Standardise the use of ShellError::UnsupportedInput and ShellError::TypeMismatch and add spans to every instance of the former (#7217)

# Description

* I was dismayed to discover recently that UnsupportedInput and
TypeMismatch are used *extremely* inconsistently across the codebase.
UnsupportedInput is sometimes used for input type-checks (as per the
name!!), but *also* used for argument type-checks. TypeMismatch is also
used for both.
I thus devised the following standard: input type-checking *only* uses
UnsupportedInput, and argument type-checking *only* uses TypeMismatch.
Moreover, to differentiate them, UnsupportedInput now has *two* error
arrows (spans), one pointing at the command and the other at the input
origin, while TypeMismatch only has the one (because the command should
always be nearby)
* In order to apply that standard, a very large number of
UnsupportedInput uses were changed so that the input's span could be
retrieved and delivered to it.
* Additionally, I noticed many places where **errors are not propagated
correctly**: there are lots of `match` sites which take a Value::Error,
then throw it away and replace it with a new Value::Error with
less/misleading information (such as reporting the error as an
"incorrect type"). I believe that the earliest errors are the most
important, and should always be propagated where possible.
* Also, to standardise one broad subset of UnsupportedInput error
messages, who all used slightly different wordings of "expected
`<type>`, got `<type>`", I created OnlySupportsThisInputType as a
variant of it.
* Finally, a bunch of error sites that had "repeated spans" - i.e. where
an error expected two spans, but `call.head` was given for both - were
fixed to use different spans.

# Example
BEFORE
```
〉20b | str starts-with 'a'
Error: nu:🐚:unsupported_input (link)

  × Unsupported input
   ╭─[entry #31:1:1]
 1 │ 20b | str starts-with 'a'
   ·   ┬
   ·   ╰── Input's type is filesize. This command only works with strings.
   ╰────

〉'a' | math cos
Error: nu:🐚:unsupported_input (link)

  × Unsupported input
   ╭─[entry #33:1:1]
 1 │ 'a' | math cos
   · ─┬─
   ·  ╰── Only numerical values are supported, input type: String
   ╰────

〉0x[12] | encode utf8
Error: nu:🐚:unsupported_input (link)

  × Unsupported input
   ╭─[entry #38:1:1]
 1 │ 0x[12] | encode utf8
   ·          ───┬──
   ·             ╰── non-string input
   ╰────
```
AFTER
```
〉20b | str starts-with 'a'
Error: nu:🐚:pipeline_mismatch (link)

  × Pipeline mismatch.
   ╭─[entry #1:1:1]
 1 │ 20b | str starts-with 'a'
   ·   ┬   ───────┬───────
   ·   │          ╰── only string input data is supported
   ·   ╰── input type: filesize
   ╰────

〉'a' | math cos
Error: nu:🐚:pipeline_mismatch (link)

  × Pipeline mismatch.
   ╭─[entry #2:1:1]
 1 │ 'a' | math cos
   · ─┬─   ────┬───
   ·  │        ╰── only numeric input data is supported
   ·  ╰── input type: string
   ╰────

〉0x[12] | encode utf8
Error: nu:🐚:pipeline_mismatch (link)

  × Pipeline mismatch.
   ╭─[entry #3:1:1]
 1 │ 0x[12] | encode utf8
   · ───┬──   ───┬──
   ·    │        ╰── only string input data is supported
   ·    ╰── input type: binary
   ╰────
```

# User-Facing Changes

Various error messages suddenly make more sense (i.e. have two arrows
instead of one).

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-command/src/date/format.rs

@@ -61,13 +61,10 @@ impl Command for SubCommand {
 
         let format = call.opt::<Spanned<String>>(engine_state, stack, 0)?;
 
-        if input.is_nothing() {
-            return Err(ShellError::UnsupportedInput(
-                "Input was nothing. You must pipe an input to this command.".into(),
-                head,
-            ));
+        // This doesn't match explicit nulls
+        if matches!(input, PipelineData::Empty) {
+            return Err(ShellError::PipelineEmpty(head));
         }
-
         input.map(
             move |value| match &format {
                 Some(format) => format_helper(value, format.item.as_str(), format.span, head),
@@ -135,7 +132,7 @@ where
             span,
         },
         Err(_) => Value::Error {
-            error: ShellError::UnsupportedInput("invalid format".to_string(), span),
+            error: ShellError::TypeMismatch("invalid format".to_string(), span),
         },
     }
 }

crates/nu-command/src/date/humanize.rs

@@ -47,6 +47,10 @@ impl Command for SubCommand {
         input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
         let head = call.head;
+        // This doesn't match explicit nulls
+        if matches!(input, PipelineData::Empty) {
+            return Err(ShellError::PipelineEmpty(head));
+        }
         input.map(move |value| helper(value, head), engine_state.ctrlc.clone())
     }
 

crates/nu-command/src/date/to_record.rs

@@ -4,7 +4,8 @@ use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Type;
 use nu_protocol::{
-    Category, Example, PipelineData, ShellError::DatetimeParseError, Signature, Span, Value,
+    Category, Example, PipelineData, ShellError::DatetimeParseError, ShellError::PipelineEmpty,
+    Signature, Span, Value,
 };
 
 #[derive(Clone)]
@@ -41,6 +42,10 @@ impl Command for SubCommand {
         input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
         let head = call.head;
+        // This doesn't match explicit nulls
+        if matches!(input, PipelineData::Empty) {
+            return Err(PipelineEmpty(head));
+        }
         input.map(move |value| helper(value, head), engine_state.ctrlc.clone())
     }
 

crates/nu-command/src/date/to_table.rs

@@ -4,7 +4,8 @@ use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Type;
 use nu_protocol::{
-    Category, Example, PipelineData, ShellError::DatetimeParseError, Signature, Span, Value,
+    Category, Example, PipelineData, ShellError::DatetimeParseError, ShellError::PipelineEmpty,
+    Signature, Span, Value,
 };
 
 #[derive(Clone)]
@@ -41,6 +42,10 @@ impl Command for SubCommand {
         input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
         let head = call.head;
+        // This doesn't match explicit nulls
+        if matches!(input, PipelineData::Empty) {
+            return Err(PipelineEmpty(head));
+        }
         input.map(move |value| helper(value, head), engine_state.ctrlc.clone())
     }
 

crates/nu-command/src/date/to_timezone.rs

@@ -56,7 +56,10 @@ impl Command for SubCommand {
         let head = call.head;
         let timezone: Spanned<String> = call.req(engine_state, stack, 0)?;
 
-        //Ok(PipelineData::new())
+        // This doesn't match explicit nulls
+        if matches!(input, PipelineData::Empty) {
+            return Err(ShellError::PipelineEmpty(head));
+        }
         input.map(
             move |value| helper(value, head, &timezone),
             engine_state.ctrlc.clone(),
@@ -64,26 +67,15 @@ impl Command for SubCommand {
     }
 
     fn examples(&self) -> Vec<Example> {
-        let example_result_1 = || {
-            let dt = match FixedOffset::east_opt(5 * 3600) {
-                Some(dt) => match dt.with_ymd_and_hms(2020, 10, 10, 13, 00, 00) {
-                    LocalResult::Single(dt) => Some(dt),
-                    _ => None,
-                },
-                _ => None,
-            };
-            match dt {
-                Some(dt) => Some(Value::Date {
-                    val: dt,
-                    span: Span::test_data(),
-                }),
-                None => Some(Value::Error {
-                    error: ShellError::UnsupportedInput(
-                        "The given datetime representation is unsupported.".to_string(),
-                        Span::test_data(),
-                    ),
-                }),
-            }
+        let example_result_1 = || match FixedOffset::east_opt(5 * 3600)
+            .expect("to timezone: help example is invalid")
+            .with_ymd_and_hms(2020, 10, 10, 13, 00, 00)
+        {
+            LocalResult::Single(dt) => Some(Value::Date {
+                val: dt,
+                span: Span::test_data(),
+            }),
+            _ => panic!("to timezone: help example is invalid"),
         };
 
         vec![
@@ -145,7 +137,7 @@ fn _to_timezone(dt: DateTime<FixedOffset>, timezone: &Spanned<String>, span: Spa
     match datetime_in_timezone(&dt, timezone.item.as_str()) {
         Ok(dt) => Value::Date { val: dt, span },
         Err(_) => Value::Error {
-            error: ShellError::UnsupportedInput(String::from("invalid time zone"), timezone.span),
+            error: ShellError::TypeMismatch(String::from("invalid time zone"), timezone.span),
         },
     }
 }