Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/propensive/caesura

Simple parsing of CSV into case classes in Scala
https://github.com/propensive/caesura

csv csv-parser scala tsv tsv-parser

Last synced: 9 days ago
JSON representation

Simple parsing of CSV into case classes in Scala

Awesome Lists containing this project

README 

        
[GitHub Workflow](https://github.com/propensive/caesura/actions)

[](https://discord.com/invite/MBUrkTgMnA)




# Caesura



__Simple parsing of CSV into case classes__



Caesura provides an API for reading and writing CSV and TSV.



## Features



- parse CSV and TSV data

- serialize product-like data (e.g. tuples or case classes) to CSV/TSV rows

- typeclass-based serialization and deserialization

- generic derivation of typeclasses for product and coproduct types



## Availability



## Getting Started



### Reading CSV Data



CSV data can be read from any value whose type has a `Source` typeclass instance in scope, such as `Text` or a `File` from

[Galilei](https://github.com/propensive/galilei), passing it to the `Csv.parse` method. For example,

```scala

import caesura.*

import galilei.*

val file: File = ...

val csv: Csv = Csv.parse(file)

```



Likewise, TSV data can be read with:

```scala

import caesura.*

import galilei.*

val file: File = ...

val tsv: Tsv = Tsv.parse(file)

```



### `Row`, `Csv` and `Tsv` Types



Both `Csv` and `Tsv` values are nothing more than wrappers around a sequence of `Row` instances, which are themselves `IArray`s

of `Text` values. While `Row` instances are the same regardless of whether their purpose is for CSV or TSV data, when wrapped

in a `Csv` or `Tsv` instance, they become serializable with the appropriate column separator (`','` or `'\t'`) and escaping.



Indeed, the companion objects `Csv` and `Tsv` are just two instances of the `RowFormat` type with different `separator` values

and implementations of the `RowFormat#escape` method, and alternative formats may be created by subclassing `RowFormat` and

overriding parameters.



### Interpreting rows



A `Row` instance may be converted to a case class by calling its `Row#as` method with a target type parameter, for example,

```scala

val row: Row = Csv.parseRow(t"Richard,Smith,38")



case class Person(firstName: Text, lastName, Text, age: Int)

val person: Person = row.as[Person]

```

will instantiate an instance of `Person`, `Person("Richard", "Smith", 38)` by associating the positional fields in the case

class definition with those in the `Row`, and applying the appropriate conversions to construct parameters of the appropriate

types to instantiate the `Person`. In this example, the `age` field is parsed to construct an `Int`.



If a case class definition includes a nested case class, for example,

```scala

case class Person(firstName: Text, lastName: Text, age: Int)

case class Role(title: Text, person: Person, managerial: Boolean)

```

then the structure would first be flattened, so the order of the positional fields for the `Role` case class would be,

`title` (0), `person.firstName` (1), `person.lastName` (2), `person.age` (3), and `managerial` (4).



This means the mapping from rows to case class instances is brittle: an additional field in a nested case class would be

certain to break interpretation of rows. But that is unfortunately the nature of working with CSV.



The `as` method also exists on `Csv` and `Tsv`, and will return a `List` of values of the specified type.



### Serializing to rows



`Csv` and `Tsv` instances may also be serialized to streams of data. Any `Seq[T]` (e.g. `List[T]` or `LazyList[T]`) may be

transformed to CSV or TSV by calling the `csv` or `tsv` extension methods on it. For example,

```scala

val persons: List[Person] =

  List(Person(t"Richard", t"Smith", 38), person2, person3)



val personsTsv: Tsv = persons.tsv

```



## Status



Caesura is classified as __fledgling__. For reference, Soundness projects are

categorized into one of the following five stability levels:



- _embryonic_: for experimental or demonstrative purposes only, without any guarantees of longevity

- _fledgling_: of proven utility, seeking contributions, but liable to significant redesigns

- _maturescent_: major design decisions broady settled, seeking probatory adoption and refinement

- _dependable_: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version `1.0.0` or later

- _adamantine_: proven, reliable and production-ready, with no further breaking changes ever anticipated



Projects at any stability level, even _embryonic_ projects, can still be used,

as long as caution is taken to avoid a mismatch between the project's stability

level and the required stability and maintainability of your own project.



Caesura is designed to be _small_. Its entire source code currently consists

of 196 lines of code.



## Building



Caesura will ultimately be built by Fury, when it is published. In the

meantime, two possibilities are offered, however they are acknowledged to be

fragile, inadequately tested, and unsuitable for anything more than

experimentation. They are provided only for the necessity of providing _some_

answer to the question, "how can I try Caesura?".



1. *Copy the sources into your own project*

   

   Read the `fury` file in the repository root to understand Caesura's build

   structure, dependencies and source location; the file format should be short

   and quite intuitive. Copy the sources into a source directory in your own

   project, then repeat (recursively) for each of the dependencies.



   The sources are compiled against the latest nightly release of Scala 3.

   There should be no problem to compile the project together with all of its

   dependencies in a single compilation.



2. *Build with [Wrath](https://github.com/propensive/wrath/)*



   Wrath is a bootstrapping script for building Caesura and other projects in

   the absence of a fully-featured build tool. It is designed to read the `fury`

   file in the project directory, and produce a collection of JAR files which can

   be added to a classpath, by compiling the project and all of its dependencies,

   including the Scala compiler itself.

   

   Download the latest version of

   [`wrath`](https://github.com/propensive/wrath/releases/latest), make it

   executable, and add it to your path, for example by copying it to

   `/usr/local/bin/`.



   Clone this repository inside an empty directory, so that the build can

   safely make clones of repositories it depends on as _peers_ of `caesura`.

   Run `wrath -F` in the repository root. This will download and compile the

   latest version of Scala, as well as all of Caesura's dependencies.



   If the build was successful, the compiled JAR files can be found in the

   `.wrath/dist` directory.



## Contributing



Contributors to Caesura are welcome and encouraged. New contributors may like

to look for issues marked

[beginner](https://github.com/propensive/caesura/labels/beginner).



We suggest that all contributors read the [Contributing

Guide](/contributing.md) to make the process of contributing to Caesura

easier.



Please __do not__ contact project maintainers privately with questions unless

there is a good reason to keep them private. While it can be tempting to

repsond to such questions, private answers cannot be shared with a wider

audience, and it can result in duplication of effort.



## Author



Caesura was designed and developed by Jon Pretty, and commercial support and

training on all aspects of Scala 3 is available from [Propensive

OÜ](https://propensive.com/).



## Name



A _caesura_ is break or pause in a sentence, often indicated by a comma—the same symbol that is used to indicate breaks in a CSV file.



In general, Soundness project names are always chosen with some rationale,

however it is usually frivolous. Each name is chosen for more for its

_uniqueness_ and _intrigue_ than its concision or catchiness, and there is no

bias towards names with positive or "nice" meanings—since many of the libraries

perform some quite unpleasant tasks.



Names should be English words, though many are obscure or archaic, and it

should be noted how willingly English adopts foreign words. Names are generally

of Greek or Latin origin, and have often arrived in English via a romance

language.



## Logo



The logo is a comma, the significant character for separating values in CSV files.



## License



Caesura is copyright © 2024 Jon Pretty & Propensive OÜ, and

is made available under the [Apache 2.0 License](/license.md).