[Query] Happens Before

This document was generated from 'src/documentation/wiki-query.ts' on 2026-07-20, 13:05:03 UTC presenting an overview of flowR's query API (v2.12.3). Please do not edit this file/wiki page directly.

Happens-Before Query ^[overview]

Check whether one normalized AST node happens before another in the CFG.
This query is requested with the type happens-before.

With this query you can analyze the control flow graph:

Using the example code:

x <- 1
y <- 2

the following query returns that the first assignment happens always before the other:

[
  {
    "type": "happens-before",
    "a": "1@x",
    "b": "2@y"
  }
]

Results (prettified and summarized):

Query: happens-before (1 ms)
   ╰ 1@x<2@y: always
All queries together required ≈1 ms (1ms accuracy, total 2 ms)

Show Detailed Results as Json

The analysis required 1.9 ms (including parsing and normalization and the query) within the generation environment.

In general, the JSON contains the Ids of the nodes in question as they are present in the normalized AST or the dataflow graph of flowR. Please consult the Interface wiki page for more information on how to get those.

{
  "happens-before": {
    ".meta": {
      "timing": 1
    },
    "results": {
      "1@x<2@y": "always"
    }
  },
  ".meta": {
    "timing": 1
  }
}

Original Code

x <- 1
y <- 2

Dataflow Graph of the R Code

The analysis required 1.4 ms (including parse and normalize, using the r-shell engine) within the generation environment. No signature database is mounted for these generated graphs, so library() calls attach no package exports; base-R names are still qualified via the generated base-package store (e.g. acf as stats::acf). We encountered no unknown side effects during the analysis.

flowchart LR
    1{{"`*#91;RNumber#93;* **1**
      *1.6* (**id: 1**)`"}}
   %% No edges found for 1
    0["`*#91;RSymbol#93;* **x**
      *1.1* (**id: 0**, v: 1)`"]
    2[["`*#91;RBinaryOp#93;* base#58;#58;**#60;#45;**
      *1.1-6* (**id: 2**)
    arg: (0, 1)`"]]
    built-in:_-["`Built-In:
#60;#45;`"]
    style built-in:_- stroke:gray,fill:gray,stroke-width:2px,opacity:.8;
    4{{"`*#91;RNumber#93;* **2**
      *2.6* (**id: 4**)`"}}
   %% No edges found for 4
    3["`*#91;RSymbol#93;* **y**
      *2.1* (**id: 3**, v: 4)`"]
    5[["`*#91;RBinaryOp#93;* base#58;#58;**#60;#45;**
      *2.1-6* (**id: 5**)
    arg: (3, 4)`"]]
    0 -->|"defined-by"| 1
    0 -->|"defined-by"| 2
    2 -->|"reads, arg"| 1
    2 -->|"returns, arg"| 0
    2 -.->|"reads, calls"| built-in:_-
    linkStyle 4 stroke:gray;
    3 -->|"defined-by"| 4
    3 -->|"defined-by"| 5
    5 -->|"reads, arg"| 4
    5 -->|"returns, arg"| 3
    5 -.->|"reads, calls"| built-in:_-
    linkStyle 9 stroke:gray;

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Implementation Details

Responsible for the execution of the Happens-Before Query query is executeSearch in ./src/queries/catalog/happens-before-query/happens-before-query-executor.ts.