Add -i flag back to get and select (#8488)

https://github.com/nushell/nushell/pull/8379 removed the `-i` flag from
`get` and `select` because the new `?` functionality covers most of the
same use cases. However, https://github.com/nushell/nushell/issues/8480
made me realize that `-i` is still useful when dealing with cell paths
in variables.

This PR re-adds the `-i` flag to `get` and `select`. It works by just
marking every member in the cell path as optional, which will behave
_slightly_ differently than `-i` used to (previously it would suppress
any errors, even type errors) but IMO that's OK.

crates/nu-command/src/filters/get.rs

@@ -41,6 +41,11 @@ If multiple cell paths are given, this will produce a list of values."#
                 "the cell path to the data",
             )
             .rest("rest", SyntaxShape::CellPath, "additional cell paths")
+            .switch(
+                "ignore-errors",
+                "ignore missing data (make all cell path members optional)",
+                Some('i'),
+            )
             .switch(
                 "sensitive",
                 "get path in a case sensitive manner",
@@ -57,12 +62,17 @@ If multiple cell paths are given, this will produce a list of values."#
         input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
         let span = call.head;
-        let cell_path: CellPath = call.req(engine_state, stack, 0)?;
+        let mut cell_path: CellPath = call.req(engine_state, stack, 0)?;
         let rest: Vec<CellPath> = call.rest(engine_state, stack, 1)?;
+        let ignore_errors = call.has_flag("ignore-errors");
         let sensitive = call.has_flag("sensitive");
         let ctrlc = engine_state.ctrlc.clone();
         let metadata = input.metadata();
 
+        if ignore_errors {
+            cell_path.make_optional();
+        }
+
         if rest.is_empty() {
             input
                 .follow_cell_path(&cell_path.members, call.head, !sensitive)

crates/nu-command/src/filters/select.rs

@@ -22,6 +22,11 @@ impl Command for Select {
                 (Type::Record(vec![]), Type::Record(vec![])),
                 (Type::Table(vec![]), Type::Table(vec![])),
             ])
+            .switch(
+                "ignore-errors",
+                "ignore missing data (make all cell path members optional)",
+                Some('i'),
+            )
             .rest(
                 "rest",
                 SyntaxShape::CellPath,
@@ -51,9 +56,16 @@ produce a table, a list will produce a list, and a record will produce a record.
         call: &Call,
         input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        let columns: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
+        let mut columns: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
+        let ignore_errors = call.has_flag("ignore-errors");
         let span = call.head;
 
+        if ignore_errors {
+            for cell_path in &mut columns {
+                cell_path.make_optional();
+            }
+        }
+
         select(engine_state, span, columns, input)
     }
 

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

@@ -241,3 +241,16 @@ fn get_does_not_delve_too_deep_in_nested_lists() {
 
     assert!(actual.err.contains("cannot find column"));
 }
+
+#[test]
+fn ignore_errors_works() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+        let path = "foo";
+        {} | get -i $path | to nuon
+        "#
+    );
+
+    assert_eq!(actual.out, "null");
+}

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

@@ -256,3 +256,16 @@ fn select_failed4() {
 
     assert!(actual.err.contains("Select can't get the same row twice"));
 }
+
+#[test]
+fn ignore_errors_works() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+        let path = "foo";
+        [{}] | select -i $path | to nuon
+        "#
+    );
+
+    assert_eq!(actual.out, "[[foo]; [null]]");
+}