Debugging & Introspection

AshGrant provides tools for understanding authorization decisions and querying permissions at runtime.

Debugging with explain/4

Use AshGrant.explain/4 to understand why authorization succeeded or failed:

# Get detailed explanation
result = AshGrant.explain(MyApp.Post, :read, actor)

# Check the decision
result.decision  # => :allow or :deny

# See matching permissions with metadata
result.matching_permissions
# => [%{permission: "post:*:read:always", description: "Read all posts", source: "editor_role", ...}]

# See why permissions didn't match
result.evaluated_permissions
# => [%{permission: "post:*:update:own", matched: false, reason: "Action mismatch"}, ...]

# Print human-readable output
result |> AshGrant.Explanation.to_string() |> IO.puts()

Sample output:

═══════════════════════════════════════════════════════════════════
Authorization Explanation for MyApp.Blog.Post
═══════════════════════════════════════════════════════════════════
Action:   read
Decision: ✓ ALLOW
Actor:    %{id: "user-1", role: :editor}

Matching Permissions:
  • post:*:read:always [scope: always - All records without restriction] (from: editor_role)
    └─ Read all posts

Scope Filter: true (no filtering)
───────────────────────────────────────────────────────────────────

Read vs write scope evaluation

Scopes with exists() or dot-paths work for both reads and writes automatically:

• Read: FilterCheck lowers the expression to SQL.
• Write: Check evaluates it in memory where possible; for scopes with relationship references it falls back to a DB query.

For multi-hop write authorization (e.g., refund.order.center_id in actor_units), prefer argument-based scopes — they keep the scope expression in-memory-evaluable and push relationship traversal into the resource's own change pipeline:

ash_grant do
  scope :at_own_unit, expr(^arg(:center_id) in ^actor(:own_org_unit_ids))
  resolve_argument :center_id, from_path: [:order, :center_id]
end

See the Argument-Based Scope guide for the full pattern.

Resolution functions:

• AshGrant.Info.resolve_scope_filter/3 — resolved read filter (inheritance applied)
• AshGrant.Info.resolve_write_scope_filter/3 — resolved write filter (inheritance applied; respects the deprecated write: override for backward compatibility — see below)

write: option (deprecated)

The write: option was introduced as an escape hatch when the main filter could not be evaluated in memory on write actions. It is deprecated as of 0.14 — prefer argument-based scopes + resolve_argument for multi-hop cases, or use a separate scope name for read-only semantics.

Using write: still works but emits a compile-time deprecation warning.

Scope Descriptions

Add descriptions to scopes for better debugging output:

ash_grant do
  resolver MyApp.PermissionResolver

  scope :always, true, description: "All records without restriction"
  scope :own, expr(author_id == ^actor(:id)), description: "Records owned by the current user"
  scope :published, expr(status == :published), description: "Published records visible to everyone"
end

Access scope descriptions programmatically:

AshGrant.Info.scope_description(MyApp.Post, :own)
# => "Records owned by the current user"

Permission Introspection

The AshGrant.Introspect module provides runtime helpers for querying permissions:

Admin UI: What can this user do?

AshGrant.Introspect.actor_permissions(Post, current_user)
# => [
#   %{action: "read", allowed: true, scope: "all", denied: false, instance_ids: nil, field_groups: []},
#   %{action: "update", allowed: true, scope: "own", denied: false, instance_ids: nil, field_groups: []},
#   %{action: "destroy", allowed: false, scope: nil, denied: false, instance_ids: nil, field_groups: []}
# ]

Permission Management: What permissions exist?

AshGrant.Introspect.available_permissions(Post)
# => [
#   %{permission_string: "post:*:read:always", action: "read", scope: "all", scope_description: "All records", field_group: nil},
#   %{permission_string: "post:*:read:own", action: "read", scope: "own", scope_description: "Own records", field_group: nil},
#   ...
# ]

Note: available_permissions/1 requires inline scope definitions in the DSL. Resources using scope_resolver will return an empty list.

Debugging: Can user do this action?

AshGrant.Introspect.can?(Post, :read, user)
# => {:allow, %{scope: "all", scopes: ["all"], instance_ids: nil, field_groups: []}}

AshGrant.Introspect.can?(Post, :destroy, user)
# => {:deny, %{reason: :no_permission}}

API Response: What actions are available?

# Simple list
AshGrant.Introspect.allowed_actions(Post, user)
# => [:read, :create, :update]

# With details
AshGrant.Introspect.allowed_actions(Post, user, detailed: true)
# => [
#   %{action: :read, scope: "all", instance_ids: nil, field_groups: []},
#   %{action: :create, scope: "all", instance_ids: nil, field_groups: []},
#   %{action: :update, scope: "own", instance_ids: nil, field_groups: []}
# ]

Raw Permission Access

AshGrant.Introspect.permissions_for(Post, user)
# => ["post:*:read:always", "post:*:update:own", "post:*:create:always"]

With Context

All functions accept a :context option for passing additional resolver context:

AshGrant.Introspect.actor_permissions(Post, user, context: %{tenant: tenant_id})

Identifier-Based Introspection

The functions above all take a hydrated actor struct. External tools — admin dashboards, CLI commands, LLM agents, webhook handlers — often have only an actor ID plus string keys for the resource and action. The identifier-based variants take strings/IDs and do the lookup work themselves.

Provisional (v0.15): signatures may tighten in a minor release. See Public API Contract for stability tiers.

Opt in: implement load_actor/1 on your resolver

The identifier-based functions call your resolver module's optional load_actor/1 callback to turn an ID into an actor. Implementing it is how a resolver declares it can be driven by ID:

defmodule MyApp.PermissionResolver do
  @behaviour AshGrant.PermissionResolver

  @impl true
  def resolve(actor, _context), do: actor.permissions

  @impl true
  def load_actor(user_id) do
    case MyApp.Accounts.get_user(user_id) do
      nil -> :error
      user -> {:ok, user}
    end
  end
end

Existing resolvers without load_actor/1 keep working — the identifier-based functions return {:error, :actor_loader_not_implemented} and the rest of the API is unchanged.

explain_by_identifier/1

Resolves the resource by key, loads the actor, and delegates to AshGrant.explain/4:

AshGrant.Introspect.explain_by_identifier(
  actor_id: "user_1",
  resource_key: "post",    # matches AshGrant.Info.resource_name/1
  action: :read,
  context: %{tenant: "acme"}  # optional
)
# => {:ok, %AshGrant.Explanation{decision: :allow, ...}}

can_by_identifier/3

AshGrant.Introspect.can_by_identifier("user_1", "post", :read)
# => {:allow, %{scope: "always", scopes: ["always"], instance_ids: nil, field_groups: []}}

AshGrant.Introspect.can_by_identifier("user_1", "post", :destroy)
# => {:deny, %{reason: :no_permission}}

actor_permissions_by_id/2

AshGrant.Introspect.actor_permissions_by_id("user_1", "post")
# => {:ok, [%{action: "read", allowed: true, ...}, ...]}

Error returns

All three never raise for predictable lookup failures. They return:

CLI: mix ash_grant.explain

A thin wrapper around explain_by_identifier/1 for shell scripts and CI checks:

mix ash_grant.explain --actor USER_ID --resource RESOURCE_KEY --action ACTION \
  [--format text|json] [--context '<json>']

Exit codes:

Stringifying Scope Expressions

Provisional (v0.15).

Ash's default expression inspect is readable but uses internal references like {:_actor, :id} instead of the DSL-facing ^actor(:id). AshGrant.ExprStringify.to_string/1 produces the human-facing form — the same form users write in their ash_grant do blocks.

expr = AshGrant.Info.resolve_scope_filter(MyApp.Post, :own, %{})
AshGrant.ExprStringify.to_string(expr)
# => "author_id == ^actor(:id)"

AshGrant.ExprStringify.to_string(true)   # => "true"
AshGrant.ExprStringify.to_string(nil)    # => "nil"

Mappings:

Contract:

• Always returns a binary.
• Never raises — unknown terms fall back to inspect/1.
• Display-only. The output is not round-trippable back into an expression.

The same function populates Explanation.scope_filter_string, so JSON consumers (LLM tools, dashboards) always receive a printable form without having to carry the raw AST.