indexion kgf

Inspect and debug KGF language specs by viewing tokens, parse events, and extracted edges.

When to Use

• User wants to debug how indexion processes a specific file
• User is developing or modifying a KGF spec
• User asks "how does indexion parse this file?"
• Verifying that tokenization/parsing works correctly for a language
• Debugging grep patterns: when a grep pattern doesn't match, use

kgf tokens to see the actual token kinds

Subcommands

indexion kgf list — List Installed Specs

indexion kgf list

indexion kgf update — Update All Specs

Download the latest specs from GitHub.

indexion kgf update

indexion kgf add — Install a Single Spec

indexion kgf add <spec-name>

indexion kgf inspect — Full Inspection

Show tokens, events, and edges all at once.

indexion kgf inspect <file>
indexion kgf inspect --spec=typescript src/app.ts

indexion kgf tokens — Tokenization Only

Show how a file is tokenized.

indexion kgf tokens <file>
indexion kgf tokens --spec=go-mod go.mod

indexion kgf events — Parse Events Only

Show parse events generated from tokens.

indexion kgf events <file>

indexion kgf edges — Extracted Edges Only

Show the dependency edges extracted from a file.

indexion kgf edges <file>
indexion kgf edges fixtures/project/npm/package.json

Options

Relationship to grep

indexion grep uses KGF tokenization under the hood. Pattern aliases (pub → KW_pub) are derived from the === lex section of KGF specs.

When a grep pattern doesn't match as expected:

# 1. See the actual tokens for a file
indexion kgf tokens src/config/paths.mbt

# 2. Check which token kinds exist
indexion kgf tokens src/config/paths.mbt | head -20

# 3. Then adjust your grep pattern to match the actual token kinds
indexion grep "KW_pub KW_fn Ident" src/config/paths.mbt

Common token kinds (MoonBit):

• KW_pub, KW_fn, KW_struct, KW_enum, KW_type, KW_trait, KW_let, KW_for
• Ident (lowercase identifiers), TypeIdent (PascalCase type names)
• LPAREN, RPAREN, LBRACE, RBRACE, LBRACKET, RBRACKET
• NL (newline), SKIP (whitespace — filtered from grep patterns)
• DocComment, DocLine, DocSection, LineComment, BlockComment
• String, Number, Char

Workflow

1. Run indexion kgf inspect <file> to see the full processing pipeline
2. If something looks wrong, drill down with tokens, events, or edges
3. Compare with the KGF spec file (kgfs/<lang>.kgf) to diagnose issues

KGF Development Pitfalls

Common bugs found when writing or modifying KGF specs:

PEG Item Ordering (first-match-wins)

KGF uses PEG parsing. In Item -> A / B / C, if A matches, B and C are never tried. DocComment as a standalone alternative before declaration rules will consume doc comments that should be attached to declarations.

# BAD: DocComment before FuncDecl — doc is consumed as standalone item
Item -> NL / DocComment / FuncDecl / Other

# GOOD: DocComment after declarations — FuncDecl's doc:DocComment? gets it
Item -> NL / FuncDecl / DocComment / Other

NL Between Doc and Keyword

Source code has newlines between doc comments and declarations. Without NL? or NL*, the optional doc capture fails silently:

# BAD: DocComment immediately followed by keyword — NL breaks the match
FuncDecl -> doc:DocComment? KW_fn id:Ident ...

# GOOD: NL? allows the typical newline between doc and keyword
FuncDecl -> doc:DocComment? NL? KW_fn id:Ident ...

Bottom-Up Event Order (bind/scope)

Events fire bottom-up: child rules before parent rules. If ExportDecl wraps FunctionDecl, FunctionDecl fires first. Use bind/$scope to pass data from child to parent:

on FunctionDecl {
  bind ns "value" name "child_decl_id" to $id
  edge declares from $file to sym_id attrs obj(...)
}
on ExportDecl when $doc {
  let id = $scope("value", "child_decl_id")
  edge declares from $file to sym_id attrs obj("doc", $doc, ...)
}

Token Priority Conflicts

Tokens defined earlier take priority. A generic Operator /[=+\-*]+/ before EQ /=/ will consume = as Operator. Define specific tokens first:

# BAD: Operator matches = before EQ can
TOKEN Operator /[!$%&*+\-.\/:<=>?@^|~]+/
TOKEN EQ       /=/

# GOOD: EQ defined first, takes priority
TOKEN EQ       /=/
TOKEN Operator /[!$%&*+\-.\/:<=>?@^|~]+/

Verifying Doc Extraction

After modifying a KGF, always verify doc appears in declares edges:

# Must show doc="..." in the declares edge
indexion kgf edges test_file.ts --spec=typescript | grep declares

# If doc is missing, check events to see where the DocComment went
indexion kgf events test_file.ts --spec=typescript | grep DocComment