vsg 0.2

VHDL Style Guide

Vhdl Style Guide (VSG)
======================

**Coding style enforcement for VHDL.**

After recently performing code reviews, most of the issues found were related to style.
Time spent in code reviews addressing style issues is a waste.
Depending on your process, style issues can take a lot of time to resolve.

1. Create finding/ticket/issue
2. Disposition
3. Fix
4. Verify fix

Spending less time on style issues, leaves more time to analyze the substance of the code.
Ultimately, this will reduce the amount of time performing code reviews.
Spending more time on substance than style will result in higher quality code that ultimately costs less.

## Key benefits

* Define VHDL coding standards
* Makes coding standards visible to everyone
* Improve code reviews
* Quickly bring code up to current standards

VSG allows the style of the code to be defined and enforced over part or the entire code base.
Configurations allow for multiple coding standards.

## Key Features

* Command line tool
- integrate into continuous integration flow
* Fixes and/or reports issues found
- whitespace
- horizontal
- vertical
- upper and lower case
- keyword alignments
- etc...
* Fully configurable rules via JSON configuration file
- Disable rules
- Alter behavior of existing rules
- Change phase of execution
* Localize rule sets
- Create your own rules using python
- Use existing rules as a template
- Fully integrates into base rule set

## Installation

You can get the latest released version of VSG via **pip**.

```
pip install vsg
```

The latest development version can be cloned...

```
git clone https://github.com/jeremiah-c-leary/vhdl-style-guide.git
```
...and then installed locally...
```
python setup.py install
```

## Usage

VSG is a command line tool and is invoked with...
```
$vsg

usage: VHDL Style Guide (VSG) [-h] -f FILENAME [--local_rules LOCAL_RULES]
[--configuration CONFIGURATION] [--fix]

Analyzes VHDL files for style guide violations.

optional arguments:
-h, --help show this help message and exit
-f FILENAME, --filename FILENAME
File to analyze
--local_rules LOCAL_RULES
Path to local rules
--configuration CONFIGURATION
JSON configuration file
--fix Fix issues found
```

Here is an example output running against a test file:
```
$ vsg -f PIC.vhd
File: PIC.vhd
==============
Phase 1... Reporting
Phase 2... Reporting
Phase 3... Reporting
Phase 4... Reporting
Phase 5... Reporting
comment_002 | 51 | Ensure proper alignment of comment with previous line.
comment_002 | 52 | Ensure proper alignment of comment with previous line.
comment_002 | 54 | Ensure proper alignment of comment with previous line.
comment_002 | 55 | Ensure proper alignment of comment with previous line.
comment_003 | 76-256 | Inconsistent alignment of comments within process.
sequential_005 | 87-93 | Inconsistent alignment of "<=" in group of lines.
sequential_005 | 102-103 | Inconsistent alignment of "<=" in group of lines.
sequential_005 | 105-108 | Inconsistent alignment of "<=" in group of lines.
sequential_005 | 110-113 | Inconsistent alignment of "<=" in group of lines.
sequential_005 | 115-118 | Inconsistent alignment of "<=" in group of lines.
sequential_005 | 120-124 | Inconsistent alignment of "<=" in group of lines.
sequential_005 | 129-133 | Inconsistent alignment of "<=" in group of lines.
sequential_005 | 160-161 | Inconsistent alignment of "<=" in group of lines.
sequential_005 | 173-174 | Inconsistent alignment of "<=" in group of lines.
comment_002 | 183 | Ensure proper alignment of comment with previous line.
sequential_005 | 225-226 | Inconsistent alignment of "<=" in group of lines.
sequential_005 | 238-239 | Inconsistent alignment of "<=" in group of lines.
Phase 6... Not executed
Phase 7... Not executed
==============
Total Rules Checked: 204
Total Failures: 523
```

## Configuring

Any attribute of any rule can be configured by using the --configuration option and a JSON file.
This is the basic form of a configuration file:

```json
{
"rule":{
"global":{
"attributeName":"AttributeValue"
},
"ruleId_ruleNumber":{
"attributeName":"AttributeValue"
}
}
}
```

### Example Configuration: Disabling a rule

Below is an example of a JSON file which disables the rule **entity_004**

```json
{
"rule":{
"entity_004":{
"disable":"True"
}
}
}
```

### Example Configuration: Setting the indent increment size

The indent increment size is the number of spaces an indent level takes.
It can be configured on an per rule basis...

```json
{
"rule":{
"entity_004":{
"indentSize":4
}
}
}
```

...or configured for every rule using **global**:


```json
{
"rule":{
"global":{
"indentSize":4
}
}
}
```

The **global** value will be overridden if the same attribute is specified for an individual rule.

## Running Tests

You can run all the tests at the top level by invoking the following command...

```
$ python setup.py test
running test
Searching for nose
.
.
.

----------------------------------------------------------------------
Ran 578 tests in 0.364s

OK
```
...or...
```
$ python -m unittest discover
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
----------------------------------------------------------------------
Ran 578 tests in 0.072s

OK
```


## Local rules

VSG supports customization by allowing localized rules.
This is simply a directory with an __init__.py file and one or more python files.
The files should follow the same structure and naming convention as the rules found in the vsg/rules directory.

The localized rules will be used when the -l command line argument is given.

## Phases

The rules are grouped together and ran in phases.
If issues are found during a phase, then successive phases will not execute.

### Phase 1 - Structural

This phase checks the structure of VHDL statements.
This ensures the VHDL is structured properly for future phases.

### Phase 2 - Whitespace

This phase checks whitespace rules.
However, this does not include indentation.

### Phase 3 - Vertical Spacing

This phase checks all vertical spacing requirements are met.

### Phase 4 - Indentation

This phase checks all indentation rules

### Phase 5 - Alignment

This phase checks all alignment rules

### Phase 6 - Capitalization

This phase checks capitalization rules

### Phase 7 - Naming conventions

This phase checks naming restrictions for signals, constants, ports, etc...