### Install Solargraph Gem

Source: https://solargraph.org/guides/getting-started

Installs the Solargraph gem via the command line.

```bash
gem install solargraph
```

--------------------------------

### Install Xcode Command Line Tools

Source: https://solargraph.org/guides/troubleshooting

Ensure the necessary development tools are installed to build native extensions on macOS.

```bash
xcode-select --install
sudo xcodebuild -license

```

--------------------------------

### Get Completion Suggestions

Source: https://solargraph.org/guides/code-examples

Retrieve code completion suggestions for a given position in a source file. Requires mapping the source to an ApiMap and using clip_at to get the relevant context.

```ruby
api_map = Solargraph::ApiMap.new
source = Solargraph::Source.load_string("String.", 'example.rb')
api_map.map source
clip = api_map.clip_at('example.rb', Solargraph::Position.new(0, 7))
completion = clip.complete # Suggestions will include String class methods
```

--------------------------------

### Install macOS Ruby Headers

Source: https://solargraph.org/guides/troubleshooting

Manually install Ruby headers required for native extensions on macOS 10.14.

```bash
open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg

```

--------------------------------

### Query Ruby Core Methods with ApiMap

Source: https://solargraph.org/guides/code-examples

Get public instance methods of a Ruby class, such as String. Requires initializing an ApiMap.

```ruby
api_map = Solargraph::ApiMap.new
pins = api_map.get_methods('String') # Get public instance methods of the
                                     # String class
```

--------------------------------

### Method Call Arity Check Example

Source: https://solargraph.org/guides/type-checking

This example demonstrates Solargraph's method call arity check, ensuring that the number of arguments passed to a method matches its defined parameters. An error is reported for too many arguments.

```ruby
# Arity check example
def example(arg1, arg2 = 0); end

example(1)       # OK
example(1, 2)    # OK
example(1, 2, 3) # Error: Too many arguments
```

--------------------------------

### Solargraph Scan Output Example

Source: https://solargraph.org/guides/scanning-workspaces

The verbose output of `solargraph scan -v` lists each code pin analyzed, along with its mapping. A successful scan concludes with a summary of scanned files and pins, and the time taken.

```text
 | 
Solargraph
Solargraph::ApiMap
Solargraph::ApiMap::Cache
Solargraph::ApiMap::Cache.new
Solargraph::ApiMap::Cache#initialize
Solargraph::ApiMap::Cache#initialize | @methods
Solargraph::ApiMap::Cache#initialize | @constants
# (several thousand lines truncated)
Scanned /solargraph (44246 pins) in 35.820807722979225 seconds.
```

--------------------------------

### Overloaded Methods: Tag Inheritance

Source: https://solargraph.org/guides/type-checking

Overloaded methods inherit type tags from superclasses or included modules. This example shows a correct inheritance and an error where the declared return type mismatches the inherited type.

```ruby
module Mixin
  # @return [Integer]
  def integer
    100
  end
end

class User1
  include Mixin

  # OK: User1#integer returns same type as Mixin#integer
  #
  def integer
    200
  end
end

class User2
  include Mixin

  # Error: Declared return type Integer does not match inferred type String
  #
  def integer
    '100'
  end
end
```

--------------------------------

### Strict Level: Parameter Validation

Source: https://solargraph.org/guides/type-checking

If a method includes `@param` tags, the type checker validates the arguments passed during method calls. This example shows a correct call and an incorrect one.

```ruby
class StrictExample
  # @param arg1 [Integer]
  # @return [String]
  def method1(arg1)
    arg1.to_s
  end
end

# OK: Method call has valid argument
StrictExample.new.method1(100)

# Error: arg1 expected Integer, received String
StrictExample.new.method1('100')
```

--------------------------------

### Undefined Types Handling

Source: https://solargraph.org/guides/type-checking

At strict and strong levels, calls to undefined return types result in an 'unresolved call' error, unlike normal checks which ignore them. This example illustrates the error when calling a non-existent method on an inferred nil type.

```ruby
class Example
  def method1; end
end

Example.new.method1.method2
# Normal type checks ignore the call to `method2` because the return type of
# `Example#method1` is untagged.
#
# Strict type checks report an error because `Example#method1` is inferred to
# be `nil` and `NilClass#method2` is not a recognized method.
```

--------------------------------

### Download Core Documentation

Source: https://solargraph.org/guides/getting-started

Downloads documentation for the current Ruby version to enable language server features.

```bash
solargraph download-core
```

--------------------------------

### Verify Ruby and Solargraph Versions

Source: https://solargraph.org/guides/troubleshooting

Check the environment configuration from the command line to ensure the correct versions are being used.

```bash
$ cd /path/to/workspace
$ ruby -v
$ solargraph -v

```

--------------------------------

### Run Solargraph Typechecker from Command Line

Source: https://solargraph.org/guides/type-checking

Execute the Solargraph typechecker from your workspace's root directory. Use this to check all files in the project.

```bash
solargraph typecheck
```

--------------------------------

### Switch Xcode Command Line Tools Path

Source: https://solargraph.org/guides/troubleshooting

Configure the path for Xcode command line tools if native extension builds fail on Xcode 11.

```bash
sudo xcode-select --switch /Library/Developer/CommandLineTools
sudo xcode-select --switch /Applications/Xcode.app

```

--------------------------------

### Query Definitions from Source Location

Source: https://solargraph.org/guides/code-examples

Find definitions of variables or methods at a specific location within a source file after virtualizing it. Requires an ApiMap and a Solargraph::Source object.

```ruby
api_map = Solargraph::ApiMap.new
source = Solargraph::Source.load_string("x = 'string'; puts x", 'example.rb')
api_map.virtualize source
clip = api_map.clip_at('example.rb', Solargraph::Position.new(0, 23))
pins = clip.define # `var` is recognized as a local variable of type String
```

--------------------------------

### Custom Solargraph Methods

Source: https://solargraph.org/guides/language-server

Documentation for custom LSP methods implemented by Solargraph for documentation retrieval and server maintenance.

```APIDOC
## $/solargraph/search

### Description
Search the documentation for class names, methods, etc.

## $/solargraph/document

### Description
Get a page of generated documentation for a class, module, or method.

## $/solargraph/documentGems

### Description
Build YARD documentation for installed gems.

## $/solargraph/downloadCore

### Description
Download the most up-to-date version of the Ruby core documentation.

## $/solargraph/environment

### Description
Get information about the current environment (gem version, config settings, etc.).

## $/solargraph/checkGemVersion

### Description
Check if a newer version of the gem is available.

## $/solargraph/restartServer

### Description
A notification sent from the server to the client requesting that the client shut down and restart the server.
```

--------------------------------

### Custom Solargraph Include Configuration

Source: https://solargraph.org/guides/performance

Customize the .solargraph.yml file to include only specific directories, such as 'lib' and 'app', for faster workspace mapping.

```yaml
include:
- "lib/**/*.rb"
- "app/**/*.rb"

```

--------------------------------

### Documenting return types with @return

Source: https://solargraph.org/guides/yard

Use @return to specify the return type of a method or attribute.

```ruby
class Example
  # @return [String]
  def stringify
    'example'
  end
end

Example.new.stringify # <= Recognized as a String
```

```ruby
class Example
  # @return [Integer]
  attr_reader :number
end
```

--------------------------------

### Load Workspace into ApiMap

Source: https://solargraph.org/guides/code-examples

Load an entire Ruby workspace into an ApiMap for comprehensive analysis. This includes constants defined in the project's code.

```ruby
api_map = Solargraph::ApiMap.load('/path/to/workspace')
pins = api_map.get_constants('') # Results will include constants defined in
                                 # the project's code
```

--------------------------------

### Configure Required Paths

Source: https://solargraph.org/guides/configuration

Add require paths that are not explicitly defined in the project code.

```yaml
require:
- sinatra/base
```

--------------------------------

### Configure Solargraph Plugin in .solargraph.yml

Source: https://solargraph.org/guides/plugins

Registers the plugin gem and enables the custom reporter within the project configuration.

```yaml
plugins:
- solargraph-frozen-string
reporters:
- frozen-string
```

--------------------------------

### Defining method overloads with @overload

Source: https://solargraph.org/guides/yard

Use @overload to document multiple parameter signatures and their corresponding return types.

```ruby
class Example
  # Return one object according to its name or an array of objects from an
  # array of names.
  #
  # @overload find(name)
  #   @param name [String]
  #   @return [Object]
  # @overload find(list)
  #   @param list [Array<String>]
  #   @return [Array<Object>]
  def find(*args); end
end

example = Example.new
example.find('Bob')           # => Object
example.find(['Bob', 'Jane']) # => Array<Object>
```

--------------------------------

### Default Solargraph Configuration

Source: https://solargraph.org/guides/configuration

The default structure of the .solargraph.yml configuration file.

```yaml
include:
- "**/*.rb"
exclude:
- spec/**/*
- test/**/*
- vendor/**/*
- ".bundle/**/*"
require: []
domains: []
reporters:
- rubocop
- require_not_found
max_files: 5000
```

--------------------------------

### Default Solargraph Include Configuration

Source: https://solargraph.org/guides/performance

This is the default configuration for the .solargraph.yml file, which includes all Ruby files in the workspace.

```yaml
include:
- "**/*.rb"

```

--------------------------------

### Configure Diagnostic Reporters

Source: https://solargraph.org/guides/configuration

Specify which diagnostic reporters the language server should use.

```yaml
reporters:
- rubocop
- require_not_found
```

--------------------------------

### Documenting parameters with @param

Source: https://solargraph.org/guides/yard

Use @param to define the expected type of a method argument for type checking.

```ruby
class Example
  # @param int [Integer]
  def take_a_number(int)
    int # <= Recognized as an Integer
  end
end

Example.new.take_a_number(100) # Passes strict type checks

Example.new.take_a_number('A') # Fails strict type checks
```

--------------------------------

### Run Solargraph Typechecker on a Specific File

Source: https://solargraph.org/guides/type-checking

Check for type problems in a particular Ruby file by providing its path to the Solargraph typechecker command.

```bash
solargraph ./path/to/file.rb
```

--------------------------------

### Documenting yielded parameters with @yieldparam

Source: https://solargraph.org/guides/yard

Use @yieldparam to specify the types of parameters passed into a block.

```ruby
class Example
  # @yieldparam [String]
  def change
    yield 'example'
  end
end

Example.new.change do |str|
  str # <= Recognized as a String
end
```

--------------------------------

### Defining methods with @!method

Source: https://solargraph.org/guides/yard

Use the @!method directive to manually add methods to the Solargraph code map.

```ruby
class Example
  # @return [String]
  def foo; end

  # @!method bar()
  #   @return [String]
end

Example.new. # `foo` and `bar` are recognized as available methods
```

--------------------------------

### Register Custom Language Server Message

Source: https://solargraph.org/guides/code-examples

Extend the Solargraph language server by registering a custom message handler. The handler must inherit from Solargraph::LanguageServer::Message::Base and implement a `process` method.

```ruby
class MyMessage < Solargraph::LanguageServer::Message::Base
  def process
    STDERR.puts "Server received MyMessage parameters: #{params}"
  end
end

Solargraph::LanguageServer::Message.register '$/myMessage', MyMessage
```

--------------------------------

### Add File Source to ApiMap

Source: https://solargraph.org/guides/code-examples

Add a Ruby source file to an ApiMap for analysis. This allows querying constants defined within the added source.

```ruby
api_map = Solargraph::ApiMap.new
source = Solargraph::Source.load_string('class MyClass; end', 'my_class.rb')
api_map.map source # Add the source to the map
pins = api_map.get_constants('') # The constants in the global namespace will
                                 # include `MyClass`
```

--------------------------------

### Scan Workspace with Solargraph

Source: https://solargraph.org/guides/scanning-workspaces

Navigate to your workspace and run the `solargraph scan -v` command to perform a verbose scan. This command checks for code that Solargraph cannot parse or map, outputting details for each analyzed code pin.

```bash
cd /path/to/workspace
solargraph scan -v
```

--------------------------------

### Overriding documentation with @!override

Source: https://solargraph.org/guides/yard

Use @!override to add or modify documentation for methods defined in external libraries.

```ruby
# Specify the return type of the Ruby stdlib's Benchmark.measure method
# @!override Benchmark.measure
#   @return [Benchmark::Tms]

result = Benchmark.measure { puts 'test' }
result # => Benchmark::Tms
```

--------------------------------

### Parsing code with @!parse

Source: https://solargraph.org/guides/yard

Use @!parse to force Solargraph to map arbitrary code blocks as if they were part of the runtime.

```ruby
module ClassMethods
  def other_method; end
end

class Example
  # @!parse
  #   extend ClassMethods
end

Example. # `other_method` is recognized as an available method
```

--------------------------------

### Configure Solargraph Typecheck Reporter

Source: https://solargraph.org/guides/type-checking

Add 'typecheck' to your workspace's reporters in `.solargraph.yml` to enable editor diagnostics. You can also specify a check level like 'strict'.

```yaml
reporters:
- typecheck
```

```yaml
reporters:
- typecheck:strict
```

--------------------------------

### Implement a Frozen String Literal Diagnostics Reporter

Source: https://solargraph.org/guides/plugins

Defines a custom diagnostic reporter that warns if a file lacks the frozen_string_literal comment. Requires the solargraph gem.

```ruby
# solargraph-frozen-string.rb

require 'solargraph'

class FrozenStringReporter < Solargraph::Diagnostics::Base
  def diagnose source, _api_map
    return [] if source.code.empty? || source.code.start_with?('# frozen_string_literal:')
    [
        {
            range: Solargraph::Range.from_to(0, 0, 0, source.code.lines[0].length).to_hash,
            severity: Solargraph::Diagnostics::Severities::WARNING,
            source: 'FrozenString',
            message: 'File does not start with frozen_string_literal.'
        }
    ]
  end
end

Solargraph::Diagnostics.register 'frozen-string', FrozenStringReporter
```

--------------------------------

### Strong Level: Parameter and Return Type Requirements

Source: https://solargraph.org/guides/type-checking

Strong checks mandate that all method parameters and return types must be explicitly tagged. Inferred types must also match these tags. Untagged parameters will cause an error.

```ruby
class StrongExample
  # OK: Parameter and return types are valid.
  #
  # @param arg1 [Integer]
  # @return [String]
  def method1(arg1)
    arg1.to_s
  end

  # Error: Parameter type is untagged.
  #
  # @return [String]
  def method2(arg1)
    "received #{arg1}"
  end
end

# OK: Method call is correct
StrongExample.new.method1(100)

# Error: arg1 expected Integer, received String
StrongExample.new.method1('100')
```

--------------------------------

### Strict Level: Attribute Type Tagging

Source: https://solargraph.org/guides/type-checking

Attributes require `@return` tags because their types cannot be inferred from code. Untagged attributes will result in an error.

```ruby
class StrictExample
  # OK: Attribute has a `@return` tag
  #
  # @return [String]
  attr_reader :attr1

  # Error: Untagged attribute cannot be inferred
  #
  attr_reader :attr2
end
```

--------------------------------

### Register Custom Diagnostics Reporter

Source: https://solargraph.org/guides/code-examples

Add a custom diagnostics reporter to Solargraph. The reporter must inherit from Solargraph::Diagnostics::Base and implement a `diagnose` method that returns LSP-compliant diagnostic objects.

```ruby
class MyReporter < Solargraph::Diagnostics::Base
  def diagnose source, api_map
    # Return an array of hash objects that conform to the LSP's Diagnostic
    # specification
    []
  end
end

Solargraph::Diagnostics.register 'my_reporter', MyReporter
```

--------------------------------

### Infer Type from Static Analysis

Source: https://solargraph.org/guides/type-detection

When no type tags are present, Solargraph attempts to infer types by analyzing the code's static structure. This is demonstrated by inferring the return type of `my_string`.

```ruby
class MyClass
  def my_string
    'my_string'
  end
end

MyClass.new.my_string # <= Inferred to be a String
```

--------------------------------

### Defining attributes with @!attribute

Source: https://solargraph.org/guides/yard

Use the @!attribute directive to manually add attributes to the Solargraph code map.

```ruby
class Example
  # @return [String]
  attr_accessor :foo

# @!attribute [rw] bar
  #   @return [String]
end

Example.new. # `foo` and `bar` are recognized as available attributes
```

--------------------------------

### Define Abstract Methods with NotImplementedError

Source: https://solargraph.org/guides/type-checking

A base class defines an interface method that raises NotImplementedError, which subclasses are expected to override.

```ruby
class Greeter
  # Subclasses should implement this method
  #
  # @return [String]
  def greeting
    raise NotImplementedError
  end

  # @return [void]
  def say_greeting
    puts greeting
  end
end

class Person < Greeter
  def greeting
    "Hello!"
  end
end

class Cowboy < Greeter
  def greeting
    "Howdy!"
  end
end

class Stranger < Greeter
end

Person.new.say_greeting    #=> "Hello!"
Cowboy.new.say_greeting    #=> "Howdy!"
Stranger.new.say_greeting  #=> NotImplementedError
```

--------------------------------

### Define Return Type with @return Tag

Source: https://solargraph.org/guides/type-detection

Use the `@return` YARD tag to specify the return type of a method or attribute. This is useful for explicit type definition.

```ruby
class MyClass
  # @return [String]
  attr_accessor :my_string

  # @return [Integer]
  def my_integer
  end
end
```

--------------------------------

### Ignore Typechecker Errors with @sg-ignore

Source: https://solargraph.org/guides/type-checking

Use the `@sg-ignore` directive to tell the typechecker to ignore specific errors, such as unrecognized constants or type inference discrepancies in method tags.

```ruby
# @sg-ignore
UnknownConstant1 # not reported
UnknownConstant2 # reported
```

```ruby
# Ignore the discrepancy between tagged type `String` and inferred type `Integer`
# @sg-ignore
# @return [String]
def foo
  100
end
```

--------------------------------

### Setting block context with @yieldreceiver

Source: https://solargraph.org/guides/yard

Use @yieldreceiver to indicate that the block's self context should be treated as a specific type.

```ruby
module Example
  # @yieldreceiver [String]
  def self.inside_string; end
end

Example.inside_string do
  # Solargraph knows that this block's `self` is a String, so String instance
  # methods like `upcase` are available here.
end
```

--------------------------------

### Use @abstract Tag for Type Checking

Source: https://solargraph.org/guides/type-checking

The @abstract tag informs Solargraph that the return type defined in the base class should be enforced on subclasses.

```ruby
class Greeter
  # @abstract
  # @return [String]
  def greeting
    raise NotImplementedError
  end
end

class Right < Greeter
  # OK: The implementation satisfies the abstract method's expectations
  #
  def greeting
    "hello"
  end
end

class Wrong < Greeter
  # Error: Declared return type String does not match inferred type Integer
  #
  def greeting
    100
  end
end
```

--------------------------------

### Define Parameter Type with @param Tag

Source: https://solargraph.org/guides/type-detection

Use the `@param` YARD tag to define the type of a method parameter. Ensure the tag matches the parameter name.

```ruby
class MyClass
  # @param num [Integer]
  def my_method(num)
  end
end
```

--------------------------------

### Inherit Type from Super Method

Source: https://solargraph.org/guides/type-detection

Solargraph checks super methods for type tags if a method does not have its own. This allows for type definitions to be inherited.

```ruby
module MyModule
  # @return [String]
  def my_string
  end
end

class MyClass
  include MyModule
  def my_string # <= Inherits String return type from MyModule
  end
end
```

--------------------------------

### Define Variable Type with @type Tag

Source: https://solargraph.org/guides/type-detection

Use the `@type` YARD tag to specify the type of a variable. This helps Solargraph understand variable types when they are not immediately obvious.

```ruby
# @type [String]
my_string = get_a_string
```

--------------------------------

### Strict Level: Method Type Inference

Source: https://solargraph.org/guides/type-checking

In the strict level, methods must have a tagged type or an inferred type. Untagged methods with uninferrable types will cause a warning. `@param` tags are optional but checked if present.

```ruby
class StrictExample
  # OK: Type checker knows this method returns a String
  #
  def method1
    'a string'
  end

  # OK: Tagged type matches inferred type
  #
  # @return [String]
  def method2 
    'a string'
  end

  # Error: Method's type could not be inferred
  #
  def method3
    unknown_method
  end
end
```

--------------------------------

### Solargraph Typed Level Type Checking

Source: https://solargraph.org/guides/type-checking

The Typed check level compares YARD type tags with inferred types. It validates `@return`, `@type`, and `@param` tags against inferred types and arguments, while still ignoring undefined types. Loose `@return` tag matches are accepted.

```ruby
class TypedExample
  # OK: Return type matches inferred type
  #
  # @return [String]
  def method1
    'a string'
  end

  # Error: Tagged type Integer does not match inferred type String
  #
  # @return [Integer] 
  def method2
    'a string'
  end

  # OK: Method without `@return` tag is ignored
  #
  def method3
    'a string'
  end

  # OK: Tagged type is valid when inferred type is unknown
  #
  # @return [String]
  def method4
    unknown_method
  end
end
```

--------------------------------

### Specifying variable types with @type

Source: https://solargraph.org/guides/yard

Use @type to explicitly define the type of a variable for better inference.

```ruby
# @type [String]
str = method_returning_string
str # => String
```

--------------------------------

### Solargraph Normal Level Type Checking

Source: https://solargraph.org/guides/type-checking

The Normal check level validates YARD type tags and the arity of calls to explicit methods, but ignores untagged types and undefined types. It resolves namespaces in all type tags.

```ruby
class NormalExample
  # OK: Return type is a recognized class
  #
  # @return [String]
  def method1; end

  # Error: NotARealClass could not be resolved
  #
  # @return [NotARealClass]
  def method2; end

  # OK: Method without `@return` tag is ignored
  def method3; end
end
```

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