* Refactor InputStream and affected commands.
First, making `values` private and leaning on the `Stream` implementation makes
consumes of `InputStream` less likely to have to change in the future, if we
change what an `InputStream` is internally.
Second, we're dropping `Option<InputStream>` as the input to pipelines,
internals, and externals. Instead, `InputStream.is_empty` can be used to check
for "emptiness". Empty streams are typically only ever used as the first input
to a pipeline.
* Add run_external internal command.
We want to push external commands closer to internal commands, eventually
eliminating the concept of "external" completely. This means we can consolidate
a couple of things:
- Variable evaluation (for example, `$it`, `$nu`, alias vars)
- Behaviour of whole stream vs per-item external execution
It should also make it easier for us to start introducing argument signatures
for external commands,
* Update run_external.rs
* Update run_external.rs
* Update run_external.rs
* Update run_external.rs
Co-authored-by: Jonathan Turner <jonathandturner@users.noreply.github.com>
* headers plugin
* Remove plugin
* Add non-functioning headers command
* Add ability to extract headers from first row
* Refactor header extraction
* Rebuild indexmap with proper headers
* Rebuild result properly
* Compiling, probably wrapped too much?
* Refactoring
* Deal with case of empty header cell
* Deal with case of empty header cell
* Fix formatting
* Fix linting, attempt 2.
* Move whole_stream_command(Headers) to more appropriate section
* ... more linting
* Return Err(ShellError...) instead of panic, yield each row instead of entire table
* Insert Column[index] if no header info is found.
* Update error description
* Add initial test
* Add tests for headers command
* Lint test cases in headers
* Change ShellError for headers, Add sample_headers file to utils.rs
* Add empty sheet to test file
* Revert "Add empty sheet to test file"
This reverts commit a4bf38a31d.
* Show error message when given empty table
