# Stratego API¶

The Statix solver can be called from a Stratego Transformation using the API in the Statix Runtime project. After analysis is executed, the analysis result can be queried using other strategies. In this section, we provide an overview of the availble strategies.

The public API of the Statix runtime is available here. This API strongly depends on the Spoofax constraint analysis library, which is available in the Spoofax Meta Library.

## Single-File Analysis¶

stx-editor-analyze(pre, post|spec-name, init-constraint)


Type: AnalysisAction -> AnalysisResult.

Applies single-file analysis with the specification provided in the arguments. Since this strategy only performs single-file analysis, the current term should always have AnalyzeSingle as top-level constructor. The term and strategy arguments are explained in the following table:

Argument Type Default Description
pre AST -> AST id Transformation to apply before analyzing. This transformation receives the 'parsed AST'.
post AST -> AST id Transformation to apply before analyzing. This transformation receives the result of applying pre to the 'parsed AST', and yields the 'analyzed AST'.
spec-name String The full path to the root module of the specification.
file-constraint String The name of the constraint that should be applied to the pre-transformed AST of each file in the project. This may be a fully qualified name in the form $Module!$ConstraintName, or just a $ConstraintName. In the latter case, the name will be qualified with the spec-name argument. This constraint should have the (Statix) type : scope * Start ## Concurrent Analysis¶ stx-editor-analyze(pre, group, post|spec-name, project-constraint, group-constraint, file-constraint)  Type: AnalysisAction -> AnalysisResult. Applies concurrent multi-file analysis with the specification provided in the arguments. Since this strategy only performs multi-file analysis, the current term should always have AnalyzeMulti as top-level constructor. This strategy chooses the solver based on the metaborg.yaml configuration of the project and the language, but fails with a fatal error if the concurrent solver is not enabled on this project. The term and strategy arguments are explained in the following table: Argument Type Description pre AST -> AST Transformation to apply before analyzing. This transformation receives the 'parsed AST'. group (Resource * AST) -> List(String) Strategy that decides in which group a resource is analyzed. Should return a list with the identifiers of the groups in which the resource should be analyzed. post AST -> AST Transformation to apply before analyzing. This transformation receives the result of applying pre to the 'parsed AST', and yields the 'analyzed AST'. spec-name String The full path to the root module of the specification. project-constraint String The name of the constraint that should be applied to the global scope once. This may be a fully qualified name in the form $Module!$ConstraintName, or just a $ConstraintName. In the latter case, the name will be qualified with the spec-name argument. This constraint should have the (Statix) type : scope
group-constraint String The name of the constraint that should be applied to the each group. This may be a fully qualified name in the form $Module!$ConstraintName, or just a $ConstraintName. In the latter case, the name will be qualified with the spec-name argument. This constraint should have the (Statix) type : scope * string * scope file-constraint String The name of the constraint that should be applied to the pre-transformed AST of each file in the project. This may be a fully qualified name in the form $Module!$ConstraintName, or just a $ConstraintName. In the latter case, the name will be qualified with the spec-name argument. This constraint should have the (Statix) type : scope * Start

## Constraint Evaluation¶

stx-evaluate(|spec-name, constraint)


Type: List(Term) -> Term

Evaluates a functional constraint. The terms in the current term are passed as argument to the constraint, and the result term is the output term of the constraint.

Argument Type Description
spec-name String The full path to the root module of the specification.
constraint String The name of the constraint that should be applied to the term arguments.

The Statix API provides several strategies to query properties from the analysis. These strategies are dicussed in the following sections.

First of all, the analysis result can be obtained by the following strategy:

stx-get-ast-analysis


Type: Term -> Analysis

The stx-get-ast-analysis returns the Analysis object for an AST. This object can later be used to query the scope graph and AST properties set by the Statix specification.

Note that the passed AST should be an analyzed AST. For Spoofax 2 use cases, this means that this strategy can only be used in builders without the (source) annotation.

The returned values will be interpreted relative to the unifier of the analysis. That is, it will be instantiated as much as possible. When a property value contains free variables, those will occur in the property as nabl2.Var: String * String -> Term terms.

## Properties¶

AST properties can be extracted from the analysis result using the following strategy:

stx-get-ast-property(|a, name)


Type: Term -> Term or list(Term).

Argument Type Description
a Analysis Analysis object for the given AST node.
name String The name of the property that is queried.

Given an AST node, this strategy will return the property value. For singleton properties (:= operator), the property value is returned. For bag properties (+= operator), a list with all assigned values is returned. It fails if no property with the given name is set. Therefore, for bag properties the resulting list will never be empty.

Example 1. Consider a Statix specification that contains a @t.prop := val constraint. Using <stx-get-ast-property(|a, "prop")> t will then return val

Example 2. Consider a Statix specification that contains @t.prop += val1, @t.prop += val2 constraints. Using <stx-get-ast-property(|a, "prop")> t will then return [val1, val2].

As the type and ref properties have special meanings in the Spoofax context, there are special strategies to retrieve those:

stx-get-ast-type(|a)

stx-get-ast-ref(|a)

which both have the same type constraints as stx-get-ast-property

type and ref properties

Using the generic stx-get-ast-property to retrieve type or ref properties will not work. I.e., stx-get-ast-property(|a, "type")> t will fail, even if there was an @t.type := T constraint.

## Scope Graph¶

Declarations in a scope graph can be retrieved using the following strategies:

stx-get-scopegraph-data(|a, rel)

stx-get-scopegraph-edges(|a, lbl)

Argument Type Description
a Analysis Analysis object for the given AST node.
rel String Fully qualified name of the relation that is queried.
lbl String Fully qualified name of the label that is traversed.

The stx-get-scopegraph-data strategy, which has type Scope -> [Term] retrieves all data declared under relation rel in the input term scope. The data is returned in a (possible empty) list that contains tuples holding the data of each relevant declaration.

Example. Consider a Statix specification that gives rise to a new s, !var["x", INT()] in s, !var["y", BOOL()] in s constraint. Now, applying <stx-get-scopegraph-data(|a, "statics/Main!var")> s will return [("x", INT()), ("y", BOOL())].

Note that a fully qualified name should be passed to the rel argument. Fully qualified names are created by prefixing a relation name with the module in which it is declared, separated by a !. For example, "statics/Main!var" is the fully qualified name of the relation var declared in module statix/Main. The Spoofax 2 Console will emit warnings when an invalid label is used, and suggest available names.

The returned values will be interpreted relative to the unifier of the analysis. That is, it will be instantiated as much as possible. When a property value contains free variables, those will occur in the property as nabl2.Var: String * String -> Term terms.

The stx-get-scopegraph-edges strategy, which has type Scope -> [Scope] traverses all edges with the lbl label. All target scopes are returned in the output list.

Example. Consider a Statix specification that gives rise to a new s s1 s2, s -L-> s1, s -L-> s2 constraint. Now, applying <stx-get-scopegraph-edges(|a, "statics/Main!L")> s will return [s1, s2].

Similar to the stx-get-scopegraph-edges strategy, the label should be fully qualified, and the result may contain free variables.

Retrieving a scope

Both strategies discussed in this section take a scope as input. However, it seemed that no way to obtain a reference to a scope was introduced. In fact, scope references should be made available using AST properties. For example, the new s, @t.scope := x makes scope s available using the stx-get-ast-property(|a, "scope") t transformation.

## Analysis Results¶

stx-analysis-has-errors = stx--analysis-has-errors


Type: Analysis -> Analysis

Fails if the current term has no errors, succeeds otherwise.

Last update: 2023-03-07