcxr_jupyter_tour.rs

@@ -82,7 +82,7 @@ std::thread::spawn({
 // We can load external crates. This one takes a while to compile, but once it's compiled, subsequent cells shouldn't need to recompile it, so it should be much quicker.
 
 // %%
-:dep base64 = "0.10.1"
+// :dep base64 = "0.10.1"
 base64::encode(&vec![1, 2, 3, 4])
 
 // %% [markdown]
@@ -162,12 +162,12 @@ s.push_str(format!("foo {}", 42));
 // We can print a table of defined variables and their types with the :vars command.
 
 // %%
-:vars
+// :vars
 
 // %% [markdown]
 // Other built-in commands can be found via :help
 
 // %%
-:help
+// :help
 
 // %%

tests/notebooks/mirror/ipynb_to_script/evcxr_jupyter_tour.rs

@@ -64,7 +64,7 @@ std::thread::spawn({
 // ## Loading external crates
 // We can load external crates. This one takes a while to compile, but once it's compiled, subsequent cells shouldn't need to recompile it, so it should be much quicker.
 
-:dep base64 = "0.10.1"
+// :dep base64 = "0.10.1"
 base64::encode(&vec![1, 2, 3, 4])
 
 // ## Customizing how types are displayed
@@ -134,10 +134,10 @@ s.push_str(format!("foo {}", 42));
 // ## Seeing what variables have been defined
 // We can print a table of defined variables and their types with the :vars command.
 
-:vars
+// :vars
 
 // Other built-in commands can be found via :help
 
-:help
+// :help
 
 

tests/test_read_simple_rust.py

@@ -0,0 +1,45 @@
+from nbformat.v4.nbbase import new_notebook, new_markdown_cell, new_code_cell
+import jupytext
+from jupytext.compare import compare, compare_notebooks
+
+
+def test_read_magics(text="// :vars\n"):
+    nb = jupytext.reads(text, 'rs')
+    compare_notebooks(nb, new_notebook(cells=[new_code_cell(':vars')]))
+    compare(jupytext.writes(nb, 'rs'), text)
+
+
+def test_read_simple_file(text='''println!("Hello world");
+eprintln!("Hello error");
+format!("Hello {}", "world")
+
+// A Function
+pub fn fib(x: i32) -> i32 {
+    if x <= 2 {0} else {fib(x - 2) + fib(x - 1)}
+}
+
+// This is a
+// Markdown cell
+
+// This is a magic instruction
+// :vars
+
+// This is a rust identifier
+::std::mem::drop
+'''):
+    nb = jupytext.reads(text, 'rs')
+    compare_notebooks(nb, new_notebook(cells=[
+        new_code_cell('''println!("Hello world");
+eprintln!("Hello error");
+format!("Hello {}", "world")'''),
+        new_code_cell('''// A Function
+pub fn fib(x: i32) -> i32 {
+    if x <= 2 {0} else {fib(x - 2) + fib(x - 1)}
+}'''),
+        new_markdown_cell("This is a\nMarkdown cell"),
+        new_code_cell('''// This is a magic instruction
+:vars'''),
+        new_code_cell('''// This is a rust identifier
+::std::mem::drop''')
+    ]))
+    compare(jupytext.writes(nb, 'rs'), text)