use block signature instead of decl signature for generating help output and when parsing calls

crates/nu-engine/src/documentation.rs

@@ -21,7 +21,9 @@ pub fn get_full_help(
     };
 
     let stack = &mut stack.start_capture();
-    let signature = command.signature().update_from_command(command);
+    let signature = engine_state
+        .get_signature(command)
+        .update_from_command(command);
 
     get_documentation(
         &signature,

crates/nu-parser/src/parser.rs

@@ -954,7 +954,12 @@ pub fn parse_internal_call(
     let _ = working_set.add_span(call.head);
 
     let decl = working_set.get_decl(decl_id);
-    let signature = decl.signature();
+    let signature = if let Some(block_id) = decl.block_id() {
+        let block = working_set.get_block(block_id);
+        *block.signature.clone()
+    } else {
+        decl.signature()
+    };
     let output = signature.get_output_type();
 
     // storing the var ID for later due to borrowing issues

tests/shell/mod.rs

@@ -334,3 +334,69 @@ fn source_empty_file() {
         assert!(actual.out.is_empty());
     })
 }
+
+#[test]
+fn main_script_help_uses_script_name1() {
+    // Note: this test is somewhat fragile and might need to be adapted if the usage help message changes
+    Playground::setup("main_filename", |dirs, sandbox| {
+        sandbox.mkdir("main_filename");
+        sandbox.with_files(&[FileWithContent(
+            "script.nu",
+            r#"def main [] {}
+            "#,
+        )]);
+        let actual = nu!(cwd: dirs.test(), pipeline("nu script.nu --help"));
+        assert!(actual.out.contains("> script.nu"));
+        assert!(!actual.out.contains("> main"));
+    })
+}
+
+#[test]
+fn main_script_help_uses_script_name2() {
+    // Note: this test is somewhat fragile and might need to be adapted if the usage help message changes
+    Playground::setup("main_filename", |dirs, sandbox| {
+        sandbox.mkdir("main_filename");
+        sandbox.with_files(&[FileWithContent(
+            "script.nu",
+            r#"def main [foo: string] {}
+            "#,
+        )]);
+        let actual = nu!(cwd: dirs.test(), pipeline("nu script.nu"));
+        assert!(actual.err.contains("Usage: script.nu"));
+        assert!(!actual.err.contains("Usage: main"));
+    })
+}
+
+#[test]
+fn main_script_subcommand_help_uses_script_name1() {
+    // Note: this test is somewhat fragile and might need to be adapted if the usage help message changes
+    Playground::setup("main_filename", |dirs, sandbox| {
+        sandbox.mkdir("main_filename");
+        sandbox.with_files(&[FileWithContent(
+            "script.nu",
+            r#"def main [] {}
+            def 'main foo' [] {}
+            "#,
+        )]);
+        let actual = nu!(cwd: dirs.test(), pipeline("nu script.nu foo --help"));
+        assert!(actual.out.contains("> script.nu foo"));
+        assert!(!actual.out.contains("> main foo"));
+    })
+}
+
+#[test]
+fn main_script_subcommand_help_uses_script_name2() {
+    // Note: this test is somewhat fragile and might need to be adapted if the usage help message changes
+    Playground::setup("main_filename", |dirs, sandbox| {
+        sandbox.mkdir("main_filename");
+        sandbox.with_files(&[FileWithContent(
+            "script.nu",
+            r#"def main [] {}
+            def 'main foo' [bar: string] {}
+            "#,
+        )]);
+        let actual = nu!(cwd: dirs.test(), pipeline("nu script.nu foo"));
+        assert!(actual.err.contains("Usage: script.nu foo"));
+        assert!(!actual.err.contains("Usage: main foo"));
+    })
+}