source: make sure the block is compiled when parsing (#15798)

# Description
Fixes: https://github.com/nushell/nushell/issues/15749

When sourcing a file, the ir block might be empty because it has been
used before, this pr is going to make sure that the ir block is
compiled.

# User-Facing Changes
```
touch aaa.nu
use aaa.nu
source aaa.nu
```
Will no longer raise an error.

# Tests + Formatting
Added 1 test

# After Submitting
NaN

crates/nu-command/tests/commands/source_env.rs

@@ -1,4 +1,4 @@
-use nu_test_support::fs::Stub::{FileWithContent, FileWithContentToBeTrimmed};
+use nu_test_support::fs::Stub::{EmptyFile, FileWithContent, FileWithContentToBeTrimmed};
 use nu_test_support::nu;
 use nu_test_support::pipeline;
 use nu_test_support::playground::Playground;
@@ -334,3 +334,25 @@ fn source_respects_early_return() {
 
     assert!(actual.err.is_empty());
 }
+
+#[test]
+fn source_after_use_should_not_error() {
+    Playground::setup("source_after_use", |dirs, sandbox| {
+        sandbox.with_files(&[EmptyFile("spam.nu")]);
+
+        let inp = &[r#"use spam.nu"#, r#"source spam.nu"#];
+        let actual = nu!(cwd: dirs.test(), &inp.join("; "));
+        assert!(actual.err.is_empty());
+    })
+}
+
+#[test]
+fn use_after_source_should_not_error() {
+    Playground::setup("use_after_source", |dirs, sandbox| {
+        sandbox.with_files(&[EmptyFile("spam.nu")]);
+
+        let inp = &[r#"source spam.nu"#, r#"use spam.nu"#];
+        let actual = nu!(cwd: dirs.test(), &inp.join("; "));
+        assert!(actual.err.is_empty());
+    })
+}

crates/nu-parser/src/parse_keywords.rs

@@ -1,7 +1,7 @@
 use crate::{
     exportable::Exportable,
     parse_block,
-    parser::{parse_attribute, parse_redirection, redirecting_builtin_error},
+    parser::{compile_block, parse_attribute, parse_redirection, redirecting_builtin_error},
     type_check::{check_block_input_output, type_compatible},
 };
 use itertools::Itertools;
@@ -3805,12 +3805,16 @@ pub fn parse_source(working_set: &mut StateWorkingSet, lite_command: &LiteComman
 
                         // This will load the defs from the file into the
                         // working set, if it was a successful parse.
-                        let block = parse(
+                        let mut block = parse(
                             working_set,
                             Some(&path.path().to_string_lossy()),
                             &contents,
                             scoped,
                         );
+                        if block.ir_block.is_none() {
+                            let block_mut = Arc::make_mut(&mut block);
+                            compile_block(working_set, block_mut);
+                        }
 
                         // Remove the file from the stack of files being processed.
                         working_set.files.pop();

crates/nu-parser/src/parser.rs

@@ -6496,7 +6496,7 @@ pub fn parse_block(
 }
 
 /// Compile an IR block for the `Block`, adding a compile error on failure
-fn compile_block(working_set: &mut StateWorkingSet<'_>, block: &mut Block) {
+pub fn compile_block(working_set: &mut StateWorkingSet<'_>, block: &mut Block) {
     match nu_engine::compile(working_set, block) {
         Ok(ir_block) => {
             block.ir_block = Some(ir_block);